Enzymatic degradation of polyethylene terephthalate

Abstract

The present disclosure provides variant enzymes for use in the enzymatic degradation of polyethylene terephthalate (PET).

Description

[0001]ENZYMATIC DEGRADATION OF POLYETHYLENE TEREPHTHALATE BACKGROUND OF THE INVENTION The use of polyethylene terephthalate (PET) is widespread and ubiquitous. As such, PET is a major source of environmental pollution globally. Physical recycling is possible but underused in many settings. Enzymatic degradation has been explored in the last decades but has proven challenging. Provided herein are variant enzymes for use in the enzymatic degradation of PET. BRIEF SUMMARY OF THE INVENTION In one aspect, the present disclosure relates to a composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises a C-terminus having at least 96% identity to SEQ ID NO:7 and has PETase activity. In another aspect, the present disclosure related to a composition comprising a variant Bhr-PETase as compared to SEQ ID NO: 5, wherein said variant comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258, wherein said variant Bhr-PETase has at least 85% identity to SEQ ID NO:5 and has PETase activity. In another aspect, the present disclosure relates to a composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258, wherein said variant Bhr-PETase has at least 85% identity to SEQ ID NO:5 and has PETase activity. In another aspect, the present disclosure relates to a composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258, wherein said variant Bhr-PETase has at least 95% identity to SEQ ID NO:5 and has PETase activity. In another aspect, the present disclosure relates to a composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258, wherein said variant Bhr-PETase has at least 95% identity to SEQ ID NO:5 and has PETase activity equal to or greater than G3P Bhr-PETase, SEQ ID NO:5. In some embodiments, said amino acid substitution above is at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258. In some embodiments, said amino acid substitution above is at an amino acid position(s) selected from the group consisting of 89, 91, 118, 176, 214, 215, 248, 256, and 257. In some embodiments, said amino acid substitution is selected from the group consisting of V177I, V177T, V170I, V170L, T206D, A216T, R12E, R12F, R12S, R12T, D203A, D203C, D203E, D203G, D203L, D203S, D203Y, F92D, S212E, S212H, S212I, S212Q, S212T, N211Q, P213A, Q182D, Q182E, Q182S, T206S, A174G, A209E, A216E, A216I, A246E, A246N, A246Q, D249L, E173A, E173D, E173N, E173P, E173T, E173V, E173W, I217M, L90A, N204G, N254F, Q258K, R12L, R12M, R12Q, S181D, S181Q, S181T, T157D, T157E, T157L, T157Q, T157S, T160M, V177W, D203K, D203N, D203R, D203V, F92G, F92Q, P213N, E173R, H156N, L90F, L90Y, N204S, N253S, R255W, S181A, T157A, T157G, T176S, R118C, C257P, R89I, R89K, R89M, N214D, A215D, A215K, A215S, S248C, S248R, H256V, A14V, N87K and D91N. In some embodiments, said amino acid substitution is selected from the group consisting of T176S, R118C, C257P, R89I, R89K, R89M, N214D, A215D, A215K, A215S, S248C, S248R, H256V and D91N. In some embodiments, said variant Bhr-PETase enzyme has one or more amino acid substitutions at one of said positions, two of said positions, three of said positions, four of said positions, five of said positions, six of said positions, seven of said positions, eight of said positions, nine of said positions, ten of said positions, eleven of said positions, twelve of said positions, thirteen of said positions, fourteen of said positions, fifteen of said positions, sixteen of said positions, seventeen of said positions, eighteen of said positions, nineteen of said positions or twenty of said positions. In some embodiments, said variant Bhr-PETase comprises a set of amino acid substitutions selected from the group consisting of A174G / P213A, D203K / A215S, E173W / Q182E, L90Y / A174G, L90Y / T176S, R118C / Q182D, R12E / D203R, R12F / T157Q, R12Q / D203L, R12Q / T176S, R12T / R89K, R89I / T160M, R89K / L90F, T176S / N211Q, V170I / Q182E, A174G / D203A / A216E, A174G / P213N / N214D, D203G / A216E / I217M, E173N / S181D / S212E, F92G / E173V / T206D, F92G / T157Q / V170I, L90F / N211Q / S212T, R12E / T157L / A215S, R12E / T157L / A246E, R12Q / T157L / A174G, S181A / Q182S / D203S, T176S / D203A / A216I, V170I / A215D / A216T, V170I / E173T / S181D, A174G / T176S / D203G / A215D, L90F / E173R / A174G / V177W, L90F / F92Q / E173D / P213A, L90Y / A174G / T176S / A216E, L90Y / T176S / V177I / D203E, R12E / V170I / V177T / S212H, R12M / V170L / A174G / S181D, R12Q / T157L / T176S / V177I, R12T / V170I / T176S / V177T, R89I / A174G / T176S / A215K, R89I / L90F / E173D / S181A, R89M / T157G / S181T / Q182E, T157G / V170I / S181T / S212Q, T157Q / V170I / S181D / S212H, V170I / T176S / V177T / A246E, L90F / F92G / V170I / T176S / V177T, L90Y / A174G / T176S / V177I / Q182E, L90Y / F92Q / N204G / N211Q / A215S, L90Y / T157Q / V170I / S181Q / Q182D, R12E / L90F / V177I / D203C / A216I, R12E / R89K / L90F / V170I / T176S, R12F / V170L / T176S / V177I / S181D, R89I / L90Y / H156N / T157L / V177I, T157Q / V170L / S181T / Q182D / D249L, V170I / S181Q / Q182E / D203Y / A215D, V170L / S181D / Q182E / S212H / A246E, L90Y / V170I / T176S / V177I / Q182D / A246E, R12E / E173R / S181T / T206D / S212E / A246N, R12F / L90F / F92G / E173V / S181T / Q182D, R12M / A174G / S181T / Q182D / T206D / S212H, R12T / V177T / D203V / A215D / A246N / S248C, T157E / V170L / V177I / Q182E / A215D / A246N, T157Q / V170L / T176S / V177T / A215D / A216T, V170I / T176S / V177T / S181D / D203K / S212E, V170L / A174G / T176S / Q182D / S212Q / A246E, F92G / T157L / V170I / T176S / S181Q / Q182E / S212H, L90F / F92D / V170L / T176S / D203S / T206D / S212H, L90Y / F92G / Q182S / N211Q / S212I / A216E / I217M, L90Y / H156N / T157L / T176S / N204G / T206S / A215D, L90Y / V170I / V177T / D203Y / S212E / A246E / S248C, R12F / V170L / V177I / S181D / Q182E / S212E / A246E, R12L / R89K / L90Y / V170I / V177I / S181Q / Q182D, R12T / R89K / L90F / V170L / T176S / S181Q / A216T, R12T / T157Q / V170I / A174G / T176S / A215D / A216T, F92G / T157E / A174G / T176S / V177W / S181D / A215D / A216T, R12F / T157E / T176S / V177I / S212E / A215D / A216T / A246Q, R12M / R89K / L90Y / V170L / T176S / V177I / T206D / S212H, R89I / L90Y / T176S / S181A / Q182S / N204S / P213A / N214D, E173N / Q182D / A246Q / N253S / N254F / R255W / H256V / C257P / Q258K, L90Y / F92G / T157G / V170I / T176S / V177I / D203A / S212Q / A246E, R12F / L90F / T157G / E173R / A174G / Q182E / D203N / A216T / A246Q, L90Y / T157S / V170L, R12S / L90F / T157L / V170I / S181T / Q182D / A216T / A246E / S248R, R12T / T157L / V170L / V177T / D203S / A215D, R12S / R89K / T157L / V170I / T176S / S181D / Q182D / D203G / A216T, R12S / R89K / L90Y / T176S / V177I / Q182D / D203A, R12T / R89K / V170I / V177T, R12E / L90Y / T157L / E173A / A215D / A216T / A246E, R12E / L90Y / V170I / E173T / Q182D / A215D / A246E, R12E / V170I / V177T / D203R, R12E / V170L / T176S / A215D, R12E / L90Y / V170I / A174G / V177I / S181D / A215D / A216T / A246E / S248R, R12E / V170L / D203R / A246E, V170L / V177T / A246E, R12T / L90Y / V170I / D203G, R89K / L90Y / V177I / S181D / D203G / A215D / A216T, R12E / A216T, R12E / E173T / Q182D, R12E / E173A / A174G / S181T / Q182D / A216T, R12E / L90F / F92G / E173A / S181D / D203R, R12S / V170L / T176S / S181D, R12E / T176S / D203R / A246E, L90Y / V170I / T176S / V177T / S181D / D203R / A246E / S248R, R12E / V177I / D203R, R12S / V170I / T176S / V177T / S181D / Q182D / A246E, L90Y / E173P / A174G / S181D / D203G, R12E / D203K / A246E, R12T / L90F / E173A / A174G / S181D / A216T / D249L, L90Y / V170I / T176S / V177I / S181D / Q182D / A246E / S248C, R12T / R89K / L90Y / T157A, V170I / T176S / V177T / D203R / A246E / S248R, R12T / L90Y / V170L / V177I / A216T, L90Y / V170I / V177T / A216T, L90Y / F92G / T157A / V170I / D203G / A216T / A246E / S248C, R12T / L90Y / V170L / T176S / V177T / D203R / A216T, F92G / V170I / V177I / S181D, R12E / L90Y / V170I / T176S / S181T / D203R / A216T / A246E, R12T / D203R / D249L, L90Y / V170L / T176S / V177I, L90Y / V170L / V177T / D203G / A216T / A246E, L90Y / A246E, F92G / T157L / E173T / S181T / Q182D / A246E / S248C, L90F / F92G / V170I / V177T / D203R / A216T, R12S / E173P / S181T / D203R / A215D / A216T / A246E, R12E / F92G / A215D / A216T / A246E / S248R, R12E / L90A / E173P / A174G / S181T / Q182D / A215D / A216T, L90Y / D249L, F92G / T157A / E173P / A174G / S181D / A216T, L90F / D203R / D249L, R12T / L90Y / E173P / A174G / A246E, R12E / V170I / A174G / Q182D / D203R / A215D / A216T, R12E / E173P / S181T / Q182D / A215D / A216T, R12S / L90Y / S181T / Q182D / D203R, R12E / V170L / D203R / A215D / A246E, R12T / L90Y / V170L / A215D, R12E / F92G / V170I / A174G / T176S / D203R / A216T, R12E / V170I / E173P / S181T / D203R, R12T / T157S / E173P / A174G / S181D / D203R / A246E / S248R, R12E / L90Y / V170L / A174G / S181T / Q182D, R12E / S181T / Q182D / D203R / A215D, R12E / T157L / A215D, R12S / V170I / V177T / D203R, R12T / L90Y / V170L / D203A, R12E / T176S / V177T / D203R / A215D, R12S / V170I / Q182D / A215D / A216T, R12T / L90Y / V170I / V177T, R12S / R89K / L90A / V170I / A174G / T176S / S181D / Q182D, R12E / V170L / S181D / A215D, R12T / T157E / V170L / T176S / S181T / D203R / A215D / A246E, R12E / L90Y / T157A / E173A / S181T / Q182D / A215D / A216T, R12E / N87K / R89K / V170I / T176S / V177I / D203R / A215D / A216T / D249L, R12E / V170I / T176S / V177I / S181D / Q182D, R12T / L90F / V170I / S181D, R12T / L90Y / V170L / T176S / V177T / D203R / A246E, R12E / F92G / T157E / E173A / A174G / S181T / Q182D, R12E / F92G / V170I / T176S / V177T / A215D / A216T / A246E, R12T / V170I / T176S / V177T / D203R, R12E / L90Y / E173P / A174G / S181T / Q182D, R12E / T157D, R89K / L90F / T157A, R12E / L90Y / T157L / V170L / T176S / V177T / S181D / Q182D / D203R / A246E, R12S / V170L / T176S / V177I, R12E / L90F / F92G / V170L / V177T / D203R / A216T, V170I / A174G / S181D / D203R / A246E / S248R, V170I / S181T / Q182D, R12E / T157E / T176S / Q182D / A215D / A216T, R12S / V170I / S181D / D203R / A215D / A216T, R12E / L90A / F92G / V170L / S181T, R12E / L90Y / T157E / D203K / A246E, R12E / R89K / L90F / T157L / E173A / A174G / S181T / Q182D / A216T / A246E, R12E / V170L / T176S / S181D / Q182D / A216T, R12E / R89K / L90Y / D203R, R12S / T157S / E173T / A174G / D203R / A215D, R12E / F92G / T176S / V177I, R12T / V170L / T176S / V177T / D203R / A216T, R89K / V170L / T176S / V177I / A215D, R12T / V170I / D203A / S212H, R12F / T157L / V170I / T176S / D203A / S212E, R12S / E173V / A174G / S181Q / Q182D, V170L / S181Q / Q182D, R12E / V170L / V177I / A246Q / S248R, T157Q / V170L / E173R / S181Q / Q182E / S212H, L90F / V170I / T176S / V177I / Q182D / A216T, T157Q / E173V / A174G / S181T / Q182D, R12T / L90F / F92G / V170I / A215D, E173R / A174G / Q182D, R12E / T157L / E173N / A174G / S181D / Q182D, L90F / V170L / T176S / V177T / A215D, R12L / F92G / T157E / V170L / S181T / Q182D / T206D / S212Q / A246Q, R12M / V170I / T176S / V177I / S212Q, V170I / T206D / S212Q, E173R / A174G / A209E / A215D / A246Q, L90F / V170I / Q182E / A215D, T157G / V170I / Q182E / D203V, R12S / R89K / L90F / E173P / Q182D / A246E, R12T / A174G / T176S, R12T / V170I, T157S / E173T / A174G / S181T / Q182E / A215D / A246N, R12F / L90Y, V170L / V177T / T206D / A215D, R12E / T157L / A246N, V170I / A174G / T176S / Q182E / T206D / A216T, D203L / S212H / D249L, L90Y / E173N / S181T / Q182E, R12T / Q182D / A215D / A216T, L90F / F92G / A246Q, L90A / T157S / V170L / V177I / T206D / S212Q, T157E / V170L / V177I / T206D / A209E, E173A / S181Q, E173N / S181D / D203G / A209E / A215D / A216T, E173V / A174G, R12S / L90Y / A246N / S248R, S212H / A246E, L90F / F92G / T157Q / V170I / V177W / A209E / A215D / A216T, R12S / V170L / A215D / A216T / A246E, R12T / L90A / E173P / A174G / S181D / Q182E, T157G / A209E / A215D / A246Q, T157S / V170I / V177T / S181T / Q182D / D203S / S212E / A246Q / S248C, T157D / V170L / A174G / V177W / T206D / S212H / A246E, F92G / T157Q / E173R / A174G / S181D / Q182D / A215D / A216T / S248R / D249L, R89M / L90F / T206D, R12F / R89K / V170I / A216T / S248C, R12E / T157Q / V170L / V177I / S212E / A216T / A246E, R12T / R89K / L90A / E173R / A174G / S181T / Q182D / A215D / A216T, R12F / A174G / Q182E / A209E / A216T, R12S / E173R / S181T / Q182D / T206D / A216T / A246E, R12T / L90A / D203Y / A209E / S212Q / A246Q, R12M / E173P / A174G / S181D / A209E / S212Q / A246E / S248R, R12T / R89K / L90Y / S212H / A215D / A246Q / S248C, R12T / R89K / L90A / A174G / T176S / S181T / Q182D / A215D / A246Q, R12M / S212H / S248C / D249L, R89K / L90F / A174G / S181D / S212E / A246E / S248C, R12L / R89K / L90Y / T157D / E173P / A174G / S181Q / Q182D / S212H, R12T / R89K / L90A / A215D / A216T / D249L, R12M / V170L / T206D / S212E / S248C / D249L, E173R / Q182D / A215D / A216T / S248R / D249L, R12L / A209E / A216T / A246Q / S248R, R89K / L90Y / T176S / V177W / D203Y / A216T, R12M / L90F / A174G / A246N / S248C, R12M / V170I / A174G / T176S / S181T / T206D / A246Q / S248C, A174G / D203G / A216T / S248C / D249L, R12E / L90A / E173R / S181Q / Q182E / A209E / S212Q / A246N / S248C, R12T / T157Q / V170L / T176S / V177T / T206D / A209E / A216T, R89K / L90Y / T206D / A209E / S212H / S248C, R12T / R89K / L90Y / A216T, R12S / V170L / A209E / A216T / A246E, R89K / T176S / V177I / S181Q / T206D / A209E / A215D / A216T / A246E, V170L / E173N / V177T / Q182D / T206D / A216T / A246Q, R12T / Q182E / D203V / A216T / A246E / S248C, R89K / L90Y / V170L / A174G / T176S / S181Q / S212E / A215D / A216T / A246E, R12T / L90A / T176S / S212E, A216T / S248C, A216T / A246Q / S248C, T157Q / V170L / T176S / Q182D / A209E / A216T / A246Q, R12E / T157Q / E173R / A174G / Q182E / D203L / N204G / S212Q / A246E / S248C, V170L / V177W / S181Q / Q182E / A209E / A216T / A246E, L90A / S212Q / A246E / S248C, L90F / S212E / A246E / S248C, R89K / L90Y / E173T / S181T / N204G / T206D / A215D / A246N / S248C, R12S / A216T / S248C, R12L / V170L / T206D / A209E / A215D / A216T / D249L, T157D / E173P / A174G / Q182E / T206D / A215D / A216T, R12F / E173R / S181T / A246E / S248C, R12F / T157D / V170L / A209E / A216T, T176S / V177W / A246N / S248C, R89K / L90A / E173W / A215D / A216T / A246E / S248C, L90Y / T157G / A174G / T176S / A216T / A246Q / S248C, S212E / A246E, S212E / A246E / S248C, V170L / A209E / A216T / D249L, R12L / V170L / V177T / D203K / S212H / S248C / D249L, R12T / V170L / T176S / V177T / A209E, R12T / L90Y / F92G / V170I / V177I / S212E / A246Q / S248C, R12E / R89K / L90A / V170I / V177I / T206D / A215D / A216T, E173T / S248C / D249L, L90Y / E173V / S181D / T206D / S212Q / A246Q, D203K / A246E, T157G / V170L / T206D / A209E, L90A / E173P / A174G / S181T, A174G / T176S / A246N / S248R, L90F / F92G / D203S, V170I / T176S / V177W, V170L / V177I / S181T / Q182D / T206D / A209E / A215D / A216T, R12M / L90F / F92G / V170I / S181T / Q182D / S212E, R12M / A14V / V170I / V177T / S212H / A246E / S248C, R12L / L90A / D91N / F92G / A215D / A216T, R12L / F92G / V170I / S181T / T206D / S212H, R12T / V170L / S181T / Q182D, T157A / D203V / A209E / A215D, T157G / E173R / A246E, T157L / V170I / V177I / S212H, V170I / T176S / V177I / Q182D / N204G / T206D, V170I / V177W / A209E / A216T, V177I / A215D / A216T, V177I / A216T, A215D / A246E, R89K / V170I / T176S / V177I / D203S, R12E / E173A / V177T / A215D / A216T, V170L / T176S / Q182D, T157L / E173A, R12T / E173A / A174G / S181T / Q182D, R12E / L90F / V170I / T176S / S181T / Q182D, R12E / T157E / V170I / A174G / T176S / Q182D, R12E / E173A / A174G / A216T / A246E, R12T / E173T / A174G / S181D / Q182D, R12E / A215D / A216T / A246E, R12T / R89K / L90Y / T157A / V170I / A174G / T176S, R12E / A174G / S181T / Q182D, R12S / V170L / A174G / S181D, V170I / Q182D, L90F / A215D / A216T, L90F / A215D / A246E, R12S / E173P / S181D, R12S / A215D / A216T / S248C, V170I / E173T / S181T / Q182D / D203G / A215D / A246E, R12T / R89K / L90F / V170I / S181D / Q182D / D249L, T157A / V170I, A174G / T176S / A246E, R89K / L90F / V170I / V177T, F92G / T157L / V170I / Q182D, V170L / V177T, L90Y / V170I / V177I / A215D / A216T, R89K / L90Y / T157S / A174G / S181T / Q182D, V170L / T176S / A215D, F92G / V170L, V170I / V177T, V170L / T176S / V177I / S181D / D249L, E173T / A174G / Q182D / D203G / A216T, E173P / S181T / D203R / A216T / A246E / S248C, T157A / V170L / V177T, R12S / A246E, T157L / Q182D / A216T / A246E, L90F / E173T / A216T, R12T / A174G / S181T / Q182D / A246E / S248R, T157S / V170L / V177I, R12S / L90Y / V170I / E173A / A174G / S181T / Q182D / S248C / D249L, R12T / R89K / L90Y / Q182D / A246E / S248C, R12E / F92G / V170L / V177T / A215D / S248C, R12T / L90A / A246E / S248C, R12S / A216T, R12T / S181D / Q182D / A216T / A246E, T157D / A174G / S181T / Q182D / A216T, R12T / S248C / D249L, E173P / A174G / S181T / Q182D, T157S / E173A / S181D / S248R / D249L, L90F / E173P / A174G / A216T, F92G / T176S / A216T, L90Y / E173A / A174G / S181T / Q182D / A216T, F92G / V170I / A174G / T176S / D203N / A215D / A216T / A246E, L90F / F92G / A246E / S248R, T176S / V177T / A215D / A246E, R12F / T157Q / V170I / D203G / S212Q / D249L, R89K / L90F / T176S / V177I, L90F / T157E / V170I / T176S / V177I / S212H, E173T / S181D / D203N, V170I / T176S / D203K, V170I / V177I / T206D / A215D, R12S / Q182E / D203S / A216T, T157Q / V170I / V177T / T206D / S212Q / D249L, T157D / T176S / V177T, E173P / S181D, R12M / T157S / V170L / T176S / V177T / S181D / Q182D, L90Y / E173R / Q182D / N204G / T206D / S212H, R89K / E173V / S181Q, L90F / F92G / V170I / S181Q / Q182D / T206D / A215D, S181T / Q182E / A216T, R12T / L90A / E173N / A209E, R89K / L90F / T157E / S181T, T206D / S212H / A246E, E173P / A174G, R12T / T157Q, E173R / A174G / Q182D / A216T / A246Q, T157Q / V170I / V177T / A246E, R12T / L90F / E173R / S181Q / Q182E / A209E, R12L / R89K / L90Y / V170L / T176S / V177I / N204G / A215D, R12T / R89K / L90Y / V170I, R89K / V170L / T176S, T157S / S212Q, V170L / A209E / S212E, R12T / R89K / T157G / D203N / S212E / A246E, E173R / A174G / Q182D / D203R / A215D / A216T / A246N / S248C, R12T / V170L / V177T / S181T / A216T, R12M / E173R / S181T / Q182E / S212Q / A216T, R12S / V170I / T206D / A209E / A216T / A246E, R12T / T157Q / V170I / E173N / S181T / Q182D / A215D / A216T / A246Q / S248C, R12T / V170L / V177T / A216T, R12L / T157E / V177I / Q182E / S212H / A246N, R12L / R89K / L90Y / V170I / V177I / D203R, R12M / T157E / T206D / S212E, V170I / E173P / S181D / Q182E / A216T, R12S / F92G / V170L / T176S / A209E / A215D / A216T, R12S / L90F / F92G / T157E / V170I / T206D / A246E, V170L / T176S / V177I / S181T / Q182D / D203A / S212E, F92G / V177W / A215D / A216T, V170I / T176S / S181Q / Q182E / T206D / S212Q, T157G / S212E, L90Y / V170I / T176S / N204G / A216T, T157L / V170I / V177T / S181D / S212E, F92G / V170I / V177T, E173N / T176S / S181T / Q182D / A246E, T157G / E173A / S212E / A246E, T157Q / V170I / T176S / T206D / A215D / A246N / S248C, and T157A / A174G / T176S / S181D / Q182D / A215D / A216T. In another aspect, the present disclosure relates to a nucleic acid encoding the variant Bhr-PETase enzyme of any one of the preceding claims. In another aspect, the present disclosure relates to an expression vector comprising the nucleic acid. In another aspect, the present disclosure relates to a host cell comprising the expression vector. In some embodiments, the cell is bacteria, yeast or fungi. In another aspect, the present disclosure relates to a method of making a variant Bhr-PETase enzyme comprising culturing the host cell described herein under conditions wherein said variant Bhr-PETase enzyme is produced, and recovering said variant Bhr-PETase enzyme. In another aspect, the present disclosure relates to a method of pretreating PET, comprising a mechanical pretreatment, a thermo-mechanical pretreatment, and / or a chemical pretreatment of the PET prior to an enzymatic degradation of the PET. In some embodiments, the mechanical pretreatment comprises grinding of the PET into particles. In some embodiments, the thermo- mechanical pretreatment comprises extruding the PET at a temperature configured to amorphize and reduce crystallinity of the PET. In some embodiments, the chemical pretreatment comprises contacting the PET with an ionic liquid, strong acid, base, or solvent configured to reduce crystallinity or to change a surface structure of the PET. In another aspect, the present disclosure relates to a method of degrading PET, comprising contacting the PET with the variant Bhr-PETase enzyme described herein. In some embodiments, the method further comprises pretreating the PET according to the method described herein. In some embodiments, the method degrades the PET in a mixed plastics composition. In some embodiments, the plastics composition comprises analog of PET, PET-like or PET substitute derived biologically or chemically. In some embodiments, the plastics composition comprises at least one selected from the group consisting of Polybutylene terephthalate (PBT), Polycabonate (PC), Polycaprolactone (PCL), Polyethylene Furanoate (PEF), and High Density Polyethylene (HDPE). In some embodiments, the method excludes sorting plastics to select PET from a mixture of plastics. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts the sequence of an exemplary wild type Bhr-PETase (also called G1P Bhr-PETase herein; SEQ ID NO:1). Figure 2 depicts the sequence alignment of the Bhr-PETase G1P (SEQ ID NO:1), Bhr-PETase G2P (SEQ ID NO:3), and Bhr-PETase G3P (SEQ ID NO:5). Figure 3 depicts the comparative analysis of protein titers among Bhr-PETase G1P, G2P, and G3P. Figures 4A-4F depict the tabulated fold improvement in PET degradation total activity of G3P derived variants. Figures 5A-5K are summary tables for G3P derived variants showcasing fold improvement in PET degradation total activity, protein titer, and / or PET degradation specific activity. Figure 6 depicts particular variants of Bhr-PETase by position that demonstrate beneficial properties in PET degradation total activity, protein titer, and / or PET degradation specific activity as displayed in Figures 4A-4F and Figure 5A-5K. Figures 7A-7B show the Sequence listing for G1P, G2P, G3P, G3P C-terminal, G3P linker and wild-type HFB4. Figures 8 shows the fold improvement in TPA %Conversion with engineered G3P C-terminal compared to wild-type HFB4. DETAILED DESCRIPTION OF THE INVENTION A. Introduction. The present invention is directed to enzymes that will hydrolyze polyethylene terephthalate (PET). PET is a polyester polymer created by the combination of two monomers: modified ethylene glycol and purified terephthalic acid. While plastics such as PET find literally thousands of uses in modern society, PET is essentially non-degradable. As such, plastic pollution has contaminated the entire planet, which poses a number of significant issues for the planet and human health. PET can be recycled; this however does not prevent major amounts of PET from being dumped into landfills and / or the ocean. Plastics including PET are remarkably resistant to enzymatic degradation. There are two categories of PET hydrolases: (i) PET-modifying enzymes that limit the degradation only at the surface of PET without visible change by electron microscopic observations, and (ii) PET-degrading enzymes or PETases that can significantly degrade the inner block of PET (e.g., by at least 10%) with visible change by electron microscopic observations. To date, a plethora of PET-modifying enzymes have been reported but they may not significantly degrade the body of PET and may not be applicable for biorecycling of PET. As is known in the art, there are a few enzyme types that show limited ability to degrade the inner block of PET. The first reported enzyme able to act on ester bonds of PET polymers was a cutinase from Thermobifida fusca in 2005. Subsequent work identified additional enzymes, including a PET-hydrolyzing enzyme from Ideonella sakaiensis (Is-PETase) in 2016, and a leaf branch compost cutinase (Lcc-PETase) in 2012. While these PETases show activity at ambient temperatures, these enzymes are not particularly thermostable and do not show robust PET degradation. PET exists both as an amorphous and as a semi-crystalline material. Chain mobility may be increased in the amorphous phase around PET’s glass transition temperature Tg (around 70°C), which allows better access to ester linkages and hence faster degradation. The reaction temperature around Tg may be controlled to achieve efficient enzymatic PET degradation. In addition, the physical aging process of PET at around 70°C may convert the mobile amorphous fraction to recalcitrant microstructures which hinders further enzymatic hydrolysis of PET. Therefore, a thermostable and thermoactive PETase is desirable to allow the degradation reaction to occur at around glass transition temperature and overcome the competing physical aging process. Figure 3 illustrates the remarkable improvements achieved with the engineered G3P Bhr-PETase, characterized by the S27L mutation and a novel C-terminal design, outperforming both the G1P wild- type and G2P (S27L mutation) variants in terms of protein titer. Furthermore, Figure 8 showcases the enhanced TPA %Conversion observed when the engineered G3P C-terminal is covalently linked with either G1P or G2P via a linker, as compared to the conventional HFB4 terminus. The effectiveness of this innovation is exemplified in Figures 4 and 5, where novel G3 variants, derived from the improved G3P as a parent, exhibit even greater PET degradation total activity, protein titer, and PET degradation specific activity. These pivotal metrics - PET degradation total activity, protein titer, and PET degradation specific activity - hold paramount importance in achieving efficient and cost-effective PET degradation. The present disclosure pertains to the development of PETase variants originating from the bacterium HR29 (Bhr-PETase), which have undergone deliberate engineering to elevate their PET degradation total activity, protein titer, and / or PET degradation specific activity. The exceptional performance exhibited by these Bhr-PETase variants underscores their substantial potential for further analysis and wide-ranging industrial applications. B. Definitions By "modification" herein is meant an amino acid substitution, insertion, and / or deletion in a polypeptide sequence or an alteration to a moiety chemically linked to a protein. For example, a modification may be an altered carbohydrate or PEG structure attached to a protein. By "amino acid modification" herein is meant an amino acid substitution, insertion, and / or deletion in a polypeptide sequence. For clarity, unless otherwise noted, the amino acid modification is always to an amino acid coded for by DNA, e.g. the 20 amino acids that have codons in DNA and RNA. By "amino acid substitution" or "substitution" herein is meant the replacement of an amino acid at a particular position in a parent polypeptide sequence with a different amino acid. In particular, in some embodiments, the substitution is to an amino acid that is not naturally occurring at the particular position, either not naturally occurring within the organism or in any organism. For example, the substitution V177I refers to a variant polypeptide, in this case a PETase, in which the valine (V) at position 177 is replaced with isoleucine (I). For clarity, a protein which has been engineered to change the nucleic acid coding sequence but not change the starting amino acid (for example exchanging CGG (encoding arginine) to CGA (still encoding arginine) to increase host organism expression levels) is not an “amino acid substitution”; that is, despite the creation of a new gene encoding the same protein, if the protein has the same amino acid at the particular position that it started with, it is not an amino acid substitution. By "amino acid insertion" or "insertion" as used herein is meant the addition of an amino acid sequence at a particular position in a parent polypeptide sequence. For example, -233E or 233E designates an insertion of glutamic acid after position 233 and before position 234. Additionally, - 233ADE or A233ADE designates an insertion of AlaAspGlu after position 233 and before position 234. By "amino acid deletion" or "deletion" as used herein is meant the removal of an amino acid sequence at a particular position in a parent polypeptide sequence. For example, F250- or F250#, F250() or F250del designates a deletion of glutamic acid at position 250. Additionally, FRS250- or FRS250# designates a deletion of the sequence PheArgSer that begins at position 250. By "parent polypeptide" as used herein is meant a starting polypeptide that is subsequently modified to generate a variant. The parent polypeptide may be a naturally occurring polypeptide, or a variant or engineered version of a naturally occurring polypeptide. Parent polypeptide may refer to the polypeptide itself, compositions that comprise the parent polypeptide, or the amino acid sequence that encodes it. In the present case, some embodiments utilize an exemplary variant Bhr- PETase (also called G3P Bhr-PETase; SEQ ID NO: 5; sequence shown in Figure 7) as the parent polypeptide. By "variant protein" or "protein variant", or "variant" as used herein is meant a protein that differs from that of a parent protein by virtue of at least one amino acid modification. Protein variant may refer to the protein itself, a composition comprising the protein, or the amino sequence that encodes it. Preferably, the protein variant has at least one amino acid modification compared to the parent protein, e.g. from about one to about seventy amino acid modifications, and preferably from about one to about five amino acid modifications compared to the parent. As described below, in some embodiments the parent polypeptide is a variant sequence, for example the exemplary variant Bhr-PETase designated “G3P” herein. As further discussed below, the protein variant sequence herein will preferably possess at least about 80, 81, 82, 83, 84, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% identity with a parent protein sequence, preferably at least about 90% identity, and preferably at least about 95, 98, or 99% identity. Variant protein can refer to the variant protein itself, compositions comprising the protein variant, or the DNA sequence that encodes it. Thus, by “variant PETase” herein is meant a novel PETase that has at least one amino acid modification in the amino acid sequence as compared to a parent PETase enzyme. Unless otherwise noted or as will be obvious from the context, the variant PETases of the invention generally are compared to the variant G3P sequence. Additionally, unless otherwise noted, the variant PETases of the invention are enzymatically active, that is, there is detectable PETase activity using the PETase assay described in Example 5. As used herein, "protein" herein is meant at least two covalently attached amino acids, which includes proteins, polypeptides, oligopeptides and peptides. The peptidyl group generally comprise naturally occurring amino acids and peptide bonds. In addition, polypeptides may include synthetic derivatization of one or more side chains or termini, glycosylation, PEGylation, circular permutation, cyclization, linkers to other molecules, fusion to proteins or protein domains, and addition of peptide tags or labels. By "residue" as used herein is meant a position in a protein and its associated amino acid identity. For example, Valine 177 (also referred to as Val177 or V177) is a residue at position 177 in the G3P parental enzyme. By "non-naturally occurring modification" as used herein is meant an amino acid modification that is not found in the parent (e.g. G3P) enzyme in nature. By "amino acid" and "amino acid identity" as used herein is meant one of the 20 naturally occurring amino acids that are coded for by DNA and RNA. By "position" as used herein is meant a location in the sequence of a protein. In general, the position number (which is more fully discussed below) is relative to the first amino acid of the mature PETase sequence, e.g. excluding the signal peptide. By “PETase” herein is meant a protein with PETase activity. By “PETase activity” herein is meant that in the absence of MHTase, the enzyme catalyzes the hydrolysis of PET to mono(hydroxyethyl)terephthalate (MHET) as the major product. In the presence of MHTase, which is the case of Example 5, MHETase will further convert MHET to terephthalic acid (TPA) and ethylene glycol (EG) as the major products of the enzymatic reaction. Enzymes having detectable PETase activity in the assay outlined below and in Example 5 are considered PETases herein. The PETase activity may be measured as PET degradation total activity and / or specific activity as described herein. By “identity” in reference to two sequences herein is meant that the same amino acid is at the same position considering the alignment. The degree of identity between an amino acid sequence of the present invention ("invention sequence") and the parent amino acid sequence referred to in the claims (e.g. for G3P, SEQ ID NO:5) is calculated as the number of exact matches in an alignment of the two sequences, divided by the length of the "invention sequence," or the length of the SEQ ID NO:5, whichever is the shortest. The result is expressed in percent identity as calculated below. For purposes of the present invention, the mature polypeptide disclosed in SEQ ID NO:5 is used to determine the corresponding amino acid residue in another PETase of the present invention. The amino acid sequence of another PETase is aligned with the mature polypeptide disclosed in SEQ ID NO:5, and based on the alignment, the amino acid position number corresponding to any amino acid residue in the mature polypeptide disclosed in SEQ ID NO:5 is determined using the Needleman- Wunsch algorithm (Needleman and Wunsch, 1970, J. Mol. Biol.48: 443-453) as implemented in the Needle program of the EMBOSS package (EMBOSS: The European Molecular Biology Open Software Suite, Rice et al., 2000, Trends Genet.16: 276-277), preferably version 5.0.0 or later. The parameters used are gap open penalty of 10, gap extension penalty of 0.5, and the EBLOSUM62 (EMBOSS version of BLOSUM62) substitution matrix. Identification of the corresponding amino acid residue in another PETase can be determined by an alignment of multiple polypeptide sequences using several computer programs including, but not limited to, MUSCLE (multiple sequence comparison by log-expectation; version 3.5 or later; Edgar, 2004, Nucleic Acids Research 32: 1792-1797), MAFFT (version 6.857 or later; Katoh and Kuma, 2002, Nucleic Acids Research 30: 3059-3066; Katoh et al. , 2005, Nucleic Acids Research 33: 511 -518; Katoh and Toh, 2007, Bioinformatics 23: 372-374; Katoh et al., 2009, Methods in Molecular Biology 537: 39-64; Katoh and Toh, 2010, Bioinformatics 26: 1899-1900), EMBOSS EMMA employing ClustalW (1.83 or later; Thompson et al., 1994, Nucleic Acids Research 22: 4673-4680), and EMBL-EBI employing Clustal Omega (Sievers and Higgins, 2014, Methods Mol Biol.2014;1079:105–16), using their respective default parameters. When the other enzyme has diverged from the polypeptide of SEQ ID NO:5 such that traditional sequence-based comparison fails to detect their relationship (Lindahl and Elofsson, 2000, J. Mol. Biol.295: 613-615), other pairwise sequence comparison algorithms can be used. Greater sensitivity in sequence-based searching can be attained using search programs that utilize probabilistic representations of polypeptide families (profiles) to search databases. For example, the PSI-BLAST program generates profiles through an iterative database search process and is capable of detecting remote homologs (Atschul et al., 1997, Nucleic Acids Res.25: 3389-3402). Even greater sensitivity can be achieved if the family or superfamily for the polypeptide has one or more representatives in the protein structure databases. Programs such as GenTHREADER (Jones, 1999, J. Mol. Biol.287: 797-815; McGuffin and Jones, 2003, Bioinformatics 19: 874-881) utilize information from a variety of sources (PSI-BLAST, secondary structure prediction, structural alignment profiles, and solvation potentials) as input to a neural network that predicts the structural fold for a query sequence. Similarly, the method of Gough et al., 2000, J. Mol. Biol.313: 903-919, can be used to align a sequence of unknown structure with the superfamily models present in the SCOP database. These alignments can in turn be used to generate homology models for the polypeptide, and such models can be assessed for accuracy using a variety of tools developed for that purpose. For proteins of known structure, several tools and resources are available for retrieving and generating structural alignments. For example the SCOP superfamilies of proteins have been structurally aligned, and those alignments are accessible and downloadable. Two or more protein structures can be aligned using a variety of algorithms such as the distance alignment matrix (Holm and Sander, 1998, Proteins 33: 88-96) or combinatorial extension (Shindyalov and Bourne, 1998, Protein Engineering 11 : 739-747), and implementation of these algorithms can additionally be utilized to query structure databases with a structure of interest in order to discover possible structural homologs (e.g., Holm and Park, 2000, Bioinformatics 16: 566-567). In describing the variants of the present invention, the nomenclature described below is adapted for ease of reference. The standardly accepted IUPAC single letter or three letter amino acid abbreviation is employed. For an amino acid substitution, the following nomenclature is used herein: Original amino acid, position, substituted amino acid. Accordingly, the substitution of valine at position 177 with isoleucine is designated as “Val177Ile” or “V177I”. Multiple mutations are separated by forward slash marks (“ / ”), e.g., “A174G / P213A”, representing substitutions at positions 174 and 213, respectively. Abbreviation 1 letter Amino acid name Abbreviation 1 letter Amino acid name Ala A Alanine Leu L Leucine Arg R Arginine Lys K Lysine Asn N Asparagine Met M Methionine Asp D Aspartic acid Phe F Phenylalanine Cys C Cysteine Pro P Proline Gln Q Glutamine Ser S Serine Glu E Glutamic acid Thr T Threonine Gly G Glycine Trp W Tryptophan His H Histidine Tyr Y Tyrosine Ile I Isoleucine Val V Valine By “isolated” in the context of a PETase herein is meant that the polypeptide is devoid of other proteins. In a particular embodiment the PETase of the invention is isolated. The term "isolated" as used herein refers to a polypeptide which is at least 20% pure, preferably at least 40% pure, more preferably at least 60% pure, even more preferably at least 80% pure, most preferably at least 90% pure, and even most preferably at least 95 to 98% pure, as determined by SDS-PAGE. In particular, it is preferred that the polypeptides are in "essentially pure form", i.e., that the polypeptide preparation is essentially free of other polypeptide material with which it is natively associated. This can be accomplished, for example, by preparing the polypeptide by means of well-known recombinant methods or by classical purification methods. By “recombinant enzyme” herein is meant that the enzyme is produced by recombinant techniques and that nucleic acid encoding the enzyme of the invention is operably linked to at least one exogeneous (e.g. not native to the parent PETase) sequence, including, for examples, promoters, terminators, signal sequences, etc., as are more fully outlined below. The term “nucleic acid construct” refers to a nucleic acid molecule, either single-stranded or double- stranded, which is isolated from a naturally occurring gene or is modified to contain segments of nucleic acids in a manner that would not otherwise exist in nature or which is synthetic, and which comprises one or more control sequences. The term “operably linked” refers to a configuration in which a control sequence is placed at an appropriate position relative to the coding sequence of a polynucleotide such that the control sequence directs expression of the coding sequence. As used herein, the term “about” means modifying, for example, lengths of nucleotide sequences, degrees of errors, dimensions, the quantity of an ingredient in a composition, concentrations, volumes, process temperature, process time, yields, flow rates, pressures, and like values, and ranges thereof, refers to variation in the numerical quantity that may occur, for example, through typical measuring and handling procedures used for making compounds, compositions, concentrates or use formulations; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of starting materials or ingredients used to carry out the methods; and like considerations. The term “about” also encompasses amounts that differ due to aging of, for example, a composition, formulation, or cell culture with a particular initial concentration or mixture, and amounts that differ due to mixing or processing a composition or formulation with a particular initial concentration or mixture. Whether modified by the term “about” the claims appended hereto include equivalents to these quantities. The term “about” further may refer to a range of values that are similar to the stated reference value. In certain embodiments, the term “about” refers to a range of values that fall within 10, 9, 8,7, 6, 5,4, 3, 2, 1 percent or less of the stated reference value. C. PETases of the Invention Accordingly, the present invention provides variant PETases with improved enzymatic activity and protein titer that can be used in a variety of applications, most notably in the degradation of plastics made from PET. In general, the variant PETases of the invention have modified, improved biochemical properties as compared to the variant Bhr-PETase, “G3P” (i.e. “Generation 3 Parent”), SEQ ID NO:5 herein, as shown in Figure 7. The biochemical properties of the variant PETases that can be improved herein include, but are not limited to, total activity, protein titer, and specific activity. The variant Bhr-PETases of the invention have one or more improved properties as compared to G3P. By “improved” herein is meant a desirable change of at least one biochemical property. “Improved function” can be measured as a percentage increase or decrease of a particular activity, or as a “fold” change, with increases of desirable properties (e.g. activity or thermostability). That is, a variant Bhr-PETase may have a 10% increase in thermostability or a 10% increase in PETase activity, as compared to G3P. In general, percentage changes are used to describe changes in biochemical activity of less than 100%, and fold-changes are used to describe changes in biochemical activity of greater than 100% (as compared to the parental enzyme, in many cases G3P). In the present invention, percentage changes (usually increases) of biochemical activity of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 98% and 99% can be accomplished. In the present invention, a “fold increase” (or decrease) is measured as compared to the starting or parent enzyme. For example, as shown in the Figure 4B, the variant L90Y / T157S / V170L has 1.89 fold increase in total activity on PET as compared to G3P: this is calculated by [(activity of variant) / (activity of parent)]. In many embodiments, the improvement is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme using a Bhr-PETase activity assay, under conditions that challenge the variant Bhr-PETase against the G3P enzyme. 1. Total Activity Increases The present invention provides variant Bhr-PETases that have total activity equal to or greater than the total activity of G3P (the variant Bhr-PETase of SEQ ID NO:5). The “total activity” herein may be determined by monitoring the production of TPA (terephthalic acid) during the PET depolymerization reaction at an elevated temperature such as 65°C, quantified using a colorimetric assay or HPLC as described in Example 5. Any improvement in total activity may be due to the improvement of thermoactivity, specific activity, and / or production of the variant PETase. In many embodiments, the variant Bhr-PETases have improved total activity that is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme using a Bhr-PETase activity assay, under conditions that challenge the variant Bhr-PETase against the G3P enzyme. (i) Thermoactivity Increases In one aspect, the variant Bhr-PETases may have increased thermoactivity. The “thermoactivity” herein may be determined by monitoring the production of TPA (terephthalic acid), MHET (mono(hydroxyethyl)terephthalate) and BHET (bis(2-hydroxyl) terephthalate during the PET depolymerization reaction at an elevated temperature such as 65°C, quantified in mg of equivalent TPA generated per h per mg of enzyme (mgTPAeq.h-1mgenzyme-1). Herein “Equivalent TPA” is calculated by a sum of TPA, MHET converted to TPA, BHET converted to TPA, and any other measurable oligomers converted to TPA. Thus, PETases that have increased activity per milligram of enzyme as compared to G3P (the variant Bhr-PETase of SEQ ID NO:5) may show an improved thermoactivity. In many embodiments, the variant Bhr-PETases have improved thermoactivity that is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme using a Bhr-PETase activity assay, under conditions that challenge the variant Bhr-PETase against the G3P enzyme. (ii) Specific Activity Increases In another aspect, the variant Bhr-PETases may have increased specific activity. The “specific activity” herein may be determined by monitoring the production of TPA (terephthalic acid), MHET (mono(hydroxyethyl)terephthalate) and BHET (bis(2-hydroxyl) terephthalate during the PET depolymerization reaction at the optimal operating temperature of Bhr-PETases, quantified in mg of equivalent TPA generated per h per mg of enzyme (mgTPAeq.h-1mgenzyme-1). Thus, PETases that have increased activity per milligram of enzyme as compared to G3P (the variant Bhr-PETase of SEQ ID NO:5) may show an improved specific activity. In many embodiments, the variant Bhr-PETases have improved specific activity that is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In some embodiments, the variant Bhr-PETases have increased equivalent TPA generated per h per mg of enzyme that is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme, under conditions that challenge the variant Bhr-PETase against the G3P enzyme. (iii) Production Increases In one aspect, the variant Bhr-PETases may have increased production. The “production” herein may be determined by monitoring the protein titer of Bhr-PETase in g / L. Thus, PETases that have increased quantity per liter of enzyme supernatant as compared to G3P (the variant Bhr-PETase of SEQ ID NO:5) may show an improved production. In many embodiments, the variant Bhr-PETases have improved production that is at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme using a Bhr-PETase production assay, under conditions that challenge the variant Bhr-PETase against the G3P enzyme. 2. Thermostability Additionally, as will be appreciated by those in the art, it can be desirable to run PET degradation at around the glass transition temperature. Amorphous PET domains will increase the mobility at around the glass transition temperature (around 67-72°C), making it more accessible for enzyme hydrolysis. At higher temperatures above the transition temperature, the PET substrate will re- crystalize over time, which is not favorable for PET degradation. Therefore, for example, about 65- 72°C may be considered an optimal temperature range for PET degradation. Accordingly, in many embodiments, the variant Bhr-PETases have improved thermostability. “Thermostability” in this context means that the variant enzymes are more stable than G3P (the variant Bhr-PETase of SEQ ID NO:5) under the same thermal challenge conditions, that is, the activity of the variant is higher than that of the G3P enzyme under identical conditions (generally using an assay as outlined herein). In one embodiment, the variant Bhr-PETases are more stable than the G3P enzyme when exposed to temperatures of about 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84 and / or 85°C for a period of time, for example ranging from about 0.5, 1, 2, 3, 4, 5, or 6 hour to about 5, 6, 7, 8, 9, 10 hours or longer, depending on the ultimate conditions for the use of the variant Bhr- PETase. In some embodiments, the variant Bhr-PETases are more stable than the G3P enzyme when exposed to temperatures preferably from about 65°C to 85°C for at least about 0.5 hour, preferably from about 65°C to 72°C for at least about 1 hour, preferably at least 65°C for at least about 1 hour, preferably at least 70°C for at least about 1.5 hour. Accordingly, in many embodiments, the variant Bhr-PETases are more thermostable than the G3P enzyme by at least 1.1 fold, 1.2 fold, 1.3 fold, 1.4 fold, 1.5 fold, 1.6 fold, 1.7 fold, 1.8 fold, 1.9 fold, 2 fold, 3 fold, 4 fold, 5 fold, 6 fold, 7 fold, 8 fold, 9 fold, or 10 fold or higher. In general, improvements are measured as compared to the G3P enzyme using a Bhr-PETase activity assay, under conditions that measure the variant Bhr-PETase or G3P enzyme activity with and without thermal treatment. 3. PETase Assays There are several PETase activity assays that can be used to determine activity, as generally outlined in Example 5 for PET film-based assay. PETase activity can also be monitored by BHET (Bis(2- Hydroxyethyl) terephthalate) or pNPB (p-Nitrophenyl Butyrate) based assays. In pNPB assay, surrogate substrate p-nitrophenylbutyrate may be hydrolyzed by PETase to p-nitrophenol and butyric acid. The release of p-nitrophenol directly correlates to PETase activity and can be determined spectrophotometrically at 405 nm, for example. 4. Bhr-PETases The present invention provides a number of specific variant Bhr-PETases with improved activity, production and / or specific activity for use in the degradation of PET. In some embodiments, the variant Bhr-PETase has one or more amino acid substitutions at a position (relative to G1P, SEQ ID NO:5) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258. In some embodiments, the variant Bhr- PETase has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid substitutions at a position (relative to G3P, SEQ ID NO:5) selected from the same group. In some embodiments, the variant Bhr-PETase has one more amino acid substitutions selected from the group consisting of V177I, V177T, V170I, V170L, T206D, A216T, R12E, R12F, R12S, R12T, D203A, D203C, D203E, D203G, D203L, D203S, D203Y, F92D, S212E, S212H, S212I, S212Q, S212T, N211Q, P213A, Q182D, Q182E, Q182S, T206S, A174G, A209E, A216E, A216I, A246E, A246N, A246Q, D249L, E173A, E173D, E173N, E173P, E173T, E173V, E173W, I217M, L90A, N204G, N254F, Q258K, R12L, R12M, R12Q, S181D, S181Q, S181T, T157D, T157E, T157L, T157Q, T157S, T160M, V177W, D203K, D203N, D203R, D203V, F92G, F92Q, P213N, E173R, H156N, L90F, L90Y, N204S, N253S, R255W, S181A, T157A, T157G, T176S, R118C, C257P, R89I, R89K, R89M, N214D, A215D, A215K, A215S, S248C, S248R, H256V, A14V, N87K, and D91N. In some embodiments, the variant Bhr-PETase has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid substitutions selected from the same group. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the arginine at position 12 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is R12E. In some embodiments, the amino acid substitution is R12F. In some embodiments, the amino acid substitution is R12L. In some embodiments, the amino acid substitution is R12M. In some embodiments, the amino acid substitution is R12Q. In some embodiments, the amino acid substitution is R12S. In some embodiments, the amino acid substitution is R12T. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 14 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A14V. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 87 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N87K. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the arginine at position 89 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is R89I. In some embodiments, the amino acid substitution is R89K. In some embodiments, the amino acid substitution is R89M. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the leucine at position 90 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is L90A. In some embodiments, the amino acid substitution is L90F. In some embodiments, the amino acid substitution is L90Y. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the aspartic acid at position 91 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, cysteine, glycine, proline, alanine, isoleucine, methionine, phenylalanine, tryptophan, valine, serine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is D91N. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the phenylalanine at position 92 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is F92D. In some embodiments, the amino acid substitution is F92G. In some embodiments, the amino acid substitution is F92Q. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the arginine at position 118 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing proline (due to steric effects). In some embodiments, the amino acid substitution is R118C. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the histidine at position 156 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is H156N. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the threonine at position 157 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 157 naturally occurring amino acids, namely serine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is T157D. In some embodiments, the amino acid substitution is T157E. In some embodiments, the amino acid substitution is T157L. In some embodiments, the amino acid substitution is T157Q. In some embodiments, the amino acid substitution is T157S. In some embodiments, the amino acid substitution is T157A. In some embodiments, the amino acid substitution is T157G. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the threonine at position 160 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is T160M. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the valine at position 170 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is V170I. In some embodiments, the amino acid substitution is V170L. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the glutamic acid at position 173 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation). In some embodiments, the amino acid substitution is E173A. In some embodiments, the amino acid substitution is E173D. In some embodiments, the amino acid substitution is E173N. In some embodiments, the amino acid substitution is E173P. In some embodiments, the amino acid substitution is E173T. In some embodiments, the amino acid substitution is E173V. In some embodiments, the amino acid substitution is E173W. In some embodiments, the amino acid substitution is E173R. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 174 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A174G. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the threonine at position 176 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is T176S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the valine at position 177 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is V177I. In some embodiments, the amino acid substitution is V177T. In some embodiments, the amino acid substitution is V177W. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the serine at position 181 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is S181D. In some embodiments, the amino acid substitution is S181Q. In some embodiments, the amino acid substitution is S181T. In some embodiments, the amino acid substitution is S181A. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the glutamine at position 182 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is Q182D. In some embodiments, the amino acid substitution is Q182E. In some embodiments, the amino acid substitution is Q182S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the aspartic acid at position 203 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing proline (due to steric effects). In some embodiments, the amino acid substitution is D203A. In some embodiments, the amino acid substitution is D203C. In some embodiments, the amino acid substitution is D203E. In some embodiments, the amino acid substitution is D203G. In some embodiments, the amino acid substitution is D203L. In some embodiments, the amino acid substitution is D203S. In some embodiments, the amino acid substitution is D203Y. In some embodiments, the amino acid substitution is D203K. In some embodiments, the amino acid substitution is D203N. In some embodiments, the amino acid substitution is D203R. In some embodiments, the amino acid substitution is D203V. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 204 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N204G. In some embodiments, the amino acid substitution is N204S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the threonine at position 206 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is T206D. In some embodiments, the amino acid substitution is T206S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 209 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A209E. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 211 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N211Q. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the serine at position 212 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is S212E. In some embodiments, the amino acid substitution is S212H. In some embodiments, the amino acid substitution is S212I. In some embodiments, the amino acid substitution is S212Q. In some embodiments, the amino acid substitution is S212T. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the proline at position 213 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation). In some embodiments, the amino acid substitution is P213A. In some embodiments, the amino acid substitution is P213N. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 214 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N214D. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 215 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A215D. In some embodiments, the amino acid substitution is A215K. In some embodiments, the amino acid substitution is A215S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 216 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A216E. In some embodiments, the amino acid substitution is A216I. In some embodiments, the amino acid substitution is A216T. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the isoleucine at position 217 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is I217M. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the alanine at position 246 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is A246E. In some embodiments, the amino acid substitution is A246N. In some embodiments, the amino acid substitution is A246Q. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the serine at position 248 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing proline (due to steric effects). In some embodiments, the amino acid substitution is S248C. In some embodiments, the amino acid substitution is S248R. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the aspartic acid at position 249 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is D249L. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 253 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N253S. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the asparagine at position 254 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is N254F. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the arginine at position 255 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is R255W. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the histidine at position 256 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is H256V. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the cysteine at position 257 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, glutamine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine. In some embodiments, the amino acid substitution is C257P. In some embodiments, the variant Bhr-PETase has an amino acid substitution of the glutamine at position 258 of SEQ ID NO:5. In some embodiments, the substitution is with any other of the 19 naturally occurring amino acids, namely serine, threonine, asparagine, lysine, arginine, histidine, glutamic acid, aspartic acid, cysteine, glycine, proline, alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, valine and tyrosine, with some embodiments not utilizing cysteine (due to possible disulfide formation) or proline (due to steric effects). In some embodiments, the amino acid substitution is Q258K. In some embodiments, the variant Bhr-PETase enzyme has one or more amino acid substitutions at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 of the positions of SEQ ID NO: 5 as described above. D. Nucleic Acids of the Invention The present invention additional provides nucleic acids encoding the variant Bhr-PETases of the invention. As will be appreciated by those in the art, due to the degeneracy of the genetic code, an extremely large number of nucleic acids may be made, all of which encode the variant Bhr-PETases of the present invention. Thus, having identified a particular amino acid sequence, those skilled in the art could make any number of different nucleic acids, by simply modifying the sequence of one or more codons in a way which does not change the amino acid sequence of the protein. Thus, providing the amino acid sequence allows the generation of a very large number of different nucleic acid sequences encoding the proteins. In some embodiments, specific variant Bhr-PETases are encoded by specific nucleic acid sequences, as are listed in SEQ ID NO 6. In some embodiments, specific variant Bhr-PETases are encoded by a nucleic acid sequence having at least about 80, 81, 82, 83, 84, 85, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% identity to SEQ ID NO 6. As is known in the art, the nucleic acids encoding the components of the invention can be incorporated into expression vectors as is known in the art, and depending on the host cells used to produce the heterodimeric antibodies of the invention. Generally, the nucleic acids are operably linked to any number of regulatory elements (promoters, origin of replication, selectable markers, ribosomal binding sites, inducers, etc.). The expression vectors can be extra-chromosomal or integrating vectors. The nucleic acids and / or expression vectors of the invention are then transformed into any number of different types of host cells as is well known in the art, including mammalian, bacterial, yeast, insect and / or fungal cells, with bacteria, yeast and fungi finding use in many embodiments. 1. Preparation of Variants The nucleic acids encoding the variant Bhr-PETases of the invention can be prepared using any mutagenesis procedure known in the art, such as site-directed mutagenesis and synthetic gene construction as are well known in the art. Synthetic gene construction entails in vitro synthesis of a designed polynucleotide molecule to encode a polypeptide of interest. Gene synthesis can be performed utilizing a number of techniques, such as the multiplex microchip-based technology described by Tian et al. (2004, Nature 432: 1050-1054) and similar technologies wherein oligonucleotides are synthesized and assembled upon photo-programmable microfluidic chips. A preferred technique is GenScript®. 2. Regulatory sequences The present invention also relates to nucleic acid constructs comprising a polynucleotide encoding a variant of the present invention operably linked to one or more control sequences that direct the expression of the coding sequence in a suitable host cell under conditions compatible with the control sequences. The polynucleotide may be manipulated in a variety of ways to provide for expression of a variant. Manipulation of the polynucleotide prior to its insertion into a vector may be desirable or necessary depending on the expression vector. The techniques for modifying polynucleotides utilizing recombinant DNA methods are well known in the art. The control sequence may be a promoter, a polynucleotide which is recognized by a host cell for expression of the polynucleotide. The promoter contains transcriptional control sequences that mediate the expression of the variant. The promoter may be any polynucleotide that shows transcriptional activity in the host cell including mutant, truncated, and hybrid promoters, and may be obtained from genes encoding extracellular or intracellular polypeptides either homologous or heterologous to the host cell. Promoters for bacteria, yeast and fungi are well known in the art. Exemplary operons for expression in lactic acid bacteria include S. thermophilus lactose operons or L. lactic lac ABCDFEGX operons, which have been successfully used to induce foreign gene expression in hosts (eg, Simons et al., 1993, J. Bact.175: 5186-5175; see Mollet et al., 1993, J. Bact.175: 4315-4324). Non-limiting additional examples of constitutive promoters for bacteria include lac promoter, trp promoter, tac promoter, T7 promoter, erm promoter, tip promoter, nit promoter, and Sp6 promoter. Exemplary promoters for yeasts include, but not limited to, AOX1 promoter, ADH promoter, PH05 promoter, gal10 promoter, PKG promoter and GAP promoter. Other useful promoters for yeast host cells are described by Romanoset al., 1992, Yeast 8: 423-488. Moreover, examples of useful promoters for fungi vectors include, but not limit to, Aspergillus niger GLA promoter, Aspergillus nidulans GPD promoter, those derived from Aspergillus nidulans glycolytic genes, such as the adh3 promoter (McKnight et al., EMBO J.4:2093-2099,1985). 3. Codon Optimization While the variant coding sequence of G3P Bhr-PETase is shown in SEQ ID NO:5, those of skill in the art will recognize that for heterologous expression, codon optimization can be done to increase expression in any particular host organism. Codon optimization can be employed with any of the variant Bhr-PETase polypeptides of the present invention, in order to optimize expression in the host cell employed. Such methods are well known in the art and described in, for example, WO 2007 / 142954. In heterologous expression systems, optimization steps can improve the ability of the host to produce the desired variant Bhr-PETase polypeptides. Protein expression is governed by a host of factors including those that affect transcription, mRNA processing, and stability and initiation of translation. The polynucleotide optimization steps can include steps to improve the ability of the host to produce the foreign protein as well as steps to assist the researcher in efficiently designing expression constructs. Optimization strategies can include, for example, the modification of translation initiation regions, alteration of mRNA structural elements, and the use of different codon biases. The following paragraphs discuss potential problems that may result in reduced heterologous protein expression, and techniques that may overcome these problems. In some embodiments, reduced heterologous protein expression results from a rare codon-induced translational pause. A rare codon-induced translational pause includes the presence of codons in the polynucleotide of interest that are rarely used in the host organism can have a negative effect on protein translation due to their scarcity in the available tRNA pool. One method of improving optimal translation in the host organism includes performing includes performing codon optimization which can result in rare host codons being modified in the synthetic polynucleotide sequence. In some embodiments, reduced heterologous protein expression results from by alternate translational initiation. Alternate translational initiation can include a synthetic polynucleotide sequence inadvertently containing motifs capable of functioning as a ribosome binding site (RBS). These sites can result in initiating translation of a truncated protein from a gene-internal site. One method of reducing the possibility of producing a truncated protein, which can be difficult to remove during purification, includes modifying putative internal RBS sequences from an optimized polynucleotide sequence. In some embodiments, reduced heterologous protein expression occurs through repeat-induced polymerase slippage. Repeat-induced polymerase slippage involves nucleotide sequence repeats that have been shown to cause slippage or stuttering of DNA polymerase which can result in frameshift mutations. Such repeats can also cause slippage of RNA polymerase. In an organism with a high G+C content bias, there can be a higher degree of repeats composed of G or C nucleotide repeats. Therefore, one method of reducing the possibility of inducing RNA polymerase slippage includes altering extended repeats of G or C nucleotides. In some embodiments, reduced heterologous protein expression occurs through interfering secondary structures. Secondary structures can sequester the RBS sequence or initiation codon and have been correlated to a reduction in protein expression. Stemloop structures can also be involved in transcriptional pausing and attenuation. An optimized polynucleotide sequence can contain minimal secondary structures in the RBS and gene coding regions of the nucleotide sequence to allow for improved transcription and translation. In some embodiments, restriction sites can affect heterologous protein expression. By modifying restriction sites that could interfere with subsequent sub-cloning of transcription units into host expression vectors a polynucleotide sequence can be optimized. Optimizing a DNA sequence can negatively or positively affect gene expression or protein production. For example, modifying a less-common codon with a more common codon may affect the half-life of the mRNA or alter its structure by introducing a secondary structure that interferes with translation of the message. It may therefore be necessary, in certain instances, to alter the optimized message. All or a portion of a gene can be optimized. In some embodiments, the desired modulation of expression is achieved by optimizing essentially the entire gene. In other embodiments, the desired modulation will be achieved by optimizing part but not all of the gene. The codon usage of any coding sequence can be adjusted to achieve a desired property, for example high levels of expression in a specific cell type. The starting point for such an optimization may be a coding sequence with 100% common codons, or a coding sequence which contains a mixture of common and non-common codons. Two or more candidate sequences that differ in their codon usage can be generated and tested to determine if they possess the desired property. Candidate sequences can be evaluated by using a computer to search for the presence of regulatory elements, such as silencers or enhancers, and to search for the presence of regions of coding sequence which could be converted into such regulatory elements by an alteration in codon usage. Additional criteria can include enrichment for particular nucleotides, e.g., A, C, G or U, codon bias for a particular amino acid, or the presence or absence of particular mRNA secondary or tertiary structure. Adjustment to the candidate sequence can be made based on a number of such criteria. Promising candidate sequences are constructed and then evaluated experimentally. Multiple candidates may be evaluated independently of each other, or the process can be iterative, either by using the most promising candidate as a new starting point, or by combining regions of two or more candidates to produce a novel hybrid. Further rounds of modification and evaluation can be included. Modifying the codon usage of a candidate sequence can result in the creation or destruction of either a positive or negative element. In general, a positive element refers to any element whose alteration or removal from the candidate sequence could result in a decrease in expression of the therapeutic protein, or whose creation could result in an increase in expression of a therapeutic protein. For example, a positive element can include an enhancer, a promoter, a downstream promoter element, a DNA binding site for a positive regulator (e.g., a transcriptional activator), or a sequence responsible for imparting or modifying an mRNA secondary or tertiary structure. A negative element refers to any element whose alteration or removal from the candidate sequence could result in an increase in expression of the therapeutic protein, or whose creation would result in a decrease in expression of the therapeutic protein. A negative element includes a silencer, a DNA binding site for a negative regulator (e.g., a transcriptional repressor), a transcriptional pause site, or a sequence that is responsible for imparting or modifying an mRNA secondary or tertiary structure. In general, a negative element arises more frequently than a positive element. Thus, any change in codon usage that results in an increase in protein expression is more likely to have arisen from the destruction of a negative element rather than the creation of a positive element. In addition, alteration of the candidate sequence is more likely to destroy a positive element than create a positive element. In some embodiments, a candidate sequence is chosen and modified so as to increase the production of a therapeutic protein. The candidate sequence can be modified, e.g., by sequentially altering the codons or by randomly altering the codons in the candidate sequence. A modified candidate sequence is then evaluated by determining the level of expression of the resulting therapeutic protein or by evaluating another parameter, e.g., a parameter correlated to the level of expression. A candidate sequence which produces an increased level of a therapeutic protein as compared to an unaltered candidate sequence is chosen. In some embodiments, one or a group of codons can be modified, e.g., without reference to protein or message structure and tested. Alternatively, one or more codons can be chosen on a message- level property, e.g., location in a region of predetermined, e.g., high or low GC content, location in a region having a structure such as an enhancer or silencer, location in a region that can be modified to introduce a structure such as an enhancer or silencer, location in a region having, or predicted to have, secondary or tertiary structure, e.g., intra-chain pairing, inter-chain pairing, location in a region lacking, or predicted to lack, secondary or tertiary structure, e.g., intra-chain or inter-chain pairing. A particular modified region is chosen if it produces the desired result. Methods which systematically generate candidate sequences are useful. For example, one or a group, e.g., a contiguous block of codons, at various positions of a synthetic nucleic acid sequence can be modified with common codons (or with non-common codons, if for example, the starting sequence has been optimized) and the resulting sequence evaluated. Candidates can be generated by optimizing (or de-optimizing) a given “window” of codons in the sequence to generate a first candidate, and then moving the window to a new position in the sequence, and optimizing (or de- optimizing) the codons in the new position under the window to provide a second candidate. Candidates can be evaluated by determining the level of expression they provide, or by evaluating another parameter, e.g., a parameter correlated to the level of expression. Some parameters can be evaluated by inspection or computationally, e.g., the possession or lack thereof of high or low GC content; a sequence element such as an enhancer or silencer; secondary or tertiary structure, e.g., intra-chain or inter-chain paring. In some embodiments, the optimized nucleic acid sequence can express the variant Bhr-PETase polypeptide of the invention, at a level which is at least about 110%, 150%, 200%, 500%, 1,000%, 5,000% or even 10,000% of that expressed by nucleic acid sequence that has not been optimized. Starting with the amino acid sequence of a variant Bhr-PETase, a candidate DNA sequence can be designed. During the design of the synthetic DNA sequence, the frequency of codon usage can be compared to the codon usage of the host expression organism and rare host codons can be modified in the synthetic sequence. Additionally, the synthetic candidate DNA sequence can be modified in order to remove undesirable enzyme restriction sites and add or alter any desired signal sequences, linkers or untranslated regions. The synthetic DNA sequence can be analyzed for the presence of secondary structure that may interfere with the translation process, such as G / C repeats and stem- loop structures. Before the candidate DNA sequence is synthesized, the optimized sequence design can be checked to verify that the sequence correctly encodes the desired amino acid sequence. Finally, the candidate DNA sequence can be synthesized using DNA synthesis techniques, such as those known in the art. In some embodiments, the general codon usage in a host organism, such as any of those described herein, can be utilized to optimize the expression of the heterologous polynucleotide sequence in the host organism. The percentage and distribution of codons that rarely would be considered as preferred for a particular amino acid in the host expression system can be evaluated. Values of 5% and 10% usage can be used as cutoff values for the determination of rare codons. 4. Host Cells and Production Strains In one aspect, the present disclosure relates to an expression vector comprising the nucleic acid encoding the variant Bhr-PETase described herein. In another aspect, the present disclosure also relates to a host cell comprising the expression vector. In some embodiments, the host cell is bacteria. In some embodiments, the host cell is yeast. In some embodiments, the host cell is fungi. In some embodiments, the host cell may be bacteria, including but not limited to E. coli, Bacillus. In some embodiments, the host cell may be yeast, including but not limited to Saccharomyces cerevisiae, Pichia. In some embodiments, the host cell may be fungi, including but not limited to A. niger, T. reseei, or Myceliophthora thermophila. The expression vector may be any of integration vectors which are to be integrated into genome or autonomously replicating plasmids in the selected host. In one embodiment, the vector can be stably maintained in the introduced cell, with the variant Bhr-PETase gene supported thereon in a fit state for expression. The expression vector may be selected to be suitable for the specific host cells to which the vector is introduced. Specific examples available for use include but not limit to pBR322, pACYC184, pUC18, pKK223-2, pHSG398 (Takara Bio Inc.), pTrcHis (Invitrogen Corporation) and pET11a (Stratagene Corporation) in the case where Escherichia coli is used as a host; pBBR122 (Mobiotech) and pBHR1 (Mobiotech) for the other gram-negative bacteria; pHW1520 (Mobiotech) and pHY300PLK (Takara Bio Inc.) for Bacillus; pSH19 (Herai et al., Proc. Natl. Acad. Sci., 101, 14031- 14035, 2004), pIJ702 (John Innes Centre), pIJ943 (John Innes Centre), pIJ8600 (John Innes Centre), pIJ602 (John Innes Centre), 1, pTip-vectors (Nakashima et al., Appli. Environ. Microbiol., 70, 5557- 5568, 2004), pTYM19 (Onaka et al., J. Antibiot., 56, 950-956, 2003) for actinomycetes; pPICZα and pPIC9 (Thermo Fisher Scientific) for Pichia, and pAO815 (Invitrogen Corporation), pAUR101 (Takara Bio Inc.), pAUR123 (Takara Bio Inc.) and pAUR316 (Takara Bio Inc.) for fungi. In another aspect, the present disclosure also relates to a method of expressing the variant Bhr- PETase in the host cell. In another aspect, the present disclosure also relates to a method of making the variant Bhr-PETase comprising culturing the host cell under conditions wherein said variant Bhr- PETase is produced, and recovering said variant Bhr-PETase. The culture of a transformed organism may be performed in the medium which can be a nutritive medium of the transformed host cell without affecting the transformation of the variant Bhr-PETase. Such a medium comprises an appropriate carbon source, nitrogen source, inorganic salt, natural organic nutrient and the like. As a carbon source, glucose, fructose, glycerol, sorbitol, organic acids can be used individually or in combination. The concentration of the carbon source is not particularly limited and may be 1 to 10 %. As a nitrogen source, ammonium, urea, ammonium sulfate, ammonium nitrate, ammonium acetate and the like can be used individually or in combination of two or more members thereof. As an inorganic salt, salts such as monopotassium phosphate, dipotassium phosphate, magnesium sulfate, manganese sulfate and ferrous sulfate can be used. In addition, as an organic nutrient source having growth-promoting effects of the bacteria to be used, peptone, meat extract, yeast extract, corn steep liquor and casamino acids can be used and furthermore, a small amount vitamins and nucleic acids may be contained in the medium. 5. PETase Formulations and Uses As will be appreciated by those in the art, the formulation of the variant Bhr-PETases of the invention depends on its end use and the associated conditions. Suitable formulations for the variant Bhr-PETases of the invention include liquid formulations, dried formulations (including spray dried formulations), powdered formulations, granular formulations, and pelleted formulations. Bhr- PETases can also be formulated as “embedded in PET particles” for natural degradation. In some embodiments, the enzyme composition (i.e., polypeptide compositions) of the present invention can be in any form suitable for use, such as, for example, a crude fermentation broth with or without cells removed, a cell lysate with or without cellular debris, a semi-purified or purified enzyme composition, or a host cell, as a source of the enzymes. In some embodiments, the enzyme composition may be a dry powder or granulate, a non-dusting granulate, a liquid, a stabilized liquid, or a stabilized protected enzyme. Liquid enzyme compositions may, for instance, be stabilized by adding stabilizers such as a sugar, a sugar alcohol or another polyol, and / or lactic acid or another organic acid according to established processes. In some embodiments, the dosage of the polypeptide composition of the invention and other conditions under which the composition is used may be determined on the basis of methods known in the art. The above compositions are suitable for use in PET biodegradation, PET biocycling, PET upcycling, and / or PET surface modification processes. In some embodiments, the above compositions are used to degrade pretreated PET. PET pretreatment may be performed before the enzymatic degradation step. Commonly used PET pretreatment can be broadly classified into a) mechanical pretreatment, b) thermo-mechanical pretreatment, and c) chemical pretreatment. The mechanical process may involve grinding of the PET film into particles less than about 500 µm post sieving. This process could be combined with immersing the PET film into liquid nitrogen mainly for ease of the process of grinding. The advantage of this type of mechanical pretreatment may be enzyme accessibility due to reduced particle size. In the thermo-mechanical degradation, the main-chain scission reactions may affect the stability of the cyclic oligomers. In the thermo-mechanical pretreatment, highly crystalline PET flakes may be amorphized at very high temperatures (> 260°C) using extruder equipped with melt pump and later micronized to particle size of less than 500µm. An example of a commercial method of pretreating PET is by using an extrusion cast process, namely molten polymer cast onto chilled rolls of PET to solidify. The thermo-mechanical pretreatment may lower the crystallinity as well as particle size of the industrial grade PET allowing accessibility of the enzymes to depolymerize it. In case of chemical pretreatment, ionic liquid, strong acid, base, solvents etc. can be used to reduce crystallinity or to change the surface structure of the PET to facilitate access of the enzymes to further depolymerize it to its monomers. The two significant stumbling blocks in recycling plastics irrespective of using chemical or biological method may be material variability and the costs associated with identifying and separating waste plastics into recognizable grade ranges. Different types and grades of plastics differ in densities and molecular weights. The advantage of knowing the properties of a particular plastic that is in the recycling process would make it easier to determine its value and durability when put into valuable second use applications. The process of sorting is however a major hindrance from the standpoint of resource utilization, time management, and cost effectiveness. Hence, when looking at biological mitigation to overcoming the roadblocks associated with differential plastic sorting, depolymerization of mixed plastics using robust enzymes that has broad substrate specificity becomes the utmost priority. Mixed plastic is a term that covers all non-bottle plastic packaging sourced from the domestic waste stream, and it includes rigid and flexible plastic items of various polymer types and colors that are typically found in the household waste bin. The mixed plastic refers to a mixture of different plastics. Various polymer types may refer to PET and / or analog of PET, PET-like or PET substitute derived biologically or chemically. Examples of analog of PET, PET-like or PET substitute include but are not limited to Polybutylene terephthalate (PBT), Polycabonate (PC), Polycaprolactone (PCL), Polyethylene Furanoate (PEF) and High Density Polyethylene (HDPE). Bhr- PETase alone or in conjunction with other accessory enzyme (s) can revolutionize the biological method of depolymerization of mixed plastics. The process of enzymatic depolymerization of mixed plastics as opposed to chemical methodologies may be environmentally safer and capable of retaining the market value of the second use applications. Such biological treatments can also be combined with mild chemical or thermomechanical pre-treatment to achieve higher depolymerization efficiencies. After PET pretreatment and enzymatic degradation, products may be recycled and generate other valuable chemicals. In one embodiment, TPA (terephthalic acid) is purified using an industry relevant process, and the process also may produce sodium sulphate, a chemical commonly used in the detergent, paper, and glass industries. In another embodiment, recycled TPA is used as the starting material to synthesize virgin PET. PET synthesized from recycled TPA may demonstrate similar properties, such as average molecular weight and intrinsic viscosity, as PET synthesized using petrochemical TPA. In one embodiment, bottles blown from recycled PET exhibits similar mechanical property and better lightness value than regular PET bottles. In some embodiments, the present invention provides a method of preparing enzyme cocktail comprising the variant Bhr-PETase as described herein with other PET degrading accessory enzymes and downstream MHETase to produce a PET degrading enzyme cocktail for the efficient turn-over of pretreated PET. EXAMPLES Example 1: Selection and Design of Novel Bhr-PETase Variant The amino acid sequence of the Bhr-PETase wildtype (SEQ ID NO: 1) is depicted in Figure 1. This wildtype functioned as the Generation 1 Parent (G1P) in our preceding patent application (Patent Application No: 2022074866). Variants identified in that patent, specifically G2P with the S27L mutation, demonstrated enhanced PET degradation activity and was consequently selected for further optimization. Moreover, we designed G3P by introducing a novel C-terminal domain into G2P. The G3P C-terminal incorporates 5 mutations when compared to the wild-type HFB4 (GenBank accession no. XP_006964739.1). The sequence alignments of Bhr-PETase wildtype (SEQ ID NO: 1), G2P (SEQ ID NO: 3), and G3P (SEQ ID NO: 5) are presented in Figure 2, illustrating the targeted evolutionary development of these variants. Example 2: Evaluation of the Protein Titer of Bhr-PETase G1P, G2P and G3P in Large Scale The gene sequences encoding Bhr-PETase G1P (SEQ ID NO: 2), G2P (SEQ ID NO: 4) and G3P (SEQ ID NO: 6) from Example 1 were cloned into a proprietary expression vector. This vector was subsequently transformed into a proprietary production host organism, which had been optimized for enhanced protein expression. The transformed host organisms were cultured in a fermentation medium that was tailored for the growth requirements of the specific host. Throughout the fermentation process, critical parameters such as temperature, pH, aeration, agitation, and feeding schedules were meticulously controlled to maximize enzyme production. The progress of the fermentation was monitored by measuring the biomass concentration, and periodic sampling was conducted to evaluate protein expression levels. Upon completion of the fermentation cycle, the culture was processed to separate the supernatant from the cell biomass. The protein concentration within the supernatant was then quantified using the standard Bradford assay, which involved the binding of Coomassie Brilliant Blue dye to protein molecules and resulted in a measurable color change proportional to the protein concentration. The resultant data from the Bradford assay provided a quantitative measure of the engineered Bhr- PETase variants' improved protein production over the wildtype. The data, as graphically depicted in Figure 3, clearly showed highest protein titers in the supernatant for G3P, reflecting either enhanced expression or greater stability under the fermentation conditions employed. These increased protein titers not only indicated a potential for more efficacious PET degradation by G3P but also suggested a reduction in enzyme production costs for industrial-scale applications. Therefore, the comparative data substantiated G3P's advantages over the wildtype Bhr-PETase, underlining its value in environmentally sustainable PET recycling solutions. Example 3: Design and Construction of Bhr-PETase G3 Variant Collections To enhance the PET-degrading efficacy, protein titer, and specific activity of Bhr-PETase, diverse variant libraries were designed based on in-depth sequence and structural analysis. These libraries encompassed variants with modifications ranging from single to multiple amino acid substitutions. The parent for these libraries was the Bhr-PETase Generation 3 Parent (G3P), which contained the S27L amino acid modification and an added C-terminal PET binding domain for improved substrate affinity. These untagged libraries were primarily screened based on PET degradation capability. Concurrent screening for PET degradation, protein titer, and specific activity was facilitated through the generation of specialized libraries derived from a GFP-tagged G3P. The GFP tag allowed for rapid and straightforward quantification of protein production via fluorescence intensity. Mutagenesis and subsequent cloning of the mutated genes into suitable expression vectors were performed using established techniques. The resultant variants, whether GFP-tagged or not, were expressed in a host organism optimized for high-throughput screening. This approach streamlined the identification of variants with superior functional enhancements, based on activity and / or protein titer measurements enabled by the GFP tagging. Example 4: HTP Preparation of Bhr-PETase G3 Variants in Microtiter Plates Recombinant host strains containing Bhr-PETase variant genes were cultured from single colonies in 24-well microtiter plates containing a specific growth medium. Cultures were incubated overnight at 30°C with 200 rpm shaking and maintained at 85% relative humidity. These primary cultures were then diluted and inoculated into fresh plates with identical media. The cultures underwent further incubation under the same conditions and were induced periodically with an inducer compound over a span of up to 120 hours to maximize variant expression. Culture supernatants were subsequently decanted into round-bottom plates for storage at -20°C, preserving protein integrity prior to analysis via various assays. Example 5: HTP PET Film Assay for Evaluating PET Degradation Total Activity of All Bhr-PETase G3 Variants Amorphous PET film (0.25 mm thickness, Catalog # ES301445) was procured from Goodfellow. The film was cut into 1 x 30 cm strips with a paper trimmer and further reduced to approximately 1 x 0.25 cm strips. These strips were then ground into a fine powder using a mechanical grinder. In preparation for the assay, a resin loader accurately dispensed approximately 10-12 mg of PET powder into each well of a 96-well Costar deep well plate. To each well containing PET powder, 1.4 mL of 0.1 M sodium phosphate buffer (pH 8.0) was added. This was followed by the addition of 100 µL of the enzyme solution to the wells, after which the plates were sealed to minimize evaporation. The enzyme-PET mixture was incubated at 65°C for 72 hours to facilitate the enzymatic degradation of the PET. For other set of experiments, 300-700 µL of enzyme solution and 1200-800 µL of 0.4 M Tris-HCl buffer (pH 9.0) were added in each well containing PET powder (total volume of solution is 1.5 mL, the final concentration of Tris-HCl: 0.32-0.21 M). The plates were sealed to minimize evaporation. The enzyme-PET mixture was incubated at 65°C for 20-24 hours to facilitate the enzymatic degradation of the PET. After incubation, the plates were centrifuged at 4,000 rpm for 2 minutes to sediment any undigested PET. A 180 µL sample of the clear supernatant was transferred into a new Costar round bottom plate, to which 20 µL of an in-house prepared Is-MHETase enzyme solution was added. This new mixture was incubated at 50°C for 30 minutes to ensure the further degradation of any PET breakdown products. Post-secondary incubation, the plates were again centrifuged at 4,000 rpm for 2 minutes. The supernatant was diluted with sodium phosphate buffer (pH 7.2) to a concentration within the linear range of the detection assay. To this dilution, 50 µL of 10 mM EDTA and 50 µL of 10 mM FeSO4 were introduced. The reaction plates were then incubated in the dark for 10 minutes to mitigate the effects of light-sensitive components. A final centrifugation step at 4,000 rpm for 2 minutes preceded the transfer of 200 µL of the reaction mixture to a black clear-bottom fluorometric plate for fluorescence measurement. After a 10-minute stabilization period, endpoint fluorescence was recorded using an excitation wavelength of 328 nm and an emission wavelength of 421 nm, which are the specific parameters for TPA (Terephthalic Acid) detection. The results, illustrating the improved total activity of all variants in comparison to their parent enzyme (G3P), are documented in Figures 4 and 5. Example 6: High-Throughput Fluorescence Assay for Evaluating Protein Titer and PET Degradation Specific Activity of GFP-tagged Bhr-PETase G3 Variants The enzyme culture supernatants, prepared as detailed in Example 4, underwent fluorescence-based analysis for GFP-tagged variants. A plate reader was employed to measure fluorescence intensities at the characteristic excitation and emission wavelengths of GFP, with GFP-only controls included to correct for background fluorescence. Quantitative assessments of protein production levels for GFP-tagged variants were summarized in Figures 5, showcasing the relative increase in protein production compared to the GFP-tagged Bhr- PETase G3P. All variants were also subjected to PET degradation activity assessment as outlined in Example 5. The specific activity of each GFP-tagged variant was calculated by normalizing their PET degradation activity to the protein titer obtained from the fluorescence assay. Figures 5 collates and presents the data for GFP-tagged variants, highlighting variants that show enhanced PET degradation activity, protein titer and specific activity in comparison to their parent enzyme (GFP-tagged G3P). Example 7: Large scale PET Film Assay to Assess the Impact of Engineered G3P C- Terminal The experiment was conducted in 250 mL glass bottles. Amorphous PET film (Catalog # ES301445) with a thickness of 0.25 mm was procured from Goodfellow. The PET film was initially cut into strips measuring 1 x 30 cm using a paper trimmer. Subsequently, these strips were further cut into approximately 1 x 0.25 cm segments. The PET film strips were then finely ground into a powder using a mechanical grinder. PET powder loading ranging from 2 to 10 g / L was prepared in 0.1M sodium phosphate buffer with a pH of 8.0, reaching a final volume of 50 mL. Various doses of normalized proteins were employed for evaluation under conditions of 65°C with continuous shaking at 200 rpm. The reactions were allowed to progress for durations ranging from 6 to 144 hours. At different time points, samples were collected from the bottles, and the reactions were analyzed through High-Performance Liquid Chromatography (HPLC) to determine the quantity of Terephthalic Acid (TPA) generated. For HPLC analysis, a Zorbax Eclipse Plus C18 column (Rapid Resolution HD, 2.1 x 50 mm, 1.8-Micron) with part number 959757-902 was utilized, along with a guard column identified by part number 82175-901. The HPLC method was configured with a flow rate of 0.6 mL / minute and a column temperature set to 35°C. A gradient method was employed to detect Terephthalic Acid (TPA), with mobile phase 1 consisting of water with 0.1% trifluoroacetic acid and mobile phase 2 comprising Acetonitrile with 0.1% trifluoroacetic acid. The results of the PET assay are summarized in Figure 8. The engineered G3P C-terminal demonstrated an enhanced TPA %Conversion when covalently linked with G1P or G2P via a linker. These results further suggest that the engineered C-terminal exhibits more efficient PET degradation capabilities compared to the wild-type HFB4.

Claims

CLAIMS 1. A composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises a C-terminus having at least 96% identity to SEQ ID NO:7 and has PETase activity.

2. The composition according to claim 1, wherein said variant Bhr-PETase comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258.

3. The composition according to claim 1 or 2, wherein said variant Bhr-PETase has at least 85% identity to SEQ ID NO:5 and has PETase activity.

4. A composition comprising a variant Bhr-PETase as compared to SEQ ID NO:5, wherein said variant comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 177, 170, 206, 216, 12, 14, 87, 89, 90, 91, 92, 118, 156, 157, 160, 173, 174, 176, 181, 182, 203, 204, 209, 211, 212, 213, 214, 215, 217, 246, 248, 249, 253, 254, 255, 256, 257, and 258, wherein said variant Bhr-PETase has at least 85% identity to SEQ ID NO:5 and has PETase activity.

5. The composition according to any one of the preceding claims, wherein said variant Bhr-PETase has at least 95% identity to SEQ ID NO:5 and has PETase activity.

6. The composition according to any one of the preceding claims, wherein said variant Bhr-PETase comprises at least one amino acid substitution compared to SEQ ID NO: 5 at an amino acid position(s) selected from the group consisting of 89, 91, 118, 176, 214, 215, 248, 256, and 257.

7. The composition according to any one of the preceding claims, wherein said variant Bhr-PETase comprises at least one amino acid substitution compared to SEQ ID NO: 5 selected from the group consisting of V177I, V177T, V170I, V170L, T206D, A216T, R12E, R12F, R12S, R12T, D203A, D203C, D203E, D203G, D203L, D203S, D203Y, F92D, S212E, S212H, S212I, S212Q, S212T, N211Q, P213A, Q182D, Q182E, Q182S, T206S, A174G, A209E, A216E, A216I, A246E, A246N, A246Q, D249L, E173A, E173D, E173N, E173P, E173T, E173V, E173W, I217M, L90A, N204G, N254F, Q258K, R12L, R12M, R12Q, S181D, S181Q, S181T, T157D, T157E, T157L, T157Q, T157S, T160M, V177W, D203K, D203N, D203R, D203V, F92G, F92Q, P213N, E173R, H156N, L90F, L90Y, N204S, N253S, R255W, S181A,T157A, T157G, T176S, R118C, C257P, R89I, R89K, R89M, N214D, A215D, A215K, A215S, S248C, S248R, H256V, A14V, N87K, and D91N.

8. The composition according to claim 7, wherein said amino acid substitution is selected from the group consisting of T176S, R118C, C257P, R89I, R89K, R89M, N214D, A215D, A215K, A215S, S248C, S248R, H256V, and D91N.

9. The composition according to any one of the preceding claims, wherein said variant Bhr-PETase enzyme has one or more amino acid substitutions at one of said positions, two of said positions, three of said positions, four of said positions, five of said positions, six of said positions, seven of said positions, eight of said positions, nine of said positions, ten of said positions, eleven of said positions, twelve of said positions, thirteen of said positions, fourteen of said positions, fifteen of said positions, sixteen of said positions, seventeen of said positions, eighteen of said positions, nineteen of said positions or twenty of said positions.

10. The composition according to any one of the preceding claims, wherein said variant Bhr-PETase comprises a set of amino acid substitutions selected from the group consisting of A174G / P213A, D203K / A215S, E173W / Q182E, L90Y / A174G, L90Y / T176S, R118C / Q182D, R12E / D203R, R12F / T157Q, R12Q / D203L, R12Q / T176S, R12T / R89K, R89I / T160M, R89K / L90F, T176S / N211Q, V170I / Q182E, A174G / D203A / A216E, A174G / P213N / N214D, D203G / A216E / I217M, E173N / S181D / S212E, F92G / E173V / T206D, F92G / T157Q / V170I, L90F / N211Q / S212T, R12E / T157L / A215S, R12E / T157L / A246E, R12Q / T157L / A174G, S181A / Q182S / D203S, T176S / D203A / A216I, V170I / A215D / A216T, V170I / E173T / S181D, A174G / T176S / D203G / A215D, L90F / E173R / A174G / V177W, L90F / F92Q / E173D / P213A, L90Y / A174G / T176S / A216E, L90Y / T176S / V177I / D203E, R12E / V170I / V177T / S212H, R12M / V170L / A174G / S181D, R12Q / T157L / T176S / V177I, R12T / V170I / T176S / V177T, R89I / A174G / T176S / A215K, R89I / L90F / E173D / S181A, R89M / T157G / S181T / Q182E, T157G / V170I / S181T / S212Q, T157Q / V170I / S181D / S212H, V170I / T176S / V177T / A246E, L90F / F92G / V170I / T176S / V177T, L90Y / A174G / T176S / V177I / Q182E, L90Y / F92Q / N204G / N211Q / A215S, L90Y / T157Q / V170I / S181Q / Q182D, R12E / L90F / V177I / D203C / A216I, R12E / R89K / L90F / V170I / T176S, R12F / V170L / T176S / V177I / S181D, R89I / L90Y / H156N / T157L / V177I, T157Q / V170L / S181T / Q182D / D249L, V170I / S181Q / Q182E / D203Y / A215D, V170L / S181D / Q182E / S212H / A246E, L90Y / V170I / T176S / V177I / Q182D / A246E, R12E / E173R / S181T / T206D / S212E / A246N, R12F / L90F / F92G / E173V / S181T / Q182D, R12M / A174G / S181T / Q182D / T206D / S212H, R12T / V177T / D203V / A215D / A246N / S248C, T157E / V170L / V177I / Q182E / A215D / A246N, T157Q / V170L / T176S / V177T / A215D / A216T,V170I / T176S / V177T / S181D / D203K / S212E, V170L / A174G / T176S / Q182D / S212Q / A246E, F92G / T157L / V170I / T176S / S181Q / Q182E / S212H, L90F / F92D / V170L / T176S / D203S / T206D / S212H, L90Y / F92G / Q182S / N211Q / S212I / A216E / I217M, L90Y / H156N / T157L / T176S / N204G / T206S / A215D, L90Y / V170I / V177T / D203Y / S212E / A246E / S248C, R12F / V170L / V177I / S181D / Q182E / S212E / A246E, R12L / R89K / L90Y / V170I / V177I / S181Q / Q182D, R12T / R89K / L90F / V170L / T176S / S181Q / A216T, R12T / T157Q / V170I / A174G / T176S / A215D / A216T, F92G / T157E / A174G / T176S / V177W / S181D / A215D / A216T, R12F / T157E / T176S / V177I / S212E / A215D / A216T / A246Q, R12M / R89K / L90Y / V170L / T176S / V177I / T206D / S212H, R89I / L90Y / T176S / S181A / Q182S / N204S / P213A / N214D, E173N / Q182D / A246Q / N253S / N254F / R255W / H256V / C257P / Q258K, L90Y / F92G / T157G / V170I / T176S / V177I / D203A / S212Q / A246E, R12F / L90F / T157G / E173R / A174G / Q182E / D203N / A216T / A246Q, L90Y / T157S / V170L, R12S / L90F / T157L / V170I / S181T / Q182D / A216T / A246E / S248R, R12T / T157L / V170L / V177T / D203S / A215D, R12S / R89K / T157L / V170I / T176S / S181D / Q182D / D203G / A216T, R12S / R89K / L90Y / T176S / V177I / Q182D / D203A, R12T / R89K / V170I / V177T, R12E / L90Y / T157L / E173A / A215D / A216T / A246E, R12E / L90Y / V170I / E173T / Q182D / A215D / A246E, R12E / V170I / V177T / D203R, R12E / V170L / T176S / A215D, R12E / L90Y / V170I / A174G / V177I / S181D / A215D / A216T / A246E / S248R, R12E / V170L / D203R / A246E, V170L / V177T / A246E, R12T / L90Y / V170I / D203G, R89K / L90Y / V177I / S181D / D203G / A215D / A216T, R12E / A216T, R12E / E173T / Q182D, R12E / E173A / A174G / S181T / Q182D / A216T, R12E / L90F / F92G / E173A / S181D / D203R, R12S / V170L / T176S / S181D, R12E / T176S / D203R / A246E, L90Y / V170I / T176S / V177T / S181D / D203R / A246E / S248R, R12E / V177I / D203R, R12S / V170I / T176S / V177T / S181D / Q182D / A246E, L90Y / E173P / A174G / S181D / D203G, R12E / D203K / A246E, R12T / L90F / E173A / A174G / S181D / A216T / D249L, L90Y / V170I / T176S / V177I / S181D / Q182D / A246E / S248C, R12T / R89K / L90Y / T157A, V170I / T176S / V177T / D203R / A246E / S248R, R12T / L90Y / V170L / V177I / A216T, L90Y / V170I / V177T / A216T, L90Y / F92G / T157A / V170I / D203G / A216T / A246E / S248C, R12T / L90Y / V170L / T176S / V177T / D203R / A216T, F92G / V170I / V177I / S181D, R12E / L90Y / V170I / T176S / S181T / D203R / A216T / A246E, R12T / D203R / D249L, L90Y / V170L / T176S / V177I, L90Y / V170L / V177T / D203G / A216T / A246E, L90Y / A246E, F92G / T157L / E173T / S181T / Q182D / A246E / S248C, L90F / F92G / V170I / V177T / D203R / A216T, R12S / E173P / S181T / D203R / A215D / A216T / A246E, R12E / F92G / A215D / A216T / A246E / S248R,R12E / L90A / E173P / A174G / S181T / Q182D / A215D / A216T, L90Y / D249L, F92G / T157A / E173P / A174G / S181D / A216T, L90F / D203R / D249L, R12T / L90Y / E173P / A174G / A246E, R12E / V170I / A174G / Q182D / D203R / A215D / A216T, R12E / E173P / S181T / Q182D / A215D / A216T, R12S / L90Y / S181T / Q182D / D203R, R12E / V170L / D203R / A215D / A246E, R12T / L90Y / V170L / A215D, R12E / F92G / V170I / A174G / T176S / D203R / A216T, R12E / V170I / E173P / S181T / D203R, R12T / T157S / E173P / A174G / S181D / D203R / A246E / S248R, R12E / L90Y / V170L / A174G / S181T / Q182D, R12E / S181T / Q182D / D203R / A215D, R12E / T157L / A215D, R12S / V170I / V177T / D203R, R12T / L90Y / V170L / D203A, R12E / T176S / V177T / D203R / A215D, R12S / V170I / Q182D / A215D / A216T, R12T / L90Y / V170I / V177T, R12S / R89K / L90A / V170I / A174G / T176S / S181D / Q182D, R12E / V170L / S181D / A215D, R12T / T157E / V170L / T176S / S181T / D203R / A215D / A246E, R12E / L90Y / T157A / E173A / S181T / Q182D / A215D / A216T, R12E / N87K / R89K / V170I / T176S / V177I / D203R / A215D / A216T / D249L, R12E / V170I / T176S / V177I / S181D / Q182D, R12T / L90F / V170I / S181D, R12T / L90Y / V170L / T176S / V177T / D203R / A246E, R12E / F92G / T157E / E173A / A174G / S181T / Q182D, R12E / F92G / V170I / T176S / V177T / A215D / A216T / A246E, R12T / V170I / T176S / V177T / D203R, R12E / L90Y / E173P / A174G / S181T / Q182D, R12E / T157D, R89K / L90F / T157A, R12E / L90Y / T157L / V170L / T176S / V177T / S181D / Q182D / D203R / A246E, R12S / V170L / T176S / V177I, R12E / L90F / F92G / V170L / V177T / D203R / A216T, V170I / A174G / S181D / D203R / A246E / S248R, V170I / S181T / Q182D, R12E / T157E / T176S / Q182D / A215D / A216T, R12S / V170I / S181D / D203R / A215D / A216T, R12E / L90A / F92G / V170L / S181T, R12E / L90Y / T157E / D203K / A246E, R12E / R89K / L90F / T157L / E173A / A174G / S181T / Q182D / A216T / A246E, R12E / V170L / T176S / S181D / Q182D / A216T, R12E / R89K / L90Y / D203R, R12S / T157S / E173T / A174G / D203R / A215D, R12E / F92G / T176S / V177I, R12T / V170L / T176S / V177T / D203R / A216T, R89K / V170L / T176S / V177I / A215D, R12T / V170I / D203A / S212H, R12F / T157L / V170I / T176S / D203A / S212E, R12S / E173V / A174G / S181Q / Q182D, V170L / S181Q / Q182D, R12E / V170L / V177I / A246Q / S248R, T157Q / V170L / E173R / S181Q / Q182E / S212H, L90F / V170I / T176S / V177I / Q182D / A216T, T157Q / E173V / A174G / S181T / Q182D, R12T / L90F / F92G / V170I / A215D, E173R / A174G / Q182D, R12E / T157L / E173N / A174G / S181D / Q182D, L90F / V170L / T176S / V177T / A215D, R12L / F92G / T157E / V170L / S181T / Q182D / T206D / S212Q / A246Q, R12M / V170I / T176S / V177I / S212Q, V170I / T206D / S212Q, E173R / A174G / A209E / A215D / A246Q, L90F / V170I / Q182E / A215D, T157G / V170I / Q182E / D203V, R12S / R89K / L90F / E173P / Q182D / A246E, R12T / A174G / T176S, R12T / V170I, T157S / E173T / A174G / S181T / Q182E / A215D / A246N, R12F / L90Y,V170L / V177T / T206D / A215D, R12E / T157L / A246N, V170I / A174G / T176S / Q182E / T206D / A216T, D203L / S212H / D249L, L90Y / E173N / S181T / Q182E, R12T / Q182D / A215D / A216T, L90F / F92G / A246Q, L90A / T157S / V170L / V177I / T206D / S212Q, T157E / V170L / V177I / T206D / A209E, E173A / S181Q, E173N / S181D / D203G / A209E / A215D / A216T, E173V / A174G, R12S / L90Y / A246N / S248R, S212H / A246E, L90F / F92G / T157Q / V170I / V177W / A209E / A215D / A216T, R12S / V170L / A215D / A216T / A246E, R12T / L90A / E173P / A174G / S181D / Q182E, T157G / A209E / A215D / A246Q, T157S / V170I / V177T / S181T / Q182D / D203S / S212E / A246Q / S248C, T157D / V170L / A174G / V177W / T206D / S212H / A246E, F92G / T157Q / E173R / A174G / S181D / Q182D / A215D / A216T / S248R / D249L, R89M / L90F / T206D, R12F / R89K / V170I / A216T / S248C, R12E / T157Q / V170L / V177I / S212E / A216T / A246E, R12T / R89K / L90A / E173R / A174G / S181T / Q182D / A215D / A216T, R12F / A174G / Q182E / A209E / A216T, R12S / E173R / S181T / Q182D / T206D / A216T / A246E, R12T / L90A / D203Y / A209E / S212Q / A246Q, R12M / E173P / A174G / S181D / A209E / S212Q / A246E / S248R, R12T / R89K / L90Y / S212H / A215D / A246Q / S248C, R12T / R89K / L90A / A174G / T176S / S181T / Q182D / A215D / A246Q, R12M / S212H / S248C / D249L, R89K / L90F / A174G / S181D / S212E / A246E / S248C, R12L / R89K / L90Y / T157D / E173P / A174G / S181Q / Q182D / S212H, R12T / R89K / L90A / A215D / A216T / D249L, R12M / V170L / T206D / S212E / S248C / D249L, E173R / Q182D / A215D / A216T / S248R / D249L, R12L / A209E / A216T / A246Q / S248R, R89K / L90Y / T176S / V177W / D203Y / A216T, R12M / L90F / A174G / A246N / S248C, R12M / V170I / A174G / T176S / S181T / T206D / A246Q / S248C, A174G / D203G / A216T / S248C / D249L, R12E / L90A / E173R / S181Q / Q182E / A209E / S212Q / A246N / S248C, R12T / T157Q / V170L / T176S / V177T / T206D / A209E / A216T, R89K / L90Y / T206D / A209E / S212H / S248C, R12T / R89K / L90Y / A216T, R12S / V170L / A209E / A216T / A246E, R89K / T176S / V177I / S181Q / T206D / A209E / A215D / A216T / A246E, V170L / E173N / V177T / Q182D / T206D / A216T / A246Q, R12T / Q182E / D203V / A216T / A246E / S248C, R89K / L90Y / V170L / A174G / T176S / S181Q / S212E / A215D / A216T / A246E, R12T / L90A / T176S / S212E, A216T / S248C, A216T / A246Q / S248C, T157Q / V170L / T176S / Q182D / A209E / A216T / A246Q, R12E / T157Q / E173R / A174G / Q182E / D203L / N204G / S212Q / A246E / S248C, V170L / V177W / S181Q / Q182E / A209E / A216T / A246E, L90A / S212Q / A246E / S248C, L90F / S212E / A246E / S248C, R89K / L90Y / E173T / S181T / N204G / T206D / A215D / A246N / S248C, R12S / A216T / S248C, R12L / V170L / T206D / A209E / A215D / A216T / D249L, T157D / E173P / A174G / Q182E / T206D / A215D / A216T, R12F / E173R / S181T / A246E / S248C, R12F / T157D / V170L / A209E / A216T, T176S / V177W / A246N / S248C,R89K / L90A / E173W / A215D / A216T / A246E / S248C, L90Y / T157G / A174G / T176S / A216T / A246Q / S248C, S212E / A246E, S212E / A246E / S248C, V170L / A209E / A216T / D249L, R12L / V170L / V177T / D203K / S212H / S248C / D249L, R12T / V170L / T176S / V177T / A209E, R12T / L90Y / F92G / V170I / V177I / S212E / A246Q / S248C, R12E / R89K / L90A / V170I / V177I / T206D / A215D / A216T, E173T / S248C / D249L, L90Y / E173V / S181D / T206D / S212Q / A246Q, D203K / A246E, T157G / V170L / T206D / A209E, L90A / E173P / A174G / S181T, A174G / T176S / A246N / S248R, L90F / F92G / D203S, V170I / T176S / V177W, V170L / V177I / S181T / Q182D / T206D / A209E / A215D / A216T, R12M / L90F / F92G / V170I / S181T / Q182D / S212E, R12M / A14V / V170I / V177T / S212H / A246E / S248C, R12L / L90A / D91N / F92G / A215D / A216T, R12L / F92G / V170I / S181T / T206D / S212H, R12T / V170L / S181T / Q182D, T157A / D203V / A209E / A215D, T157G / E173R / A246E, T157L / V170I / V177I / S212H, V170I / T176S / V177I / Q182D / N204G / T206D, V170I / V177W / A209E / A216T, V177I / A215D / A216T, V177I / A216T, A215D / A246E, R89K / V170I / T176S / V177I / D203S, R12E / E173A / V177T / A215D / A216T, V170L / T176S / Q182D, T157L / E173A, R12T / E173A / A174G / S181T / Q182D, R12E / L90F / V170I / T176S / S181T / Q182D, R12E / T157E / V170I / A174G / T176S / Q182D, R12E / E173A / A174G / A216T / A246E, R12T / E173T / A174G / S181D / Q182D, R12E / A215D / A216T / A246E, R12T / R89K / L90Y / T157A / V170I / A174G / T176S, R12E / A174G / S181T / Q182D, R12S / V170L / A174G / S181D, V170I / Q182D, L90F / A215D / A216T, L90F / A215D / A246E, R12S / E173P / S181D, R12S / A215D / A216T / S248C, V170I / E173T / S181T / Q182D / D203G / A215D / A246E, R12T / R89K / L90F / V170I / S181D / Q182D / D249L, T157A / V170I, A174G / T176S / A246E, R89K / L90F / V170I / V177T, F92G / T157L / V170I / Q182D, V170L / V177T, L90Y / V170I / V177I / A215D / A216T, R89K / L90Y / T157S / A174G / S181T / Q182D, V170L / T176S / A215D, F92G / V170L, V170I / V177T, V170L / T176S / V177I / S181D / D249L, E173T / A174G / Q182D / D203G / A216T, E173P / S181T / D203R / A216T / A246E / S248C, T157A / V170L / V177T, R12S / A246E, T157L / Q182D / A216T / A246E, L90F / E173T / A216T, R12T / A174G / S181T / Q182D / A246E / S248R, T157S / V170L / V177I, R12S / L90Y / V170I / E173A / A174G / S181T / Q182D / S248C / D249L, R12T / R89K / L90Y / Q182D / A246E / S248C, R12E / F92G / V170L / V177T / A215D / S248C, R12T / L90A / A246E / S248C, R12S / A216T, R12T / S181D / Q182D / A216T / A246E, T157D / A174G / S181T / Q182D / A216T, R12T / S248C / D249L, E173P / A174G / S181T / Q182D, T157S / E173A / S181D / S248R / D249L, L90F / E173P / A174G / A216T, F92G / T176S / A216T, L90Y / E173A / A174G / S181T / Q182D / A216T, F92G / V170I / A174G / T176S / D203N / A215D / A216T / A246E, L90F / F92G / A246E / S248R, T176S / V177T / A215D / A246E, R12F / T157Q / V170I / D203G / S212Q / D249L, R89K / L90F / T176S / V177I, L90F / T157E / V170I / T176S / V177I / S212H, E173T / S181D / D203N,V170I / T176S / D203K, V170I / V177I / T206D / A215D, R12S / Q182E / D203S / A216T, T157Q / V170I / V177T / T206D / S212Q / D249L, T157D / T176S / V177T, E173P / S181D, R12M / T157S / V170L / T176S / V177T / S181D / Q182D, L90Y / E173R / Q182D / N204G / T206D / S212H, R89K / E173V / S181Q, L90F / F92G / V170I / S181Q / Q182D / T206D / A215D, S181T / Q182E / A216T, R12T / L90A / E173N / A209E, R89K / L90F / T157E / S181T, T206D / S212H / A246E, E173P / A174G, R12T / T157Q, E173R / A174G / Q182D / A216T / A246Q, T157Q / V170I / V177T / A246E, R12T / L90F / E173R / S181Q / Q182E / A209E, R12L / R89K / L90Y / V170L / T176S / V177I / N204G / A215D, R12T / R89K / L90Y / V170I, R89K / V170L / T176S, T157S / S212Q, V170L / A209E / S212E, R12T / R89K / T157G / D203N / S212E / A246E, E173R / A174G / Q182D / D203R / A215D / A216T / A246N / S248C, R12T / V170L / V177T / S181T / A216T, R12M / E173R / S181T / Q182E / S212Q / A216T, R12S / V170I / T206D / A209E / A216T / A246E, R12T / T157Q / V170I / E173N / S181T / Q182D / A215D / A216T / A246Q / S248C, R12T / V170L / V177T / A216T, R12L / T157E / V177I / Q182E / S212H / A246N, R12L / R89K / L90Y / V170I / V177I / D203R, R12M / T157E / T206D / S212E, V170I / E173P / S181D / Q182E / A216T, R12S / F92G / V170L / T176S / A209E / A215D / A216T, R12S / L90F / F92G / T157E / V170I / T206D / A246E, V170L / T176S / V177I / S181T / Q182D / D203A / S212E, F92G / V177W / A215D / A216T, V170I / T176S / S181Q / Q182E / T206D / S212Q, T157G / S212E, L90Y / V170I / T176S / N204G / A216T, T157L / V170I / V177T / S181D / S212E, F92G / V170I / V177T, E173N / T176S / S181T / Q182D / A246E, T157G / E173A / S212E / A246E, T157Q / V170I / T176S / T206D / A215D / A246N / S248C, and T157A / A174G / T176S / S181D / Q182D / A215D / A216T.

11. A nucleic acid encoding the variant Bhr-PETase enzyme of any one of the preceding claims.

12. An expression vector comprising the nucleic acid of claim 11.

13. A host cell comprising the expression vector of claim 12.

14. The host cell according to claim 13, wherein the cell is bacteria, yeast or fungi.

15. A method of making a variant Bhr-PETase enzyme comprising culturing the host cell of claim 13 or 14 under conditions wherein said variant Bhr-PETase enzyme is produced, and recovering said variant Bhr-PETase enzyme.

16. A method of degrading PET, comprising contacting the PET with the variant BhrPETase enzyme of any one of claims 1-10.

17. The method according to claim 16, wherein the method degrades the PET in a mixed plastics composition.

18. The method according to claim 17, wherein the plastics composition comprises analog of PET, PET-like or PET substitute derived biologically or chemically.

19. The method according to claim 17, wherein the plastics composition comprises at least one selected from the group consisting of Polybutylene terephthalate (PBT), Polycabonate (PC), Polycaprolactone (PCL), Polyethylene Furanoate (PEF), and High Density Polyethylene (HDPE).

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