Allulose epimerase variant, method for producing same, and method for producing allulose using same
A technology of epimerase and psicose, applied in the field of D-psicose 3-epimerase, can solve the problems of poor thermal stability, low conversion rate, unsuitable for industrialization, etc. The effect of preventing pollution, high conversion activity and reducing production cost
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Embodiment 1
[0035] Example 1: Searching for amino acid substitution positions that improve the conversion rate and thermostability of D-psicose 3-epimerase
[0036] To improve the fructose-to-psicose conversion rate and thermostability of D-psicose 3-epimerase derived from Flavonifractor plautii, amino acid substitution positions were selected based on protein structure prediction. D-psicose 3-epimerase (or D-psicose 3 -epimerase). The D-psicose 3-epimerase derived from Flavonifractor plautii consists of the amino acid sequence shown in SEQ ID NO: 1, and has the maximum activity of converting fructose into psicose under neutral pH conditions , and it is possible to mass-produce psicose from fructose with high yield in a short period of time, but there is a problem in that when the enzyme reaction is performed under high temperature conditions to prevent contamination and the like, the activity rapidly decreases. In order to improve the conversion rate and thermal stability of fructose t...
Embodiment 2
[0037] Example 2: Preparation of recombinant vectors and recombinant strains overexpressing D-psicose 3-epimerase derived from Flavonifractor plautii
[0038] Based on the wild-type polynucleotide of the psicose epimerase derived from Flavonifractor plautii, nucleotides encoding five enzyme variants (I21C, A82R, L133D, G216S and A276R) were generated using overlap extension polymerase chain reaction. A polynucleotide fragment of an amino acid sequence.
[0039] First, a PCR reaction was performed using the primers shown in Table 1 below to prepare a gene encoding a psicose epimerase variant derived from Flavonifractorplautii. Specifically, 1 pM of the oligonucleotides in Table 1 was used as primers, and 100 ng of the wild-type polynucleotide (SEQ ID NO: 7) derived from the psicose epimerase variant of Flavonifractor plautii was used as a template. These two were mixed into a reaction solution to which 100 μM of deoxynucleoside triphosphate (dATP, dCTP, dGTP, dTTP) was added. ...
Embodiment 3
[0048] Example 3: Expression and purification of D-psicose 3-epimerase variants derived from Flavonifractor plautii
[0049] 1 ml of recombinant E. coli prepared in Example 2 was inoculated into a 1 L shake flask containing 150 ml of a protein expression medium having the composition of the following Table 3 (based on 1 L medium), and was incubated at 32° C. in a shaking incubator. Incubate for 24 hours while maintaining shaking conditions at 32° C. and 140 rpm. 1% lactose was included in the medium to induce overexpression of psicose epimerase variants.
[0050] table 3
[0051] Medium composition quantity Medium composition quantity glycerin 9.0% by weight MgSO 4
[0052] Then, overexpressed psicose epimerase variants were isolated by the following method. First, the culture solution of recombinant E. coli was centrifuged at 4100×g and 4° C. for about 15 minutes to remove the supernatant, and cells of the recombinant E. coli strain were recovered...
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