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Acetyl-coa producing enzymes in yeast

a technology of acetylcoa and producing enzymes, which is applied in the direction of biofuels, microorganisms, peptides, etc., can solve the problems of reducing the overall yield of the product on carbon, reducing the production efficiency of pdh by-pass in yeast, and unable to achieve maximum theoretical yield, etc., to achieve the effect of increasing the production of cytosolic acetyl-coa

Inactive Publication Date: 2010-09-30
DSM IP ASSETS BV
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AI Technical Summary

Benefits of technology

[0012]The present inventors have now identified alternative metabolic routes for increasing the production of cytosolic acetyl-CoA in yeast which can overcome the problems of the PDH by-pass.

Problems solved by technology

However, the PDH by-pass in yeast is not optimal with respect to the energy balance, as can be seen from the overall reaction stoichiometry: 2 moles of ATP are needed per acetyl-CoA synthesized via the PDH-bypass since in the acetyl-CoA synthetase reaction ATP is hydrolyzed to AMP.
The additional ATP requirement of the PDH by-pass can present a problem for synthesizing the product of interest from cytosolic acetyl-CoA precursor, as more carbon source needs to be diverted for ATP generation, via e.g. oxidative phosphorylation and / or substrate phosphorylation (e.g. glycolysis), thereby lowering the overall yield of the product on carbon.
However, when the PDH by-pass is used in combination with butanol biosynthesis, this maximal theoretical yield cannot be achieved due to energy imbalance: whereas 2 moles of ATP are generated per mole of glucose converted in glycolysis, a total of 4 moles (2 times 2 mole) of ATP are needed in the PDH by-pass to form 2 moles of acetyl-CoA, which are converted to 1 mole of butanol.
Thus, there is a net shortage of ATP if the PDH by-pass were used to synthesize 1 mole of 1-butanol from 1 mole of glucose.
These processes have the disadvantage that they are based on the use of petrochemical derivates, are generally expensive, and are not environmentally friendly.
An important disadvantage of the ABE process, however, is that it results in a mixture of acetone, 1-butanol and ethanol.
Moreover, the use of bacteria requires sterile process conditions and generally renders the process susceptible to bacteriophage infection.

Method used

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  • Acetyl-coa producing enzymes in yeast

Examples

Experimental program
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Effect test

example 1

Construction of Delta acs2 Strain

[0113]The S. cerevisiae acs2 deleted strain (acs2Δ strain) was produced by first performing a PCR on plasmid pUG6 (Güldener et al., 1996, supra) with the following oligonucleotides:

5′acs2::Kanlox5′-tacacaaacagaatacaggaaagtaaatcaatacaataataaaacagctgaagcttcgtacgc-3′3′acs2::Kanlox5′-tctcattacgaaatttttctcatttaagttatttctttttttgaggcataggccactagtggatctg-3′.

[0114]The resulting 1.4 kb fragment, containing the KanMX marker which confers resistance to G418, was used to transform S. cerevisiae CEN.PK113-3C (MATA trp1-289). After transformation the strain was plated on YPD (10 g I−1 yeast extract (BD Difco), 20 g I−1 peptone (BD Difco)), 10 g I−1 glucose) with 200 mg / ml Geneticin (G418). In resistant transformants, correct integration was verified by PCR using oligonucleotides:

5′ACS2:5′-gatattcggtagccgattcc-3′3′ACS2:5′-ccgtaaccttctcgtaatgc-3′ACS2internal:5′-cggattcgtcatcagcttca-3′KanA:5′-cgcacgtcaagactgtcaag-3′KanB:5′-tcgtatgtgaatgctggtcg-3′

[0115]The phenotype wa...

example 2

In Silico Identification of Putative Acetylating Acetaldehyde Dehydrogenases for Direct Conversion of Acetaldehyde to Acetyl-CoA

[0117]Enzymes described for the conversion of acetaldehyde to acetyl-CoA are the so-called acetylating acetaldehyde dehydrogenases (ACDH) (E.C. 1.2.1.10) catalysing the following reaction:

Acetaldehyde(AA)+NAD++CoAAcetyl-CoA+NADH+H+

[0118]From literature four types of proteins have been described that have this activity:

[0119]1) Bifunctional proteins that catalyze the reversible conversion of acetyl-CoA to acetaldehyde, and the subsequent reversible conversion of acetaldehyde to ethanol. An example of this type of proteins is the AdhE protein in E. coli (GenBank No: NP—415757). AdhE appears to be the evolutionary product of a gene fusion. The NH2-terminal region of the AdhE protein is highly homologous to aldehyde:NAD+ oxidoreductases, whereas the COOH-terminal region is homologous to a family of Fe2+ dependent ethanol:NAD+ oxidoreductases (Membrillo-Hernande...

example 3

Construction of Expression Plasmids and Complementation Test

[0125]To test whether acetylating acetaldehyde dehydrogenases (ACDH) could complement the deletion of ACS2 in S. cerevisiae, several genes coding for a (putative) ACDH were chosen from a variety of databases as described above.

[0126]To achieve optimal expression in yeast, the codon usage of all genes was adapted by codon pair optimization. These sequences were synthesized at Geneart AG (Regensburg, Germany).

[0127]The optimized sequences were cloned into the high copy yeast expression plasmid YEplac112PtdhTadh (SEQ ID NO:40; based on YEplac112 (2μ TRP1) (Gietz & Sugino [1988] Gene 74(2):527-34), allowing constitutive expression from the TDH3 promoter.

[0128]YEplac112PtdhTadh was made by cloning a KpnI-SacI fragment from p426GPD (Mumberg et al. [1995] Gene. 156(1):119-22), containing the TDH3 promoter and CYC1 terminator, into YEplac112 cut with KpnI-SacI. The resulting plasmid was cut with KpnI and SphI and the ends were made...

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Abstract

The present invention relates to a method of identifying a heterologous polypeptide having enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA in (the cytosol of) a yeast cell comprising: a) providing a mutated yeast cell comprising a deletion of at least one gene of the (PDH) by-pass, selected from the genes encoding the enzymes pyruvate decarboxylase (PDC), acetaldehyde dehydrogenase (ALD), and acetyl-CoA synthetase (ACS); b) transforming said mutated yeast cell with an expression vector comprising a heterologous nucleotide sequence encoding a candidate polypeptide having potential enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA; c) testing said recombinant mutated yeast cell for its ability to grow on minimal medium containing glucose as sole carbon source, and d) identifying said candidate polypeptide as a heterologous polypeptide having enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA in (the cytosol of) said yeast cell when growth of said cell is observed. The invention further relates to a method of producing a fermentation production such as butanol.

Description

FIELD OF THE INVENTION[0001]The present invention is in the field of metabolites production in yeast using heterologous expression systems. In particular, the present invention relates to the metabolic engineering of yeast strains capable of producing metabolites that require cytosolic acetyl-CoA as a precursor, such as butanol-producing yeast strains. The present invention relates to an assay system for identifying heterologous enzymes capable of converting pyruvate, acetaldehyde or acetate into cytosolic acetyl-CoA when expressed in the cytosol in yeast.BACKGROUND OF THE INVENTION[0002]Acetyl-coenzyme A (CoA) is an essential intermediate in numerous metabolic pathways, and is a key precursor in the synthesis of many industrial relevant compounds, such as fatty acids, carotenoids, isoprenoids, vitamins, amino acids, lipids, wax esters, (poly)saccharides polyhydroxyalkanoates, statins, polyketides and acetic esters (such as ethyl acetate and isoamyl acetate). In particular, acetyl-C...

Claims

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Application Information

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IPC IPC(8): C12Q1/68C12N15/63C12N1/19C12P7/16
CPCC07K14/33C12N9/001C12Q1/32Y02E50/10C12P7/16
Inventor MULLER, ULRIKE MARIAWU, LIANGRAAMSDONK, LOURINA MADELEINEWINKLER, AARON ADRIAAN
Owner DSM IP ASSETS BV
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