Improvement of d‐lactic acid productivity by introducing Escherichia coli acetyl‐CoA synthesis pathway in engineered Saccharomyces cerevisiae

Abstract

AbstractBACKGROUNDd‐Lactic acid (d‐LA) is gaining increased attention as it can be applied in the food, pharmaceutical, cosmetic, polylactic acid and textile industries. Acid‐tolerant Saccharomyces cerevisiae is often engineered to produce organic acids. For the pyruvate decarboxylases (PDCs) or alcohol dehydrogenase 1 (ADH1) disrupted strains, the productivity of d‐LA significantly decreases due to the accumulation of acetaldehyde and acetic acid. To overcome the problem, Escherichia coli acetylating acetaldehyde dehydrogenase (A‐ALD) enzyme genes (MHPF and EUTE) (EC 1.2.1.10) were integrated into the d‐LA producing strain YIP‐A15G12 strain (CGMCC2.5803). The function of these genes is to directly convert acetaldehyde into acetyl‐CoA without energy consumption. This strain was integrated with Escherichia coli d‐lactate dehydrogenase and Issatchenkia orientalis glycosylphosphatidylinositol‐anchored protein IoGas1gene and several attenuated key pathway genes, including PDC1, PDC6, ADH1, ADH5, JEN1 (a monocarboxylate transporter), d‐lactate dehydrogenase 1 (DLD1), l‐lactate cytochrome c oxidoreductase (CYB2) and glycerol‐3‐phosphate dehydrogenases (GPD1, GPD2).RESULTSThe strain expressions of the A‐ALD enzymes effectively complemented the attenuated acetaldehyde dehydrogenase (ALD) acetyl‐CoA synthetase (ACS) pathway and significantly improved the levels of acetyl‐CoA and the productivity of d‐LA. Finally, the resulting strainYIP‐m‐ald6 (CGMCC2.5826) produced 86.9 g L–1 d‐LA with a yield of 0.77 g g–1 glucose and a volumetric productivity of 1.77 g L–1 h–1 at pH 3.58 under fed‐batch fermentation conditions.CONCLUSIONIntroducing the E. coli acetyl‐CoA synthesis pathway into the yeast strain can significantly enhance the growth of the strain and improve the d‐LA productivity, as a benefit for d‐LA production in industry. © 2021 Society of Chemical Industry (SCI).