Effects of NADH-preferring xylose reductase expression on ethanol production from xylose in xylose-metabolizing recombinant Saccharomyces cerevisiae

• Published in: Journal of biotechnology Vol. 158; no. 4; pp. 184 - 191
• Main Authors: Lee, Sung-Haeng, Kodaki, Tsutomu, Park, Yong-Cheol, Seo, Jin-Ho
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.04.2012
• Subjects: Aerobiosis; aldehyde dehydrogenase; Aldehyde Oxidoreductases - genetics; Aldehyde Oxidoreductases - metabolism; Aldehyde Reductase - genetics; Aldehyde Reductase - metabolism; commercialization; D-Xylulose Reductase - biosynthesis; D-Xylulose Reductase - genetics; D-Xylulose Reductase - metabolism; Ethanol; Ethanol - metabolism; ethanol production; Fermentation; Gene Expression; gene overexpression; genes; Genes, Fungal; lignocellulose; Metabolic Engineering - methods; mutants; Mutation - genetics; NAD - genetics; NAD - metabolism; NADH-preferable xylose reductase; NADP - genetics; NADP - metabolism; Phosphotransferases (Alcohol Group Acceptor) - genetics; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Pichia - enzymology; Pichia - genetics; Pichia - metabolism; Recombination, Genetic; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - biosynthesis; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Scheffersomyces stipitis; transaldolase; Transaldolase - genetics; Transaldolase - metabolism; xylitol; Xylitol - genetics; Xylitol - metabolism; Xylose; Xylose - genetics; Xylose - metabolism; Xylose; NADH-preferable xylose reductase; Ethanol; Saccharomyces cerevisiae
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2011.06.005

► Cofactor-imbalance is a problem in xylose metabolism by recombinant S. cerevisiae. ► NADH-preferable XR, NAD-dependent XDH and XK were overexpressed in S. cerevisiae. ► Balanced expression of xylose metabolic enzymes reduced a major byproduct, xylitol. ► TAL expression and ALD6 deletion enhanced ethanol production from xylose considerably. Efficient conversion of xylose to ethanol is an essential factor for commercialization of lignocellulosic ethanol. To minimize production of xylitol, a major by-product in xylose metabolism and concomitantly improve ethanol production, Saccharomyces cerevisiae D452-2 was engineered to overexpress NADH-preferable xylose reductase mutant (XRMUT) and NAD+-dependent xylitol dehydrogenase (XDH) from Pichia stipitis and endogenous xylulokinase (XK). In vitro enzyme assay confirmed the functional expression of XRMUT, XDH and XK in recombinant S. cerevisiae strains. The change of wild type XR to XRMUT along with XK overexpression led to reduction of xylitol accumulation in microaerobic culture. More modulation of the xylose metabolism including overexpression of XRMUT and transaldolase, and disruption of the chromosomal ALD6 gene encoding aldehyde dehydrogenase (SX6MUT) improved the performance of ethanol production from xylose remarkably. Finally, oxygen-limited fermentation of S. cerevisiae SX6MUT resulted in 0.64gl−1h−1 xylose consumption rate, 0.25gl−1h−1 ethanol productivity and 39% ethanol yield based on the xylose consumed, which were 1.8, 4.2 and 2.2 times higher than the corresponding values of recombinant S. cerevisiae expressing XRMUT, XDH and XK only.