title: Decreased xylitol formation during xylose fermentation in Saccharomyces cerevisiae due to overexpression of water-forming NADH oxidase.
abstract: The recombinant xylose-fermenting Saccharomyces cerevisiae strain harboring xylose reductase (XR) and xylitol dehydrogenase (XDH) from Scheffersomyces stipitis requires NADPH and NAD(+), creates cofactor imbalance, and causes xylitol accumulation during growth on d-xylose. To solve this problem, noxE, encoding a water-forming NADH oxidase from Lactococcus lactis driven by the PGK1 promoter, was introduced into the xylose-utilizing yeast strain KAM-3X. A cofactor microcycle was set up between the utilization of NAD(+) by XDH and the formation of NAD(+) by water-forming NADH oxidase. Overexpression of noxE significantly decreased xylitol formation and increased final ethanol production during xylose fermentation. Under xylose fermentation conditions with an initial d-xylose concentration of 50 g/liter, the xylitol yields for of KAM-3X(pPGK1-noxE) and control strain KAM-3X were 0.058 g/g xylose and 0.191 g/g, respectively, which showed a 69.63% decrease owing to noxE overexpression; the ethanol yields were 0.294 g/g for KAM-3X(pPGK1-noxE) and 0.211 g/g for the control strain KAM-3X, which indicated a 39.33% increase due to noxE overexpression. At the same time, the glycerol yield also was reduced by 53.85% on account of the decrease in the NADH pool caused by overexpression of noxE.
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
authors.forename: Guo-Chang
authors.initials: GC
authors.lastname: Zhang
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Liu
authors.forename: Wen-Tao
authors.initials: WT
authors.lastname: Ding
mesh_terms: D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D015870:Gene Expression; D013294:Lactococcus lactis / Q000201:enzymology / Q000235:genetics; D060847:Metabolic Engineering / Q000379:methods; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism*; D014867:Water / Q000378:metabolism; D014993:Xylitol / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D014867:Water; D000431:Ethanol; D014994:Xylose; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D014993:Xylitol