title: Improving the ethanol yield by reducing glycerol formation using cofactor regulation in Saccharomyces cerevisiae.
abstract: To increase ethanol yield and decrease glycerol production in Saccharomyces cerevisiae, the strategies of direct cofactor-regulation were explored. During anaerobic batch fermentations, the yeast expressing Bacillus cereus gapN gene, encoding non-phosphorylating NADP(+)-dependent glyceraldehyde-3-phosphate dehydrognease, produced 73.8 g ethanol l(-1), corresponding to 96% of theoretical maximum yield compared to 92% for the wild type. The yeast expressing Escherichia coli frdA gene encoding the NAD(+)-dependent fumarate reductase, exhibited a 22% (relative to the amount of substrate consumed) increase in glycerol yield in medium containing 2 g fumarate l(-1). The yeast expressing mhpF gene, encoding acetylating NAD(+)-dependent acetaldehyde dehydrogenase, produced 74.5 g ethanol l(-1), corresponding to 97.4% of theoretical maximum yield while glycerol decreased by 40% when acetic acid was added before inoculation. This strain represents a promising alternative for ethanol production with lignocellulosic hydrolysates where acetate is available at significant amounts.
authors.affiliation: The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, People's Republic of China. zhangl@jiangnan.edu.cn
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Tang
authors.forename: Zhong-peng
authors.initials: ZP
authors.lastname: Guo
authors.forename: Zhong-yang
authors.initials: ZY
authors.lastname: Ding
authors.forename: Gui-yang
authors.initials: GY
authors.lastname: Shi
mesh_terms: D000693:Anaerobiosis; D001409:Bacillus cereus / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D008954:Models, Biological; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D009243:NAD; C036909:lignocellulose; D000431:Ethanol; D009249:NADP; D008031:Lignin; D005990:Glycerol