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.
Cofactor-regulation Ethanol yields Glycerol production Saccharomyces cerevisiae
The authors gratefully acknowledge Prof. Suren Singh (Department of Biotechnology and Food Technology, Durban University of Technology, South Africa) for critically reading the manuscript. This work was financially supported by the Fundamental Research Funds for the Central Universities (JUSRP21122), Innovative Research Team of Jiangsu Province in Universities, and the Program of Introducing Talents of Discipline to Universities (No. 111-2-06).
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