Improvement of ethanol production in Saccharomyces cerevisiae by hetero-expression of GAPN and FPS1 deletion.

BACKGROUND: During anaerobic bioethanol fermentation of Saccharomyces cerevisiae, the main byproduct glycerol is essential to regulate redox balance (reoxidize NADH to NAD+), which is necessary to maintain cell growth and fermentation. Hetero-expression of a NADP+-dependent glyceraldehydes-3-phosphate dehydrogenase (GAPN) [EC.1.2.1.9] in S. cerevisiae could redirect the carbon flux from glycerol to ethanol involving a net oxidation of NADH. The present study investigates whether combination of GAPN hetero-expression and glycerol exporter Fps1p disruption would result in less glycerol and more ethanol production without affecting growth rate during anaerobic fermentations. RESULTS: The results of anaerobic fermentations showed that the fps1Δ mutant with GAPN (named 4FG) produced 21.47% less glycerol and 9.18% more ethanol compared with a parental strain with a control plasmid, while the rates of growth and fermentation were not changed. Moreover, the engineered strain 4FG yielded less glycerol and acetic acid, and more ethanol than the control, fps1Δ mutant or with GAPN only. CONCLUSIONS: During anaerobic fermentations, hetero-expression of GAPN restored the reduced grow rate of the fps1Δ mutant, and led to less byproducts and more ethanol production. This combination strategy could be used to modulate glycerol metabolism and optimize the anaerobic fermentation of S. cerevisiae. Copyright © 2011 Society of Chemical Industry