Genetic engineering of yeasts to improve ethanol production from xylose

Saccharomyces cerevisiae, expressing xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) genes from Pichia stipitis, has the ability to produce ethanol from xylose. To improve ethanol production, three recombinant strains of F102X (fps1Δ), F104X (fps1Δ gpd2Δ) and F106X (fps1Δ gpd2Δ GLN1) with TKL1, TAL1, RKI1, RPE1, XYL1, XYL2 and XKS1 overexpression were constructed in this study. Compared to the control strain FB3X, ethanol production from xylose in strains F102X, F104X and F106X was increased by 4.3, 9.5 and 17.2%, respectively. F106X produced 18.2% less glycerol from a glucose-xylose mixture medium than FB3X, whereas no glycerol production was detected in these four strains when grown on a xylose medium. In addition, the xylitol production and ethanol yield in strain F106X did not differ significantly. These results suggested that the improvement in ethanol production in strain F106X was mainly due to increased xylose consumption.