Abstract: Recombinant genetic constructs and strains of H. polymorpha having significantly increased ethanol productivity with a simultaneous decreased production of xylitol during high-temperature xylose fermentation are disclosed. The constructs include a H. polymorpha XYL1 gene encoding xylose reductase mutated to decrease affinity of the enzyme toward NADPH. The modified version of XYL1 gene under control of a strong constitutive HpGAP promoter was overexpressed in a ?xyl1 background. A recombinant H. polymorpha strain overexpressing the mutated enzyme together with native xylitol dehydrogenase and xylulokinase in the ?xyl1 background was also constructed. Xylose consumption, ethanol and xylitol production by the constructed strain were evaluated during high-temperature xylose fermentation (48° C.). A significant increase in ethanol productivity (up to 7.4 times) was shown in the recombinant strain as compared with the wild type strain.

Abstract: Recombinant genetic constructs and strains of H. polymorpha having significantly increased ethanol productivity with a simultaneous decreased production of xylitol during high-temperature xylose fermentation are disclosed. The constructs include a H. polymorpha XYL1 gene encoding xylose reductase mutated to decrease affinity of the enzyme toward NADPH. The modified version of XYL1 gene under control of a strong constitutive HpGAP promoter was overexpressed in a ?xyll background. A recombinant H. polymorpha strain overexpressing the mutated enzyme together with native xylitol dehydrogenase and xylulokinase in the ?xyll background was also constructed. Xylose consumption, ethanol and xylitol production by the constructed strain were evaluated during high-temperature xylose fermentation (48° C.). A significant increase in ethanol productivity (up to 7.4 times) was shown in the recombinant strain as compared with the wild type strain.