Xylose fermentation by Saccharomyces cerevisiae using endogenous xylose-assimilating genes

OBJECTIVES: To genetically engineer Saccharomyces cerevisiae for improved ethanol productivity from glucose/xylose mixtures. RESULTS: An endogenous gene cassette composed of aldose reductase (GRE3), sorbitol dehydrogenase (SOR1) and xylulose kinase (XKS1) with a PGK1 promoter and a terminator was introduced into two S. cerevisiae strains, a laboratory strain (CEN.PK2-1C) and an industrial strain (Kyokai No. 7). The engineered Kyokai No. 7 strain (K7-XYL) exhibited a higher sugar consumption rate (1.03 g l⁻¹ h⁻¹) and ethanol yield (63.8 %) from a glucose and xylose mixture compared to the engineered CEN.PK2-1C strain. Furthermore, K7-XYL produced a larger amount of ethanol (39.6 g l⁻¹) compared to K7-SsXYL (32 g l⁻¹) with integrated xylose reductase and xylitol dehydrogenase from a xylose-assimilating yeast Scheffersomyces stipitis instead of GRE3 and SOR1. CONCLUSION: The created S. cerevisiae strain showed sufficient xylose-fermenting ability to be used for efficient ethanol production from glucose/xylose.