Development of Cellobiose-utilizing Recombinant Yeast for Ethanol Production from Cellulose Hydrolyzate

A cellobiose-utilizing recombinant yeast having β-glucosidase activity was developed for ethanol production from a mixture of glucose and cellobiose. Using δ-sequences of Ty1 transposon of yeast as target sites for homologous recombination, a heterologous gene of β-glucosidase was integrated into the chromosome of Saccharomyces cerevisiae. The δ-integrated recombinant yeast, Saccharomyces cerevisiae L2612 (pδ-BGL), showed perfect mitotic stability even in nonselective media and showed ca. 1.5 fold higher β-glucosidase activity than the recombinant yeast harboring the 2μ-based plasmid vector system. A mathematical model was developed to describe the β-glucosidase formation and ethanol production from the Saccharomyces cerevisiae L2612 (pδ-BGL). The model newly described that the heterologous β-glucosidase production mediated by ADH1 promoter is regulated by glucose and repressed by ethanol.