Breeding of Industrial Diploid Yeast Strain with Chromosomal Integration of Multiple β-Glucosidase Genes

We constructed a double auxotrophic OC-2 industrial diploid strain of Saccharomyces cerevisiae and introduced 4 copies of cell surface displaying β-glucosidase (BGL) genes into the chromosome. The engineered OC-2 strain showed 5-fold higher BGL activity compared with the yeast carrying 2 copies of BGL gene and directly produced ethanol from cellobiose.