Metabolic Engineering of Saccharomyces cerevisiae to Improve Glucan Biosynthesis

β-Glucan is a chief structural polymer in the cell wall of yeast. β-Glucan has attracted intensive attention because of its wide applications in health protection and cosmetic areas. In the present study, the β-glucan biosynthesis pathway in S. Cerevisiae was engineered to enhance β-glucan accumulation. A newly identified bacterial β-1, 6-glucan synthase GsmA from Mycoplasma agalactiae was expressed, and increased β-glucan content by 43%. In addition, other pathway enzymes were investigated to direct more metabolic flux towards the building of β-glucan chains. We found that overexpression of Pgm2 (phosphoglucomutase) and Rho1 (a GTPase for activating glucan synthesis) significantly increased β-glucan accumulation. After further optimization of culture conditions, the β-glucan content was increased by 53.1%. This study provides a new approach to enhance β-glucan biosynthesis in Saccharomyces cerevisiae.