Engineering of a Novel Cellulose-Adherent Cellulolytic Saccharomyces Cerevisiae for Cellulosic Biofuel Production

Cellulosic biofuels are still impeded by the recalcitrance of lignocellulose that requires high dosages of cellulase to hydrolyze. Several cellulolytic yeast strains have been developed to reduce the need for enzyme addition, but exhibiting limited effect. This is because of the insufficient cellulolytic activity provided by yeast, and lacks of a novel strategy to achieve efficient cellulose degradation using cellulolytic strains. Here, we report the successful engineering of a high-efficiency cellulolytic Saccharomyces cerevisiae by displaying four different synergistic cellulases (β-glucosidase, endoglucanase, cellobiohydrolase I, and cellobiohydrolase II) on the cell surface. The cellulase-displaying yeast strain exhibited clear cell-to-cellulose adhesion and a “tearing” cellulose degradation pattern; its adhesion ability is correlated with enhanced surface area and roughness of the target cellulose fibers, resulting in higher hydrolysis efficiency. The engineered yeast could directly produce ethanol from rice straw, as well as cutting down more than 40% of the required enzyme dosage under high-dense fermentation process. We provided a novel strategy that increases cellulose hydrolysis via enhancing cell-to-cellulose interactions, and demonstrate a breakthrough in making the feasibility of cellulosic biofuel production.

Keyword: cell-surface display; cellulase; cellulose-adherent; cellulosic ethanol; Saccharomyces cerevisiae