Cellulosic alcoholic fermentation using recombinant Saccharomyces cerevisiae engineered for the production of Clostridium cellulovorans endoglucanase and Saccharomycopsis fibuligera β-glucosidase

In this study, Saccharomyces cerevisiae was engineered for simultaneous saccharification and fermentation of cellulose by the overexpression of the endoglucanase D (EngD) from Clostridium cellulovorans and the β-glucosidase (Bgl1) from Saccharomycopsis fibuligera. To promote secretion of the two enzymes, the genes were fused to the secretion signal of the S. cerevisiae α mating factor gene. The recombinant developed yeast could produce ethanol through simultaneous production of sufficient extracellular endoglucanase and β-glucosidase. When direct ethanol fermentation from 20 g L^-1 β-glucan as a substrate was performed with our recombinant strains, the ethanol concentration reached 9.15 g L^-1 after 50 h of fermentation. The conversion ratio of ethanol from β-glucan was 80.3% of the theoretical ethanol concentration produced from 20 g L^-1 β-glucan. In conclusion, we have demonstrated the construction of a yeast strain capable of conversion of a cellulosic substrate to ethanol, representing significant progress towards the realization of processing of cellulosic biomass in a consolidated bioprocessing configuration.