Continuous co-fermentation of cellobiose and xylose by engineered Saccharomyces cerevisiae

Simultaneous fermentation of cellobiose and xylose by an engineered Saccharomyces cerevisiae has been demonstrated in batch fermentation, suggesting the feasibility of continuous co-fermentation of cellulosic sugars. As industrial S. cerevisiae strains have known to possess higher ethanol productivity and robustness compared to laboratory S. cerevisiae strains, xylose and cellobiose metabolic pathways were introduced into a haploid strain derived from an industrial S. cerevisiae. The resulting strain (JX123-BTT) was able to ferment a mixture of cellobiose and xylose simultaneously in batch fermentation with a high ethanol yield (0.38g/g) and productivity (2.00g/L·h). Additionally, the JX123-BTT strain co-consumed glucose, cellobiose, and xylose under continuous culture conditions at a dilution rate of 0.05h^-1 and produced ethanol resulting in 0.38g/g of ethanol yield and 0.96g/L·h of productivity. This is the first demonstration of co-fermentation of cellobiose and xylose by an engineered S. cerevisiae under continuous culture conditions.