Global reprogramming of xylose metabolism in Saccharomyces cerevisiae efficiently produces ethanol from lignocellulose hydrolysates

The biggest challenge of utilizing lignocellulosic feedstocks for efficient ethanol fermentation is to improve strains and processes capable of mixed sugar fermentation in the presence of released inhibitors. A previously reported Saccharomyces cerevisiae strain WXY70 was further engineered to overexpress up to eight xylose metabolic genes or a transcription factor SPT2, and their efficacy in fermentation was evaluated in a simulated corn hydrolysate, resulting in two favored strains 8G-3 and SPT2OE. SPT2OE produced 0.503 and 0.508 g ethanol/g total sugars in ball milling-based and corn hydrolysates, respectively, within 24 h. Moreover, SPT2OE produced about 40 g/L ethanol from 120 g/L xylose mother liquid solution. Overall, the fermentation performance of SPT2 overexpression was superior to recently reported SFA1 overexpression and achieved promising results of ethanol yield and titer in different hydrolysates.