Globally Overexpressed Xylose Metabolic Pathway in Saccharomyces Cerevisiae Produces Highly Efficient Ethanol Production from Lignocellulose Hydrolysates

Abstract

The biggest challenge of using 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 eight xylose metabolic genes (named 8G) and a transcription factor SPT2 (named SPT2^OE), and their efficacy in fermentation was evaluated in a simulated corn hydrolysate, resulting in two favored strains 8G-3 and SPT2^OE. SPT2^OE exhibited high ethanol production of 70.7 g/L in ball milling-based hydrolysate and conversion rates close to peak value in corn hydrolysates as early as within 24 h. Moreover, SPT2^OE 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 unprecedented results of ethanol yield and titer in different hydrolysates.

Keywords: Saccharomyces cerevisiae, xylose, transcriptome analysis, ethanol, lignocellulosic hydrolysate