Adaptive Evolution of Saccharomyces Cerevisiae to Improve Ethanol Production From Corn Cob Hydrolyzate Under High Temperature

To improve cellulosic ethanol yield and develop the cost-effective simultaneous saccharification fermentation for ethanol production, the strain should be developed with improved tolerance to high temperature and inhibitory compounds from lignocellusic biomass. Here, an industrial strain of S. cerevisiae Ethanol Red E491 (Ethanol Performance Group, NJ, USA) was evolved using corn cob hydrolyzate at step-increased temperature (from 37-42°C) and the resulting daughter strain, TIB-S.C Y01, produced ethanol much more rapidly than its parent in fermentations of corn cob hydrolyzate at 42°C. Adaptation improved fermentation performance of the evolved strain. Based on transcriptome analysis of parent and evolved strains via RNA sequencing, we find evidence of dramatic up/down-regulation in Bsc1p, Hxk2p, Pfk27p, Mer1p, Gnd1p, and Tkl1p genes. Consistent with the complex, multigenic nature of multiple stresses, we observe adaptations in a diversity of cellular processes, implying a rugged fitness landscape for the tolerance of high temperature and inhibitory compounds in yeast.