No abstract

No abstract

In order to achieve rapid xylose utilization in the presence of acetate, improved yeast strains were engineered for higher bioethanol production. First, a six-gene cluster, including XYL1/XYL2/XKS1/TAL1/PYK1/MGT05196, was generated by using an in-depth two-stage (glucose and xylose) transcription reprogramming strategy in an evolutionary adapted strain of CE7, resulting in two improved engineered strains WXY46 and WXY53. Through a combined screening of xylose and glucose stage-specific promoters between tricarboxylic acid (TCA)/HSP and constitutive types, respectively, WXY46 with the constitutive promoters showed a much higher ethanol yield than that of WXY53 with the TCA/HSP promoters. Second, an optimized strain WXY74 was obtained by using more copies of a six-gene cluster, which resulted in a higher ethanol yield of 0.500 g/g total sugars with acetate conditions. At last, simultaneous saccharification and co-fermentation were performed by using the evolved WXY74 strain, which produced 58.4 g/L of ethanol from wheat straw waste and outperformed previous haploid XR-XDH strains.

Aims:  To investigate the effect of FPS1 deletion on the fermentation properties of Saccharomyces cerevisiae and to evaluate whether FPS1 deletion would result in higher ethanol yield. Methods and Results:  FPS1 of S. cerevisiae was knocked out using the one‐step gene replacement method. The fermentation properties of the fps1Δ mutant under microaerobic conditions were investigated and compared with that of the wild type. Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid and pyruvic acid were monitored. Compared with the wild type, the ethanol yield of the fps1Δ mutant was improved by 10 ± 2% and glycerol yield decreased by 18·8 ± 2%. Meanwhile, acetic acid yield decreased by 5·4 ± 1%, and pyruvic acid yield decreased by 58·6 ± 1%. Conclusions:  FPS1 deletion of S. cerevisiae resulted in reduced glycerol yield and higher ethanol yield. Significance and Impact of the Study:  The cost of carbon source in ethanol fermentation is an important factor in determining ethanol production. Approximately 5% carbon source is converted into glycerol in ethanol fermentation. Eliminating formation of glycerol through FPS1 deletion can be used to increase ethanol yield of S. cerevisiae without increasing the overall cost of carbon source.