Improving isobutanol tolerance and titers through EMS mutagenesis in Saccharomyces cerevisiae.

Abstract

Improving yeast tolerance toward isobutanol is a critical issue enabling high-titer industrial production. Here, we used EMS mutagenesis to screen Saccharomyces cerevisiae with greater tolerance toward isobutanol. By this method, we obtained EMS39 with high-viability in medium containing 16g/L isobutanol. Then, we metabolically engineered isobutanol synthesis in EMS39. About 2μ plasmids carrying PGK1p-ILV2, PGK1p-ILV3 and TDH3p-cox4-ARO10 were used to over-express ILV2, ILV3 and ARO10 genes, respectively, in EMS39 and wild type W303-1A. And the resulting strains were designated as EMS39-20 and W303-1A-20. Our results showed that EMS39-20 increased isobutanol titers by 49.9% compared to W303-1A-20. Whole genome resequencing analysis of EMS39 showed that more than 59 genes had mutations in their open reading frames or regulatory regions. These 59 genes are enriched mainly into cell growth, basal transcription factors, cell integrity signaling, translation initiation and elongation, ribosome assembly and function, oxidative stress response, etc. Additionally, transcriptomic analysis of EMS39-20 was carried out. Finally, reverse engineering tests showed that overexpression of CWP2 and SRP4039 could improve tolerance of S.cerevisiae toward isobutanol. In conclusion, EMS mutagenesis could be used to increase yeast tolerance toward isobutanol. Our study supplied new insights into mechanisms of tolerance toward isobutanol and enhancing isobutanol production in S. cerevisiae.