The four-carbon branched-chain higher alcohol, isobutanol, is an attractive advanced biofuel with fuel properties superior to ethanol. However, its toxicity to cells presents a major challenge when engineering microbes to produce it at economically competitive titers. In this work, we screened the Saccharomyces cerevisiae gene-deletion library to identify genes involved in isobutanol tolerance. We found that strains lacking genes encoding NADPH-generating enzymes in the pentose phosphate pathway are hypersensitive to isobutanol and other higher alcohols, but not to ethanol. In contrast, deletion of a transcriptional activator involved in nitrogen catabolite repression significantly increases yeast tolerance specifically to branched-chain higher alcohols. Transcriptomic data revealed that isobutanol prompts a nitrogen starvation response, which upregulates amino acid biosynthesis and nitrogen import while downregulating glycolysis, cell wall biogenesis, and membrane lipid biosynthesis, processes important for cell growth. Furthermore, we found that deletion of a single gene can disrupt this response, enhancing tolerance and boosting isobutanol production as much as 4.9-fold in engineered strains. This study illustrates how gene deletions can boost production by evading adaptive mechanisms to tolerate stress.

Genomics and transcriptomics reveal genes involved in isobutanol tolerance and production in Saccharomyces cerevisiae

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.