Tolerance to isobutanol toxicity is mediated by a transcriptional factor Znf1 of pentose phosphate pathway

The production of biofuels from renewable biomass such as grain and wood are facilitated by microbes including bacteria or yeast. Bioethanol is regarded as one of the carbon-neutral products of useful biofuel; however, its low energy content and high hygroscopicity are viewed as disadvantages. In terms of fuel quality, biobutanol is more preferable to ethanol because of various significant advantages associated such as its higher energy density and lower hygroscopicity. Moreover, the branched-chain structure of isobutanol provides a higher octane number than the isomeric n-butanol. It is naturally produced in the low amount in the cytosol by the Ehrlich pathway by the yeast S. cerevisiae. Isobutanol toxicity to host has still limited the yield of product. In this study, we aimed to address the role of transcriptional regulators of stress response in mediating expression of genes in the pentose phosphate pathway to enhance yeast tolerance to isobutanol. We also attempted to identify key factors involved in reduction of isobutanol toxicity using several deletion mutants of S. cerevisiae including Δtal1, Δtkl1, Δrpe1, Δzwf1, Δgnd1 strains. Deletion of Znf1 significantly deceased cell dry weight under high concentrations of isobutanol. Our results implicated the zinc cluster Znf1 as a key transcription factors of these genes. Thus, the engineered strain with overexpression of ZNF1 gene could potentially improve production of isobutanol as well as enhance isobutanol tolerance what is possible for bio-based isobutanol production