Identification of Saccharomyces cerevisiae Genes Involved in the Resistance to Phenolic Fermentation Inhibitors

Saccharomyces cerevisiae was exposed to inhibitory concentrations of the three phenolic phenylpropanoids: coniferyl aldehyde, ferulic acid, and isoeugenol. Deoxyribonucleic acid microarray analysis was employed as one approach to generate a set of candidate genes for deletion mutant analysis to determine the potential contribution of the corresponding gene products to the resistance against toxic concentrations of phenolic fermentation inhibitors. Three S. cerevisiae deletion mutants with increased sensitivity to coniferyl aldehyde were identified: yap1Δ, atr1Δ, and flr1Δ. The rate of reduction of coniferyl aldehyde to coniferyl alcohol decreased sixfold when the gene encoding the transcriptional activator Yap1p was deleted, and threefold when the Yap1p-controlled genes encoding Atr1p and Flr1p were deleted. Growth, glucose consumption, and ethanol formation progressed after a lag phase during which coniferyl aldehyde reduction and coniferyl alcohol formation occurred. The results link ATR1, FLR1, and YAP1 by their ability to confer resistance to coniferyl aldehyde and show that deletion of any of these three genes impairs the ability of S. cerevisiae to withstand coniferyl aldehyde and detoxify it by reduction. Furthermore, the results suggest that overexpression of ATR1, FLR1, and YAP1 is of interest for the construction of novel yeast strains with improved resistance against inhibitors in lignocellulose hydrolysates.