Sunday, May 3, 2009
2-23
Identification of Saccharomyces cerevisiae genes involved in the resistance to phenolic fermentation inhibitors
Linda Björklund, AstraZeneca R&D Lund, SE-221 87 Lund, Sweden, Simona Larsson, Riga Technical University, Faculty of Civil Engineering, Riga LV 10483, Latvia, and Leif J. Jönsson, Department of Chemistry, Umeå University, SE-901 87, Umeå, Sweden.
Saccharomyces cerevisiae was exposed to toxic concentrations of three phenolic phenylpropane derivatives: coniferyl aldehyde, ferulic acid and isoeugenol. DNA microarray analysis was employed as one of the tools 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: yap1D, atr1D, and flr1D. The rate of reduction of coniferyl aldehyde to coniferyl alcohol decreased six-fold when the gene coding for the transcriptional activator Yap1p was deleted and to a lesser extent (three-fold) 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 the same compound 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.