18566: Overexpression of YDR049W and HMG1 in Saccharomyces cerevisiae to improve furfural tolerance

Bioethanol is an alternative fuel that will lessen our need for fossil fuels.  The current method of fermenting ethanol with Saccharomyces cerevisiae uses agricultural products such as cornstarch. However, these substrates will not be sufficient to keep up with our fuel demands since there is a finite supply of these substrates and they compete with human and livestock consumption.  Fortunately, alternative substrates, such as lignocellulosic biomass, are abundant, yet are not effectively used.  An obstacle to using lignocellulosic biomass is that the process used to release useable sugars, also generates fermentation inhibitors (i.e. furfural, hydroxymethylfurfural, and vanillin).  Our objective is to genetically engineer robust yeast that can survive in the presence of these inhibitors.  Our strategy uses genes previously linked to inhibitor tolerance.  The gene ZWF1, which produces NADPH, when overexpressed was shown previously to provide increased inhibitor tolerance and decreased cellular damage.  To build upon these observations two other genes, YDR049W and HMG1, were overexpressed by themselves and in combination with ZWF1.   YDR049W encodes a transcription factor linked to vanillin, HMF, and furfural tolerance.  HMG1 is a NADPH dependent reductase that functions in ergosterol biosynthesis, which has previously been linked to inhibitor tolerance. Overexpressing YDR049W resulted in improved growth in the presence of furfural with less internal cellular damage.  Co-overexpression of YDR049W with ZWF1 had slightly improved growth.  HMG1 did not display the same improved furfural tolerance.  Additional genetic strategies are being pursued with these yeast to obtain robust yeast capable of tolerating multiple inhibitors during lignocellulosic fermentation.