1-32: Effect of the exogenous gene xylA on the ability of S. cerevisiae to grow on xylose

The production of fuel ethanol has increased many fold over the last decade due in part to increasing fossil fuel prices and environmental concerns. After the six carbon sugar, glucose, the next most abundant component of cellulases is the five carbon sugar xylose. However, the utilization of xylose is slow compared to that of glucose. The fermentation of xylose to ethanol is achieved in S. cerevisiae by genetic engineering. In this work presented herein, we have constructed a yeast strain expressing the xylose isomerase gene xylA from the anaerobic fungus Piromyces Sp. strain E2. To investigate the cellular processes impacted by the introduction of an exogenous gene, we utilized a genome wide synthetic lethal screen. We identified 59 deletion mutants that were sensitive to the XylA gene in the presence of xylose and 2 deletion mutants that preformed better upon transformation with the xylA gene in the presence of xylose. We also examined the changes in the transcriptome in the presence or absence of xylose and observed 113 up regulated and 92 down regulated genes, most notably genes involved in the pentose phosphate pathway.