Here, we propose to engineer S. cerevisiae to efficiently utilize xylose as a carbon source and produce the ideal biofuel isobutanol. While our previous efforts to engineer high-level production of isobutanol in S. cerevisiae suffered from the yeasts innate preference for ethanol production under high glucose concentration (the Crabtree effects), we believe that we can overcome this metabolic barrier by switching the carbon source to xylose and introduce the appropriate xylose utilization pathway into S. cerevisiae. Specifically, we plan to exploit the lower glycolytic pathway that is caused by xylose utilization and redirect the carbon away from ethanol production and towards isobutanol production. In short, the proposed research will yield an engineered S. cerevisiae strain that can efficiently convert xylose as well as lignocellulose hydrolysates from agricultural wastes into isobutanol. We envision that our work will provide a versatile and commercially feasible production platform for fuels and chemicals.
Within the next 2 years, the following Specific Aims will be pursued:
Aim 1. Overexpression of the optimized xylose assimilation pathway in the yeast Saccharomyces cerevisiae;
Aim 2. Lab evolution engineering of the strain described in Aim 1 to further enhance xylose utilization and cell growth;
Aim 3: Overexpression of the isobutanol pathway into the engineered xylose-fermenting S. cerevisiae and test the strain performance on xylose and lignocellulose hydrolysates.
