Tuesday, April 30, 2013
Exhibit Hall
The economically sustainable use of cellulosic feedstocks as substrates for microbial bioconversion to biofuels presents numerous challenges, including the presence of inhibitory compounds, and carbon sources that are difficult to ferment. Scheffersomyces stipitis is a yeast with the native capacity to ferment xylose to ethanol. We have developed genetic tools for S. stipitis to integrate additional copies of sugar transporters and overexpression cassettes for key xylose assimilation genes. By employing rational metabolic engineering in combination with mating and adaptation we have developed strains of S. stipitis that exhibit improved growth and fermentative performance in industrial cellulosic hydrolysates. In conjunction with strain development efforts, we implemented process improvements that led to a significant reduction in time required to achieve peak ethanol in batch bioreactor culture of cellulosic sugar solutions.