Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
The importance of biofuel ethanol is growing as the demand for clean, renewable fuels produced from non-food sources increases. As an alternative to corn-based ethanol, this study explores a method to create ethanol from sugar mixtures representative of switchgrass, a cellulosic biomass, using the native yeast Saccharomyces pastorianus. This method utilizes the simultaneous isomerization and fermentation of xylose, a sugar that makes up 40% of hydrolyzed switchgrass, to xylulose via the enzyme xylose isomerase. The use of xylose isomerase, under conditions suitable for yeast growth, enhances ethanol production by up to 12%, resulting in the conversion of 45% of sugars to ethanol (89% theoretical yield), in addition to cell mass production. The long term goal of this research is to produce ethanol cost effectively from hydrolyzed switchgrass using S. pastorianus and the enzyme xylose isomerase.
S. pastorianus is commonly used by the brewing industry for the production of lager beer. It is a hybrid of S. bayanus and S. cerevisiae, and has retained characteristics of both species. Notably, S. pastorianus is able to grow and ferment sugar at low temperatures while maintaining a high tolerance to ethanol. A portion of the S. pastorianus genome was sequenced during this study and showed the highest identity (1251/1257 nucleotide matches) to S. pastorianus.