Monday, May 5, 2008
7-52

Ethanol Impact on Xylose Metabolism in S. cerevisiae 424A(LNH-ST)

Arun Athmanathan1, Miroslav Sedlak2, Nancy W. Y. Ho3, and Nathan S. Mosier1. (1) LORRE/Ag. and Bio. Engineering, Purdue University, 500 Central Drive, West Lafayette, IN 47907, (2) Lorre/abe, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907, (3) LORRE/Chemical Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907

Ethanol toxicity could be a significant bottleneck in industrial ethanol
fermentation of sugars from lignocellulose. To understand ethanol impact
on xylose fermentation, batch fermentations were carried out using S.
cerevisiae
424A (LNH-ST), an engineered strain capable of co-fermenting
glucose and xylose. The fermentation of xylose was carried out in YEP
growth media, using largely non-growing cells in the presence of initial
ethanol concentrations between 4 - 8% (w/v). The effects of extraneously
added ethanol (pure xylose fermentation) and ethanol generated from
glucose equivalent (co-fermentation) are compared. This yeast strain was
found to cease fermentation of xylose at an extraneously added ethanol
concentration of 9% (w/v).  However, co-fermentation of glucose and
xylose was capable of achieving a final ethanol titer over 11% (w/v). A
preliminary unstructured, Monod-type model of these batch fermentations
that include ethanol inhibition is presented.