Jin-Hee Kim1, Jiri Adamec1, Nathan S. Mosier2, Nancy W. Y. Ho3, and Miroslav Sedlak2. (1) Bindley Bioscience Center/LORRE, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (2) LORRE/Ag. and Bio. Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (3) LORRE/Chemical Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907
Efficient conversion of hemicellulose-derived sugars to ethanol at high yields and titers are goals toward commercializing cellulosic ethanol production. S. cerevisiae 424A (LNH-ST) developed at Purdue University can efficiently ferment glucose and xylose. However, increasing ethanol titers reduces yeast growth rate and fermentation rates, especially xylose fermentation.Ethanol concentrations over 60g/L start to have deteriorating effects on xylose fermentation by our S. cerevisiae 424A (LNH-ST) strain, while concentrations >90g/L are required to have similar effects on glucose fermentation in this strain. For this reason, it is critical to understand the ethanol stress response, especially when a different carbon source is fermented. Through adaptation we have developed a new strain with improved xylose fermentation compared to the original strain. The new strain has 500% higher ethanol volumetric productivity on xylose in the presence of higher ethanol concentrations (above 6%) than the original strain. In this paper, we use a system biology approach to analyze differences between our original strain and newly developed strain. We focus not only on expression profiling (transcriptomics), since many genes and gene regulations are involved in ethanol tolerance but also on lipidomics because membrane lipids composition is closely related to membrane fluidity which could be one of the key to increase ethanol tolerance.
