(191a) Systems Biology Analysis of the Effect of Acetic Acid On S. Cerevisiae 424A(LNH-ST) and Resistant Strains During the Co-Fermentation of Glucose and Xylose

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, inhibitors present in cellulosic feedstocks (acetic acid) and the desired fermentation product (ethanol) reduce yeast growth rate and fermentation rates, especially during xylose fermentation.

Through selective culturing, we have developed new, evolved strains with improved xylose fermentation compared to the original strain.  Under control fermentations (no acetic acid), the new strain consumes xylose (g/g cells/hr) 2.2 times faster than the original strain.  When challenged with acetic acid (10 g/L), the rate of xylose consumption drops almost 90% in the control strain compared to a drop of only 47% in the evolved strain. We present the results from a system biology approach to analyzing differences between our original strain and newly developed strains.   We report differences between the strains and the effect of acetic acid on both.  Data from the concentrations of intracellular metabolites as well as gene expression for multiple points during batch fermentations are analyzed to give insights into changes in the evolved strain.