Chia-Ling Wu1, Nathan S. Mosier1, Jiri Adamec2, Nancy W. Y. Ho3, and Miroslav Sedlak1. (1) LORRE/Ag. and Bio. Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (2) Bindley Bioscience Center, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (3) LORRE/Chemical Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907
Bio-ethanol has gained much attention due to its economical and environmental benefits as a renewable fuel. Our lab has genetically engineered a yeast strain 424A (LNH-ST) that can co-ferment glucose and xylose, the two most abundant sugars in cellulosic biomass. However, several inhibitors such as acetic acid, furfural, and ethanol are created and accumulated during the process of cellulosic biomass pretreatment, hydrolysis, and/or during fermentation. Our previous work has shown that acetic acid under process relevant conditions do not significantly affect glucose fermentation. However xylose utilization is significantly affected, especially at low pH environment (pH < 5.5) and high acetic acid concentration (> 10 g/L).An acetic acid-resistant yeast strain alternated from original 424A (LNH-ST) strain was developed by adaptation to acetic acid. Small-scale fermentation (100 ml YEP) containing 120 g glucose and 80 g xylose per L with 10 g acetic acid per L has shown more than triple the rate of xylose utilization (1.05 g/L/h from 0.32 g/L/h) and higher final ethanol titer (76.3 g/L from 61.2 g/L) by the new strain compared to the original strain. In this study, a system biology analysis including transcriptomic and metabolomic measurements were completed to understand gene expression and metabolic fluxes in this improved strain as compared to the original strain.
