Sunday, April 29, 2007
1B-68

Combined effect of acetic acid and pH on the cofermentation of glucose and xylose by recombinant yeast

Miroslav Sedlak, Lorre/abe, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907, Haroon Mohammad, LORRE/Agricultural and Biological Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907, Nancy W. Y. Ho, LORRE/Chemical Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907, and Nathan S. Mosier, LORRE/Ag. and Bio. Engineering, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907.

Cellulosic biomass is known to be an ideal raw material for the production of chemicals by microbial processes, particularly those produced in large volumes such as ethanol. However, conversion of lignocellulose into fermentable sugars (hydrolysates) also produces a wide range of compound that are inhibitory to microbial fermentation. The inhibitory compound in hydrolysates can derivate from sugar degradation (furfural, HMF), pretreatment release (acetic acid) and lignin degradation. In this report we have investigated the effect of acetic acid on the co-fermentation of glucose and xylose by our genetically modified S. cerevisiae 424A(LNH-ST). The co-fermentation of glucose/xylose was performed in presence of 5, 10, 15g/L of acetic acid over a pH range 4.5 - 6.5. The fermentation of both sugars was influenced by acetic acid and pH. Generally, lowering the pH increases the inhibitory effect of acetic acid. Our results also show that utilization of xylose is more affected by acetic acid concentration and lower pH than glucose.

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