Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Acetate is an unavoidable by-product generated from acetylated hemicellulose and lignin in the process of biomass hydrolysis. The removal of acetate from hydrolysate is necessary since acetate inhibits microbial production of biofuel. This study focuses on selective consumption of acetate without sugar degradation from a mixture of sugars and acetate. As a first step, fifteen Escherichia coli strains were compared for maximum specific growth rate (µMAX) using 5 g/L acetate as the sole carbon source. From the results of the experiments, we observed that E. coli C (ATCC8739) had the greatest growth rate (0.405 h-1) on acetate while SCS-1 strain had the slowest growth rate (0.153 h-1). The triple-knockout strain C ptsG glk manZ (ALS1363) consumed 10 g/L acetate within 14.0 h and subsequently consumed glucose after the complete consumption of acetate. Similar results were obtained with the C ptsG glk manZ crr (ALS1364) strain except that acetate was consumed in 23.0 h. The crr knockout did not prevent subsequent glucose consumption. We also present results on the enzymatic and genetic differences between these E. coli strains and their correlation with acetate consumption.