(409g) High-Efficient Biobutanol Production from Lignocellulosic Feedstocks By Developing Metabolic and Bioprocessing Engineering Approaches of Clostridium Acetobutylicum

Corn stover is evaluated as the most favorable candidate feedstock for lignocellulosic butanol production via microbial acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum. In the presence of pretreatment-derived inhibitors, however, intracellular ATP and NADH involved in cell growth, butanol biosynthesis and stress response, are exceedingly challenged owing to its disrupted sugar transport system. Therefore, there is a necessity to develop effective engineering approach to overcome these limitations for high-efficient lignocellulosic butanol production. C. acetobutylicum as a hyper butanol producer could not simultaneously utilize glucose and xylose due to glucose-mediated carbon catabolite repression on xylose metabolism. In this project, metabolic engineering of C. acetobutylicum was first performed by heterologous expressions of xylonate biosynthetic enzymes (XylB and XylC) from Caulobacter crescentus, which resulted in efficient glucose/xylose co-utilization and cofactor NADH compensation. Efficient strategy for lignocellulosic butanol production was then established integrated with extracellular pH regulation. During batch glucose/xylose culture by the engineered strain, improvements on butanol production and productivity were obtained within 24 h with ~20% and ~200% increases compared to those of the wildtype strain. When using non-detoxified corn stover hydrolysate as substrate, butanol production and productivity were dramatically increased by 3- and 6-fold times, respectively. Pleiotropic roles at global levels were also elaborated to elucidating regulatory mechanisms associated with stress tolerance, biological detoxification as well as central carbon metabolism. Based on these above, the combined metabolic and bioprocess engineering approaches developed in this project not only provide new cues for engineering C. acetobutylicum, but contribute to lignocellulose-derived biorefinery and make lignocellulosic butanol production more economically viable and competitive.