(687b) High-Efficient Butanol Production from Lignocellulosic Biomass By Developing Metabolic Engineering and Process Intensification Approaches

Corn stover is evaluated as the most favorable candidate feedstock for lignocellulosic butanol production via microbial acetone-butanol-ethanol (ABE) fermentation by Clostridium spp. 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, C. acetobutylicum was metabolically engineered by introducing xylonate-producing pathway from Caulobacter crescentus, which contributed to both glucose/xylose co-utilization and NADH compensation. Efficient strategy for lignocellulosic butanol production was then established via extracellular pH and electron carrier regulation. During batch glucose/xylose culture by engineered strain, improvements on butanol production and productivity were achieved with 20% and 200% increases compared to those of the wildtype strain. When using non-detoxified lignocellulosic hydrolysate, butanol production and productivity were also 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 also make lignocellulosic butanol production more economically viable and competitive.