3 years ago

Improving Fructose Utilization and Butanol Production by Clostridium acetobutylicum via Extracellular Redox Potential Regulation and Intracellular Metabolite Analysis

Improving Fructose Utilization and Butanol Production by Clostridium acetobutylicum via Extracellular Redox Potential Regulation and Intracellular Metabolite Analysis
Feng-Wu Bai, Chuang Xue, You-Duo Wu, Li-Jie Chen
Jerusalem artichoke (JA) can grow well in marginal lands with high biomass yield, and thus is a potential energy crop for biorefinery. The major biomass of JA is from tubers, which contain inulin that can be easily hydrolyzed into a mixture of fructose and glucose, but fructose utilization for producing butanol as an advanced biofuel is poor compared to glucose-based ABE fermentation by Clostridium acetobutylicum. In this article, the impact of extracellular redox potential (ORP) on the process is studied using a mixture of fructose and glucose to simulate the hydrolysate of JA tubers. When the extracellular ORP is controlled above −460 mV, 13.2 g L−1 butanol is produced from 51.0 g L−1 total sugars (40.1 g L−1 fructose and 10.9 g L−1 glucose), leading to dramatically increased butanol yield and butanol/ABE ratio of 0.26 g g−1 and 0.67, respectively. Intracellular metabolite and q-PCR analysis further indicate that intracellular ATP and NADH availabilities are significantly improved together with the fructose-specific PTS expression at the lag phase, which consequently facilitate fructose transport, metabolic shift toward solventogenesis and carbon flux redistribution for butanol biosynthesis. Therefore, the extracellular ORP control can be an effective strategy to improve butanol production from fructose-based feedstock. Butanol production by Clostridium. acetobutylicum from fructose is naturally poor, and the impact of extracellular redox potential (ORP) on the process is studied using a mixture of fructose and glucose simulating the hydrolysate of JA tubers. Intracellular metabolites and RT-qPCR analysis indicate that both ATP and NADH levels are significantly improved together with upregulation of the fructose-specific PTS during the lag phase, which consequently facilitate fructose utilization, metabolic shift toward solventogenesis and carbon flux redistribution toward butanol biosynthesis.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/biot.201700198

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