(85g) Keynote: Cell and Process Engineering of Clostridium Acetobutylicum for Biobutanol Production

Histidine kinases in C. acetobutylicum were reported to directly control the phosphorylation state of Spo0A and the histidine kinase engineered strains showed different sporulation frequencies compared to the wild-type strain. However, very little is known about the effect of histidine kinase on metabolic regulation and solvent production. In this study, various histidine kinase genes in C. acetobutylicum were knocked-out. Compared to parental strain, the cac3319 knock-out strain produced 49% more butanol (16.4 g/L vs. 11.0 g/L), demonstrating the regulatory function of histidine kinase. The cac3319 knock-out strain still appeared rod shape and vegetative throughout the fermentation and the transcriptional analysis revealed that significantly upregulation of sol operon, which caused the mutant a hyper-butanol producing strain. Furthermore, a double knock-out strain showed further improved butanol titer of >18.0 g/L in batch fermentation and butanol titer of >20 g/L in an immobilized fermentation system. Butanol titer of >500 g/L in condensate could be achieved by two-stage gas stripping-pervaporation process integrated with ABE fermentation. In conclusion, our study demonstrated the pleiotropic regulatory effects of histidine kinases on cell differentiation and solventogenesis of histidine kinases and provided a new strategy to improve butanol production.