(177r) N-Butanol Production in Clostridium Tyrobutyricum Triggered By Overexpression of Hydrogenase

Clostridium tyrobutyricum was found a promising host for n-butanol production with metabolic engineering. Various enzymes have been introduced into C. tyrobutyricum for improved n-butanol production. In this study, a hydrogenase from Ethanoligenens harbinense was overexpressed in C. tyrobutyricum and unexpected n-butanol synthesis was triggered. In glucose fermentation, Strains overexpressing hydrogenase (Ct-Hyd2293) produced 2.5 g/L butanol while the parental strain (Ct-WT) did not produce butanol. Compared to Ct-WT, Ct-Hyd2293 produced ~55% more ethanol along with ~34% less butyrate and ~11% less hydrogen. Biomass of Ct-Hyd2293 decreased 35% compared with the wild type strain. Enzyme activity assay showed that the activities of hydrogenase and butanol dehydrogenase both significantly increased after hydrogenase overexpression. More carbon flux shifted to C2 pathways as C4/C2 ratio decreased ~42% in Ct-Hyd2293. The increase in ethanol and butanol production indicated the overexpression of hydrogenase redistributed the metabolic network of C. tyrobutyricum from acidogenesis to solventogenesis. This study provided a novel direction of metabolic engineering for n-butanol production.