Metabolic engineering of Clostridium carboxidivorans for enhanced ethanol and butanol production from syngas and glucose

Abstract Clostridium carboxidivorans can convert CO 2 , CO and H 2 to ethanol and n -butanol; however, its industrial application is limited by the lack of tools for metabolic pathway engineering. In this study, C. carboxidivorans was successfully engineered to overexpress aor , adhE2 , and fnr together with adhE2 or aor . In glucose fermentation, all engineered strains showed higher alcohol yields compared to the wild-type. Strains overexpressing aor showed CO 2 re-assimilation during heterotrophic growth. In syngas fermentation, compared to the wild-type, the strain overexpressing adhE2 produced ∼50% more ethanol and the strain overexpressing adhE2 and fnr produced ∼18% more butanol and ∼22% more ethanol. Interestingly, both strains showed obvious acid re-assimilation, with fnr with adhE2 enhanced butanol production compared to only adhE2 . This is the first report of overexpressing homologous and heterologous genes in C. carboxidivorans for enhancing alcohols production from syngas and glucose.