(177q) Engineering of Clostridium Carboxidivorans for Enhanced Ethanol and Butanol Production from Syngas and Glucose

Clostridium carboxidivorans can convert syngas (CO₂, CO, and H₂) to ethanol acetate, butanol and butyrate. 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 CO₂ 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 <0.15 g/L total acid remaining at the end of fermentation. Overexpressing fnr with adhE2 enhanced butanol production compared to only adhE2. Besides, microbial elcetrosynthesis was applied to C. carboxidivorans for enhanced solvent production in autotrophic and mixotrophic fermentations with the electrons from the cathode. This study demonstrates the potential of C. carboxidivorans as a promising host for bio-alcohol production from syngas or glucose.