Engineering of Microbial Cell Factories for Enhanced Acetic Acid and Ethanol Production Via Heterologous Overexpression of the CODH Gene in CO Fermentation.

This study evaluates the performance of carbon monoxide dehydrogenase ()-embedded strains in bench-scale microbial electrochemical systems (MES) for CO reduction to biofuels and biochemicals. CO fermentation efficiency was evaluated by comparing the wild-type (Wild), a negative control strain lacking the gene (NC-BL21), and engineered strain (Eng) alone and with IPTG induction (Eng+IPTG). Four electrochemical systems were used, viz. Wild+E, NC-BL21+E, Eng+E, and Eng+IPTG+E, with a poised potential of -0.6 V applied to the working electrode. CO and bicarbonate were supplemented to a total inorganic carbon (IC) concentration of 40 g/L, with a retention time of 60 h. The engineered strain demonstrated enhanced metabolic performance compared to the wild-type and negative control strains, yielding maximum formic acid (2.1 g/L) and acetic acid (9.3 g/L) under the Eng+IPTG+E condition. Solventogenesis also influenced positively in the same system with the ethanol yield of 3.9 g/L, substantially exceeding biochemicals yield observed in the wild-type strain (2.4 g/L, acetic acid). The engineered strains exhibited superior cumulative yields (0.40 g/g), enhanced CODH-mediated charge flux stability (60 vs 5 in the wild type), and upregulated expression of key genes in the Wood-Ljungdahl pathway (WLP). Bioelectrochemical performance analysis demonstrated elevated reductive catalytic currents, enhanced CO reduction, and optimal charge transfer kinetics. This study highlights the synergistic potential of genetic engineering, specifically CODH overexpression, combined with electro-fermentation for enhanced biofuel and biochemical production from C1 gases.