Adapting Gas Fermenting Bacteria for Light-driven Domino Valorization of CO2

We report the adaptive laboratory evolution (ALE) of Clostridium ljungdahlii (Cl) for enhanced syngas fermentation, enabling its integration into a photocatalytic CO₂-to-syngas conversion system for the upcycling of CO₂ to C₂ products, acetate and ethanol. The adapted strain, Cladapt, exhibits a 2.5-fold increase in growth rate and a 120-fold enhancement in C₂ production compared to the wild-type (Clwt). Isotopic labeling confirmed Cladapt's high conversion efficiency, yielding 6:1 and 9:1 ratios of ¹³C:¹²C in acetate and ethanol, respectively. Whole genome sequencing revealed eight unique mutations in Cladapt, whereas RNA-seq identified significant alterations in gene expression, shedding light on its enhanced metabolism. Coupling Cladapt with a CO₂-to-syngas converting semiconductor-molecule hybrid photocatalyst, TiO₂|phosphonated Co(terpyridine)₂, enabled the assembly of a photocatalytic domino system for CO2-to-syngas-to-C2 conversion. This study offers a streamlined approach to improving syngas fermentation in Cl, insights into microbial adaptability, and an ALE-guided pathway for solar-powered CO₂ upcycling using an inorganic-bacterial cascade strategy.