Abstract
The solar-driven valorization of CO(2) to fuels and chemicals provides an exciting opportunity to develop a circular chemical industry, but the controlled production of multicarbon organics remains a major challenge. Here, we present an abiotic-biotic domino strategy that integrates a photocatalytic CO(2)-to-syngas conversion system with evolved syngas-fermenting bacteria to enable the upcycling of CO(2) into valuable C(2) products, including acetate and ethanol. To optimize microbial syngas fermentation through an accessible and chemist-friendly platform, we employ adaptive laboratory evolution (ALE) of Clostridium ljungdahlii (Cl). The adapted strain, Cl (adapt), exhibits a 2.5-fold increase in growth rate and a 120-fold enhancement in C(2) production compared to the wild type (Cl (wt)). Isotopic labeling confirmed Cl (adapt)'s high conversion efficiency, yielding 6 : 1 and 9 : 1 ratios of (13)C : (12)C in acetate and ethanol, respectively. Whole genome sequencing revealed mutations in Cl (adapt), offering initial clues to its enhanced metabolism. A scaled-up semiconductor-molecule hybrid photocatalyst, TiO(2)|phosphonated Co(terpyridine)(2), was employed to generate sufficient syngas (CO/H(2) ratio: ∼30 : 70 with 1.3 mmol of CO after 6 days) for Cl (adapt) to demonstrate photocatalytic CO(2) → syngas → C(2) conversion (yielding 0.46 ± 0.07 mM, or 3.2 μmol, of acetate). This study offers a streamlined approach to improving syngas fermentation in Cl, insights into microbial adaptability, and an ALE-guided pathway for solar-powered CO(2) upcycling using an inorganic-microbial domino strategy.