Bio-Photocatalytic Synergy Enables Valorization of CH₄ and CO₂ Into Hydrogen and 4-Hydroxybenzoate in Engineered Methanotrophic Bacteria

Valorization of decentralized one-carbon chain (C₁) resources into value-added products has garnered significant attention, owing to its dual benefits in resource recovery and carbon mitigation. To address the challenge of co-converting methane (CH₄) and carbon dioxide (CO₂), we developed a solar-driven biohybrid system that synergistically integrates biosynthesis and photocatalysis. The core of this system relies on a genetically engineered methanotrophic cell factory and newly designed biocompatible photocatalytic metal complexes. The methanotrophic bacteria utilize CH₄ as the primary feedstock to biosynthesize 4-hydroxybenzoate (4HBA) while realizing CO₂ sequestration. The photocatalytic metal complexes, meanwhile, capture formate (a metabolic byproduct of cells) to generate hydrogen (H₂) and photoelectrons—with the latter directly supplying reducing power to support cellular activities in genetically tailored cells. Under optimal conditions, this solar-driven system achieved a 4HBA titer of 472.36 µg/L, a H₂ yield of 0.59 mmol H₂/mol CH₄, and over 50% reduction in carbon emissions. The study not only establishes a feasible biomanufacturing strategy for the upcycling of C₁ gaseous feedstocks but also highlights the potential of integrating biological and photochemical technologies to advance sustainable energy and environmental solutions.