Native H₂ pathways enable biocompatible hydrogenation of metabolic alkenes in bacteria

Hydrogen gas is naturally produced by microorganisms from renewable feedstocks, yet industrial hydrogenation relies almost entirely on fossil fuel-derived H₂. Despite advances in engineering biology and increasing demand for greener manufacturing, microbial H₂ has seen limited application in chemical synthesis. Here we demonstrate that genetically unmodified microorganisms can generate H₂ in situ to drive biocompatible alkene hydrogenation at the cell membrane using membrane-bound Pd catalysts. When combined with de novo alkene biosynthesis in engineered Escherichia coli, this system enables the simultaneous in vivo production of both substrate (alkene) and reagent (H₂), followed by membrane-associated biohydrogenation to yield new metabolic end products. Quantitative life cycle assessment reveals that hybrid chemo-microbial systems utilizing waste feedstocks can outperform electrolytic hydrogenation and achieve carbon-negative outcomes. Together, this work demonstrates how microbial metabolites can be generated, intercepted and metabolically multiplexed to support biocompatible transition metal catalysis and sustainable chemical synthesis in living cells. (Figure presented.)