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.