Overcoming the Gas–Liquid Mass Transfer of Oxygen by Coupling Photosynthetic Water Oxidation with Biocatalytic Oxyfunctionalization

Gas-liquid mass transfer of gaseous reactants is a major limitation for high space-time yields, especially for O2 -dependent (bio)catalytic reactions in aqueous solutions. Herein, oxygenic photosynthesis was used for homogeneous O2 supply via in situ generation in the liquid phase to overcome this limitation. The phototrophic cyanobacterium Synechocystis sp. PCC6803 was engineered to synthesize the alkane monooxygenase AlkBGT from Pseudomonas putida GPo1. With light, but without external addition of O2 , the chemo- and regioselective hydroxylation of nonanoic acid methyl ester to ω-hydroxynonanoic acid methyl ester was driven by O2 generated through photosynthetic water oxidation. Photosynthesis also delivered the necessary reduction equivalents to regenerate the Fe2+ center in AlkB for oxygen transfer to the terminal methyl group. The in situ coupling of oxygenic photosynthesis to O2 -transferring enzymes now enables the design of fast hydrocarbon oxyfunctionalization reactions.