Chemo-Bio Catalysis Using Carbon Supports: Application In H-2-Driven Cofactor Recycling

Heterogeneous biocatalytic hydrogenation is an attractive strategy for clean, enantioselective C=X reduction. This approach relies on enzymes powered by H-2-driven NADH recycling. Commercially available carbon-supported metal (metal/C) catalysts are investigated here for direct H-2-driven NAD(+) reduction. Selected metal/C catalysts are then used for H-2 oxidation with electrons transferred via the conductive carbon support material to an adsorbed enzyme for NAD(+) reduction. These chemo-bio catalysts show improved activity and selectivity for generating bioactive NADH under ambient reaction conditions compared to metal/C catalysts. The metal/C catalysts and carbon support materials (all activated carbon or carbon black) are characterised to probe which properties potentially influence catalyst activity. The optimised chemo-bio catalysts are then used to supply NADH to an alcohol dehydrogenase for enantioselective (>99% ee) ketone reductions, leading to high cofactor turnover numbers and Pd and NAD(+) reductase activities of 441 h(-1) and 2347 h(-1), respectively. This method demonstrates a new way of combining chemo- and biocatalysis on carbon supports, highlighted here for selective hydrogenation reactions.