Efficient bioelectrocatalytic NADH regeneration with a novel amino-functionalized viologen redox polymer

Oxidoreductase enzymes, used for a variety of applications including organic synthesis and pharmaceutical industry, require reduced nicotinamide adenine dinucleotide (NADH) as reducing equivalents. Methods for regenerating NAD⁺ to NADH are of significant interest due to the high cost and stoichiometric amounts of cofactor required. Diaphorase/redox mediator systems have shown promise for this purpose, but suitable mediators are few due to the low redox potential required, necessary downstream processing and stability issues. A novel amino-functionalized viologen is presented in this work which, upon immobilization with diaphorase, yields bioactive NADH with high selectivity (99 %) and faradaic efficiency (99 %). This system was tested with NADH-dependent formate dehydrogenase, showing a 21-fold improvement in formate yield compared to an enzymatic negative control without NADH regeneration. The findings underscore the potential of this novel amino-functionalized viologen polymer to advance sustainable and efficient NADH regeneration at very low overpotential.