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.