Efficient NADH Regeneration by a Redox Polymer-Immobilized Enzymatic System

Given the high costs and stoichiometric amounts of reduced nicotinamide adenine dinucleotide (NADH) required by the many oxidoreductases used for organic synthesis and the pharmaceutical industry, there is a need for the efficient reductive regeneration of NADH from its oxidized form, NAD+. Bioelectrocatalytic methods for NADH regeneration involving diaphorase and a redox mediator have shown promise; however, strong reductive mediators needed for this system are scarce, generally unstable, and require downstream separation. The immobilization of diaphorase in cobaltocene-modified poly(allylamine) redox polymer is presented which is capable of producing bioactive 1,4-NADH with yields between 97% and 100%, faradaic efficiencies between 78% and 99%, and turnover frequencies between 2091 h–1 and 3680 h–1 over a range of temperatures spanning 20 to 60 °C. By using this system, methanol and propanol production by an NADH-dependent alcohol dehydrogenase were enhanced 7.1- and 5.2-fold, respectively, compared with a negative control. Finally, the efficiency of this approach coupled with its high operational stability (91% of the maximum activity after five experimental cycles) renders it among the most promising means of NADH regeneration yet developed.