Effect of metal nanoparticles on electrochemical regeneration of cofactor for redox enzymatic reactions

Abstract

Redox biocatalysts can accelerate many valuable reactions for the synthesis of high-valued, fine compounds, which can not be accomplished by conventional chemical catalysts. Those biocatalysts or oxidoreductases critically require cofactors such as NAD(P)H for the redox reactions. Due to the economical infeasibility of stoichiometric use of cofactors, their regeneration is a key issue for their application to redox reactions. Among many approaches for the regeneration of cofactors, electrochemical method has advantages over enzymatic method because of simple and clean characteristics enabling no addition of electron donor or acceptor, no by-product. However, the electrochemical method suffers from its low efficiency arising from the short-range electron transfer that occurs only between electrode surface and cofactors. In this thesis study, it has been found that the low rate of electrochemical reduction of cofactors can be greatly enhanced by the presence of metal nanoparticles, especially platinum. The increased reduction rate was dependant on the concentration of nanoparticles and the stirring rate of reaction medium. The mechanism of catalytic activity of platinum nanoparticle was studied by cyclic voltammetry. Further, enzymatic synthesis of glutamate coupled with the electrochemical regeneration of NADH was successfully accomplished, resulting continuous conversion of reaction substrate proportional to the concentration of platinum nanoparticle.