Zirconia supported gold–palladium nanocatalyst for NAD(P)H regeneration via two-step mechanism

The regeneration cycle of expensive cofactor, NAD(P)H, is of paramount importance for the bio-catalyzed redox reactions. Here a ZrO2supported bimetallic nanocatalyst of gold-palladium (Au-Pd/ZrO2) was prepared to catalyze the regeneration of NAD(P)H without using electron mediators and extra energy input. Over 98% of regeneration efficiency can be achieved catlyzed by Au-Pd/ZrO2using TEOA as the electron donor. Mechanism study showed that the regeneration of NAD(P)H took place through a two-step process: Au-Pd/ZrO2nanocatalyst first catalyzed the oxidation of triethanolamine (TEOA) to glycolaldehyde (GA), then the generated GA induced the non-catalytic reducing of NAD(P)+to NAD(P)H under an alkaline environment maintained by TEOA. This two-step mechanism enables the decoupling of the regeneration of NAD(P)H in space and time into a catalytic oxidation and non-catalytic reducing cascade process which has been further verified using a variety of electron donors. The application significance of this procedure is further demonstrated both by the favorable stability of Au-Pd/ZrO2nanocatalyst in 5 successive cycles preserving over 90% of its original activity, and by the excellent performance of the regenerated NADH as the cofactor in the catalytic hydrogenation of acetaldehyde using an ethanol dehydrogenase.