Utilization of adsorption effects for the continuous reduction of NADP+ with molecular hydrogen by Pyrococcus furiosus hydrogenase

Abstract

The use of hydrogenases for the direct reduction of cofactors with molecular hydrogen provides a means to utilize this clean and strong reducing agent for use in reductive biotransformations. The hydrogenase I from Pyrococcus furiosus is a promising enzyme for the production of NADPH from NADP⁺ with molecular hydrogen. We observed adsorption of the active enzyme by using cyclic voltammetry. Our investigations revealed an electroactive enzyme species adsorbed onto the surface of the working electrode. This facile route for immobilisation of the active enzyme was subsequently utilized for the continuous reduction of NADP⁺ to NADPH with molecular hydrogen in a continuously operated fluidized bed reactor with hydrogenase adsorbed on graphite beads. The reactor was operated at low conversion for more than 40 residence times (80 h). The apparent retention was found to be 98% on unmodified graphite carriers.