Kinetic model discrimination via step-by-step experimental and computational procedure in the enzymatic oxidation of D-glucose.

The enzymatic oxidation of D-glucose to 2-keto-D-glucose (D-arabino-hexos-2-ulose, D-glucosone) is of prospective industrial interest. Pyranose oxidase (POx) from Peniphora gigantea is deactivated during the reaction. To develop a kinetic model including the main reaction and the enzyme inactivation, possible side-reactions of the non-stabilised enzyme with D-glucosone, hydrogen peroxide, and peroxide radicals were considered. A developed step-by-step combined experimental and computational procedure allowed to discriminate among alternative inactivation mechanisms and provides an increased model reliability. The most probable scheme is the enzyme inactivation by hydroxyl radicals formed from produced H2O2 in the presence of Fe2+ ions. This .OH reaction is supported by matrix assisted laser desorption ionisation-mass spectrometry (MALDI-MS) measurement. The estimated kinetic parameter values for the main reaction are of the same order of magnitude as those reported in the literature. The identified model allows a satisfactory process simulation and highlights measures to prevent the enzyme activity loss.