Gluconic acid production by an mobilized glucose oxidase reactor with electrochemical regeneration of an artificial electron acceptor.

A reactor, using the enzymatic electrocatalysis scheme, was developed on a laboratory preparative scale for the catalytic oxidation of glucose into gluconic acid. Glucose oxidase was directly immobilized on the surface of a carbon felt electrode and a solution of glucose and benzo-quinone passed through the electrode in order to regenerate the electron acceptor. The reactor was able to produce continuously 1.5 g gluconate/h with a catalytic current of 0.4 A. This gave a high productivity ca. 100 g/h/L reactor. A one-dimensional model was developed which demonstrated the efficiency of coupling between enzymatic and electrochemical reactions due to the proximity of the two reaction sites. For example the catalytic current was practically independent of mass transfer parameters. The operational stability of immobilized glucose oxidase was increased 50 times at least when electroregenerated benzoquinone was used as oxidant instead of oxygen.