Electrochemically Enhanced Biosynthesis of Gluconic Acid

Overview & Synopsis

A bioelectrochemical interface was designed by entrapping glucose oxidase (GOx) in a polypyrrole film electrosynthesized on a platinum electrode. The efficiency of the modified electrodes for synthesis was evaluated with the reaction of glucose oxidation into gluconic acid by oxygen. Glucose transformation was carried out with or without the electrochemical step. The electrochemical step led to the regeneration of oxygen, which also ensured the oxidation of the hydrogen peroxide produced as a by-product, thus protecting GOx against denaturing. The experimental results were first analyzed according to the “effectiveness factor/Thiele modulus” classic approach. They were confirmed theoretically by a model based on the resolution of glucose mass balance equation. Second, the simulation of the concentration profiles of oxygen and hydrogen peroxide inside the polymer film explained the experimental data, highlighting the protection of the enzyme by the electrochemical step. The maximum conversion yield was obtained with a 500-nm-thick polymer. As a consequence of the combined effects of oxygen regeneration and enzyme protection, the electrochemical step increased by a factor of 2 the transformation ratios obtained with immobilized GOx. Furthermore, the electrochemically enhanced process was 50% more efficient than the equivalent homogeneous process carried out for 24 h with the same amount of enzyme.