Electrode‐driven Regioselective Oxidation of Cinnamyl Alcohol by use of Thin Biologically Active Chloroperoxidase Composite Films

AbstractWe report an electrochemical system consisting of a modified glassy carbon (GC) electrode made from chitosan (Chi), chloroperoxidase (CPO), didodecyldimethylammonium bromide (DDAB) and Nafion for the bio‐electrocatalytic oxidation of cinnamyl alcohol. The CPO‐containing composite films were characterized and qualified by SEM, AFM, and cyclic voltammetry prior to synthesis applications. The thin Chi‐DDAB‐CPO composite film modified electrode gave a pair of well‐defined, quasi‐reversible redox peaks for CPO with an electron transfer rate of 2.3 s−1. The SEM and atomic force microscopy results obtained suggest that CPO in the thin film aggregated to form island‐like structures with sizes from 300 to 1000 nm and the average film thickness was 30 nm. Unlike conventional biological systems requiring external addition of excess H2O2, a controllable amount of H2O2 was continuously generated in the electrochemical system containing the CPO modified electrode. Almost all H2O2 generated in situ was used for catalytic oxidation of cinnamyl alcohol by CPO in the composite films. In addition, the stability and the lifetime of CPO composite films were improved significantly by coating a chitosan layer on the CPO layer. The preliminary results obtained for oxidation of cinnamyl alcohol using our electrochemical system gave a total yield of 51.8 % in contrast to 7.6 % for the conventional biological system with consumption of the same amount of enzyme. The Chi‐DDAB‐CPO‐Nafion films showed a total turnover number [molproduct molenzyme catalyst−1 (TTN)] of 80 500, 5‐fold more than those reported for oxidation of primary alcohols.