Oxidation of Indole with CPO and GOx Immobilized on SBA-15

In recent years, enzymatic oxidations are being evaluated for production of fine chemicals and pharmaceuticals. For industrial applications, heterogeneous biocatalysts are favored for several reasons, e.g. easy separation and recycling of the catalyst. In the present work, chloroperoxidase (CPO) from Caldariomyces fumago was immobilized on the mesoporous molecular sieve SBA-15 and tested in the oxidation of indole to 2-oxindole using hydrogen peroxide as oxidant. The deactivation of peroxidases by external addition of peroxides was circumvented by in-situ hydrogen peroxide generation. H2O2 was produced by glucose oxidation with glucose oxidase (GOx) from Aspergillus niger immobilized on SBA-15. By the use of this tandem reaction, CPO deactivation was largely suppressed due to the “sensitive” hydrogen peroxide generation. Beside deactivation, leaching of the enzymes is a frequently encountered problem. In order to avoid leaching from the mesoporous support, chloroperoxidase (CPO) and glucose oxidase (GOx) were covalently anchored to the carrier surface via chemical bonding. We have observed that under continuous operation in a fixed-bed reactor leaching of the covalently anchored enzymes is significantly reduced as compared to catalysts containing physically adsorbed enzymes.