Immobilization of laccase on magnetic nanoparticles for enhanced polymerization of phenols.

Laccase is an efficient biocatalyst for oxidative polymerization of organic substrates. However, cost of enzyme preparation, low stability and residual protein diminish the efficiency of laccase mediated polymerization. In this work, a series of silicon dioxide coated ferroferric oxide magnetic nanoparticles were modified by different functional groups including γ-methacryloxypropyltrimethoxy, succinic anhydride, glutaraldehyde and polyethylene imine. Infrared spectra indicated the magnetic carriers have been successfully modified. Vibrating sample magnetometer (VSM) analysis revealed that all of these carriers showed high magnetic responsiveness after the surface functionalization. Laccase from Cerrena sp. HYB07 was then respectively immobilized covalently on these functionalized magnetic carriers. All the immobilized laccases displayed higher thermostability than free laccase and glutaraldehyde functionalized support (named FSNG) immobilized laccase showed better performance. These immobilized laccases all showed higher efficiency than free laccase for oxidative polymerization of catechol and hydroquinone. The immobilized laccases could be separated from the water insoluble polymerization products. The polymerization product of hydroquinone by FSNG immobilized laccase showed the average polymerization degree of the poly(hydroquinone) was six (DP=6). This work provided a comprehensive exploration of laccase immobilization on magnetic carrier for catalyzing polymerization of phenols.