Immobilization Of Laccase On The Magnetic Microspheres And Its Application In Toxic Compound Removal

In this study, magnetic nanoparticles was synthesized by a solvothermal reduction method. The magnetic nanoparticles were functionalized by chitosan, siloxane or carbon layers. Laccase were immobilized into the magnetic microspheres through the metal-chelated adsorption method, and effects of the adsorption time, the intial concentration of laccase and medium p H on the immobilization capacity were studied. In addition, the p H and thermal stabilities of immobilized laccase were studied, and the immobilized laccase was applied to remove toxic compound from water.Firstly, the preparation of chitosan magnetic microspheres with an average diameter of 3.58 μm was performed using a suspension crosslinking technique. The characterization, such as SEM, TEM, FTIR, TGA, XRD and VSM were used to intestigate the morphology and structure of the magnetic microspheres. The results indicated that the loading of laccase onto the metal-ion-chelated magnetic microspheres was approximately 100 mg/g. In comparison with free laccase, the thermal, operational and storage stabilities of the immobilized laccase were significantly improved. Immobilized laccase exhibited high removal efficiency for BPA under the combined actions of biodegradation and adsorption. Greater than 85% of BPA was removed under optimum conditions. The effects of various factors on the BPA removal efficiency of immobilized laccase were analysed. The results showed that metal-ion-chelated magnetic microspheres have great potential for industrial applications.Secondly, the functional magnetic microspheres were prepared using a hydrolytic polycondensation reaction of tetraethoxysilane with(3-Aminopropyl) triethoxysilane(APS) or with 3- Methacryloxypropyltrimethoxysilane(MPS). The results indicated that the amounts of laccase loading on the amino and acryloyl functional magnetic microspheres were approximately 130 and 150 mg/g under the optimum conditions. The stability of the immobilized laccase was highly enhanced against thermal treatments and provided better long-term storage. Compared to free laccase, the immobilized laccase exhibited significantly higher decolourisation efficiency in the degradation of a representative dye, methyl red, which resulted from the magnetic microspheres adsorption and enzymatic catalysis. These results show its great potential for industrial applications.Finally, amine-functionalized Fe3O4@C microspheres with an average diameter of 266 nm have been successfully synthesized by a solvothermal reduction method. The characterization, such as SEM, TEM, FTIR, TGA, XRD and VSM were used to intestigate the morphology and structure of the magnetic microspheres. The results indicated that the loading of laccase onto the amine-functionalized Fe3O4@C microspheres was approximately 195 mg/g. In comparison with free laccase, the thermal, p H and storage stabilities of the immobilized laccase were significantly improved. After 10 consecutive operations, the immobilized laccase retained above 60% residual activity. The removal rates of o-phenylenediamine by immobilized laccase were 88%, which were much higher than that of free laccase(50%).