Degradation Of MXC Catalyzed By Immobilized Laccase With Tubular Mesoporous Materials

Laccase, as a common biocatalyst, has been widely applied with high catalytic efficiency, substrate specificity and high selectivity. However, the free laccase has poor stability and are vulnerable to the external environment to inactivation, difficult to separate from the reaction medium, which limit the reuse of the laccase. The immobilized laccase can not only improve the thermal stability and pH stability of laccase, but also can be easily recoverd and reused, improving the efficiency of laccase and reducing the cost. Therefore, the immobilized laccase has a broad application prospects in biological engineering field, chemical, environmental protection.Compared with other materials in immobilized laccase field, tubular mesoporous silica materials have a large specific surface area, an adjustable pore size and good biocompatibility, etc, making it possible to be used as the excellent carrier of the immobilized laccase, which is suitable for the immobilization and separation of enzymes, proteins and other biological macromolecules. Besides, through doping modification on pure mesoporous materials, more excellent carriers with high activity and improved catalytic efficiency can be prepared, which makes it become a hot field of biocatalysis.In this thesis, Firstly, under alkaline conditions, by using the pre-synthesized needle-like nano CaCO3as the hard template, CTAB as structure-directing agent, TEOS as a silicon source, tubular mesoporous SiO2and tubular mesoporous Si-Fe were prepared and then were characterized by X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), Infrared Radiation (IR), Vibrating Sample Magnetometer (VSM), which all showed good results. Secondly, by using the tubular mesoporous Si-Fe material and the tubular mesoporous SiO2as the carrier respectively, the optimum conditions of the immobilized enzyme and the degradation of the immobilized enzyme to pesticides MXC were studied. The results showed that in the conditions while at room temperature,0.1g of the tubular mesoporous Si-Fe material,5mL of pre-configured Fe3O4/AOT/hexane mixture, and0.11mL pH5.5NaAc-HAc buffer, shaking for8h, air-dried at room temperature,5mL of6%glutaraldehyde solution, shaking8h, the immobilized enzyme with the maximum activity could be obtained. During the degradation of MXC by laccase immobilized on the tubular mesoporous SiO2, when MXC concentration was25mg/L, the concentration of the surfactant AOT was4g/L, the pH value was5.5, the oscillation time was10h, temperature was45℃, the degradation rate was the best, which could reach the maximum of40%. The activation energy of the MXC degradation by immobilized enzyme was about41.46kJ/mol. The MXC degradation rate remained about20%after recycling for seven times. On this basis, in order to comparing with the former, the degradation effect of MXC by laccase immobilized on tubular mesoporous Si-Fe were also researched, the results showed that the latter had more efficiency on the MXC degradation. Besides, by using GC-MS method, degradation products of MXC catalyzed by immobilized laccase were measured and the reaction mechanism were inferred initially.