Immobilized Process And Stability Of PPL Assembled On SBA-15 Mesoporous Materials: Effects Of Physical And Chemical Micro-Environment

SBA-15, as the high surface area, large pores and abundant hydroxyl groups on the surface of mesoporous material, is used as the support for immobilization of porcine pancreatic lipase (PPL). This dissertation focuses on the effect of micro-environment on the immobilizing process and stability of PPL assembled on SBA-15 mesoporous material.Highly ordered hexagonal mesoporous material SBA-15 with different pore sizes was prepared via two methods: Under different crystallization temperatures synthesis and by the addition of co-solvent organic molecules 1, 3, 5-trimethylbenzene (TMB), using nonionic triblock P123 as template. It was found that SBA-15 had more ordered hexagonal pores under different crystallization temperature than adding TMB to expand the pore sizes of the SBA-15. Two functionalized SBA-15-type molecular sieves with dimethoxy silane (DM), diisopropyl dimethoxy silane (DIP), respectively, were prepared by siloxypropane tethers to the siliceous surface of SBA-15 via in situ synthesis, which the siliceous surface of SBA-15 have been alkylized with different degree hydrophobicity.Porcine pancreatic lipase (PPL) has been successfully immobilized in the mesoporous channels of SBA-15 with different pore size and different surface characters. Three kinetic models viz. the pseudo-first order, the pseudo-second order and the intraparticle diffusion models were used to simulate the experimental data. It was found that the pseudo-first order kinetic model can not be used to the adsorption process. The pseudo-second order kinetic model could be used to describe the adsorption process most satisfactorily. The intrapartic diffusion was present, but not the only rate-controlling step. In order to study the hindered diffusion, a continuity equation for a protein in cylindrical pore was adopted. The smaller pore diameter or alkane functionalized inner surface of the SBA-15 as hosts for enzyme immobilization has significant effects on the internal diffusion. Diffusion function weakened while the adsorption effects of PPL on inner surface became more and more distinct combined with the enlarging pore diameters.Comparing with purely siliceous SBA-15, the functionalized SBA-15 has more efficiency in the enzyme immobilization. The characters of the immobilized enzyme were also studied and compared with free enzyme. The results show that the optimum temperature of PPL is increased after immobilization; and the stabilities of the immobilized enzyme of pH value were lower than free enzyme, however, the thermostability and storedstability were obviously higher.