Immobilization Of Lactase On Modified Chitosan Magnetic Micropheresc

Magnetic polymer microsphere is a novel functional material which has the properties of magnetic ressponsivity and the reactivity of the function groups. As the carrier of enzyme, cell and drug, it is widely applied in many fields, such as bio-engineering, cytology, biomedicalscience and so on. In this paper, chitosan magnetic microspheres were prepared and modified. Lactase was immobilized on modified magnetic chitosan microspheres. Immobilized lactase can be repetitive-used. Not only the consumption of enzyme was reduced, but also automation management becomes possible.The main experiments and conclutions of this paper were described as follows:(1) Magnetic fluid was synthesized by chemical co-precipitation. When n(Fe2+):n(Fe3+) was 1:2, reactive temperature was 60℃, ripening temperature was 85℃, pH was 11, reaction time was 1.5 h, the magnetic fluid with high magnetism and small diameter can be obtained.Characterized the sample with XRD,TEM,VSM and nano particle analyzer. It was indicated that the as-synthesized magnetic fluid was Fe3O4 with an average size of 20nm. The saturated magnetization of the magnetic fluid was 67.3emu/g at room tempareture.(2) Modified chitosan magnetic microspheres were prepared with reversed-phase suspension polymerization method using HEMA and GMA as monomers and ammonium persulfate as initiator. Research the preparation and optimum condition to obtain a kind of excellent carrier. When oil-water ratio was 0.25, concentration of chitosan was 2%, adding 6mL span-80, chitosan/Fe3O4 was 3/1, it was found that as-synthesized carried have good characteristics.The prepared magnetic microspheres were characterized by FT-IR, SEM, optical microscopy, TEM, laser particle size analysis and VSM. The results indicated that modified chitosan magnetic microspheres presented a regular spherical shape with poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) grafted onto the chitosan layer that coated outside the Fe3O4 cores due to the electrostatic interaction. The average diameter of the magnetic microspheres was 10.67μm within a narrow size distribution of 6.6-17.4μm. The saturation magnetization and the retentivity of the magnetic microspheres was 7.0033 emu/g. TGA showed that Fe3O4 contents was about 30.75%.(3) Lactase was immobilized on modified chitosan magnetic microspheres by adsorption, covalent bonding and cross-linking with glutaraldehyde. The optimum conditions of lactase immobilization were ascertained:After the resuted carriers were swelled sufficiently in 0.25M pH7.0 phosphate buffer,2.0U/mg lactase was added to and kept at 4℃for 3h, then reacted with 0.1% glutaraldehyde for 4h. The activity of immobilized lactase was 685U/g, and the activity recovery was 48.18%. Compared with free enzyme, the pH and thermal stability of immobilized lactase were increased. After 10 cycles continuous operation, the immobilized lactase activity was kept in 70 % above.