Immobilization Of Lactase On Modified Chitosan Magnetic Microspheres

Magnetic polymer microspheres, as a kind of novel functional polymer material, which has magnetism, it is a kind of organic-inorganic compound nanoparticle that can be easily separated and oriented under applied magnetic field. it can be widely applied in many fields, such as bioengineering, cytology, biomedical science and so on.The Combination of polymer chitosan and modified magnetic nanoparticles for the preparation of modified magnetic chitosan microspheres that have attracted considerable attention as they display very important significance and value in aspects. For example, they can be applied as carrier of biomacromolecules and cells because of functional -NH2 and -OH of chitosan encapsulating magnetic particles. And owing to the magnetism of the microspheres, separation efficiency is increased in the presence of outer magnetic field, in this paper, magnetic fluid was synthesized by chemical co-precipitation.Combined with chitosan modified to the preparation of modified chitosan microsphere immobilized enzyme lactase.The main experiments and conclutions of this paper were described as follows:Fe₃O₄ magnet fluid was synthesized by the chemical co-precipitation, using FeCl2, FeCl3 and NaOH. When n（Fe2+）:n（Fe3+）=1:1.5, pH was 9, reactive temperature was 45℃, ripening temperature was 80℃,30mL of 10% PEG, Fe3O4 with a strong magnetic was obtained. Sodium oleate was carried out on the liquid surface modification, and the optimal condition of pH modification, modification temperature, dosage of sodium oleate and reaction time was determined through single factor design and the optimum experimental conditions as follows:pH was 6.0, modification temperature was 80℃, the amount of modifier was 25mL, and reaction time was 25min, the change was the best, the stability of the obtained nanoparticles were strongest.Magnetic chitosan microspheres （M-CS） were prepared by reverse phase suspension process using Fe3O4 as core, paraffin as dispersed medium, Span-80 as emulsifier, and glutaraldehyde as cross-linking agent, The results showed that when the amount of dispersant was 16mL, the dispersion effect was best, when the concentration of chitson was 0.03g/mL, the amount of glutaraldehyde was 11mL, stirring speed was 1200r/min, we obtained modified magnetic chitosan microspheres with a strong magnetic response.Lactase was immobilized on modified chitosan magnetic microspheres covalent bonding and cross-linking with glutaraldehyde. The optimum lactase immobilization were ascertained:the amount of the crosslinking agent was 1.0mL, crosslinking temperature was 30℃, immobilization time was 22h, and fixed temperature was 20℃, we got the immobilized enzyme with highest recoveries.