Study On Preparation Of Magnetic Fe₃O₄/PS Based Nanoparticles And Their Application In Lipase Immobilization

As a new bioengineering technology,immobilization of enzyme has greatly promoted the application of enzymes.The immobilized enzymes have been widely used in industry due to their high stability and recycling.Among varies carriers,magnetic carriers are one of the most promising platforms owing to their unique magnetic properties.This thesis summarized the progress research of synthesis of magnetic composite microspheres and their application in immobilized enzyme.Also,three kinds of novel magnetic composite carriers were fabricated,which were employed as magnetic carriers for the immobilization of lipase.The main contents for this thesis are listed as follows:1.PEG-200 modified Fe3O4 nanoparticles were synthesized by solvothermal method.Then Fe3O4 nanoparticles were modified by undecenoic acid.Fe3O4/PEG/P(St-VBC)composite microspheres were synthesized by thermal polymerization of styrene,vinylbenzyl chloride,and Fe3O4 nanoparticles in the solution.The magnetic microspheres were characterized by SEM,TEM and XRD.The magnetic composite microspheres have advantages,including small size and uniform size distribution,dispersible,superior magnetic responsibility.Lipases were immobilized on the surface of the magnetic microspheres in the phosphate buffer(0.1M,pH=8.0).The catalytic activity of the immobilized lipases was studied.It is found that thermal and pH tolerance of the immobilized lipases has been greatly enhanced.Most importantly,the immobilized lipases retain high activity after 10 times reuse.2.Oleic acid/oleylamine functionalized Fe3O4 nanoparticles were synthesized by thermal decomposition.The Fe3O4 nanoparticles exhibit spherical shape and uniform size.Magnetic Fe3O4/P(St-AA)microspheres were prepared by emulsion polymerization of styrene,acrylic acid,and Fe3O4nanoparticles in the solution containing dodecanol and sodium dodecyl sulphate.The Fe3O4/P(St-AA)composite microspheres were characterized by SEM,TEM,XRD,FT-IR,XPS and SQUID.The average diameter of the magnetic composite microspheres was found to be about 50 im.Core-shell Fe3O4/P(St-AA)nanoparticles modified with carboxylic acid groups were employed as magnetic carriers for lipases immobilization.The factors related to the catalytic activity of the immobilized lipase were systematically investigated.It is found that the enzyme's activity of the immobilized lipases has been improved.Additionally,immobilized lipases could be separated and recovered rapidly for recycling use.3.Chloromethylated Fe3O4/P(St-VBC)composite microspheres were synthesized by emulsion polymerization of styrene,vinylbenzyl chloride,and Fe304 nanoparticles in the solution containing dodecanoland sodium dodecyl sulphate.The Fe3O4/P(St-VBC)composite microspheres were characterized by SEM,TEM,XRD,FT-IR,XPS and SQUID.The composite microspheres possess uniform size and morphology,and exhibit good magnetic response.Magnetic composite microspheres were reacted with ammonia,ethylenediamine,butanediamine and hexamethylenediamine,respectively.Then magnetic microspheres were employed as magnetic carriers for lipases immobilization.The effect of the length of carbon chain on activity of the immobilized lipases was studied.And the urea tolerance,reusability and thermal stability of immobilized lipases were investigated.The stability and urea tolerance of immobilized lipases has been significantly improved compared with free lipases.Most importantly,the immobilized lipases retain high catalytic activities after 10 times' reuse.