Study Of Immobilized Enzyme Based On Magnetic Nanoparticles

Enzyme is a kind of biological macromolecules with catalytic ability and is widely found in nature. Catalysis by enzyme has been proved to offer lots of special features, such as mild reaction conditions (biological pH and temperature), biodegradation, high catalytic efficiency and strong specificity. During the past few decades, study on the immobilization technology and enzyme carriers has attracted a lot of researchers'attention, because the free enzyme is unstable and can not be reused and recycled. The principle of immobilized enzyme is to immobilize the enzyme onto a special carrier to keep it in a defined space through some processes and the enzyme can still retain the catalytic ability.Magnetic nanoparticles have been widely applied in biology, medicine and environment fields due to their unique superparamagnetism and good biocompatibility. Enzyme immobilized onto magnetic nanoparticles can be separated from the solution quickly under an external magnetic field. Another advantage of magnetic nanoparticles as enzyme carriers is their large surface area and thus can provide more binding sites for enzyme immobilization.In this paper, enzyme immobilization on magnetic nanoparticles in different methods was investigated. For the first method, water-soluble magnetic Fe₃O₄ nanoparticles were firstly synthesized by a co-precipitation method. Then lipase and magnetic nanoparticles were co-entrapped in calcium alginate capsules and several factors affecting the enzyme recovery activities were studied. For the second method, magnetic Fe₃O₄ nanoparticles were modified with amino silane in ethanol and acetone respectively to produce amino groups on the surface. Then alkaline protease was covalently coupled to these amino-modified magnetic nanoparticles. Comparing their reproducibility and operational stability, the immobilized enzyme with good performance was chosen for biocatalysis in the microwave.