Preparation of chitosan-coated magnetite nanoparticles and application for immobilization of laccase

摘要

In this study, immobilization of laccase (L) enzyme on magnetite (Fe _3O_4) nanoparticles was achieved, so that the immobilized enzyme could be used repeatedly. For this purpose, Fe_3O_4 nanoparticles were coated and functionalized with chitosan (CS) and laccase from Trametes versicolor was immobilized onto chitosan-coated magnetic nanoparticles (Fe_3O_4-CS) by adsorption or covalent binding after activating the hydroxyl groups of chitosan with carbodiimide (EDAC) or cyanuric chloride (CC). For chitosan-coated magnetic nanoparticles, the thickness of CS layer was estimated as 1.0-4.8 nm by TEM, isoelectric point was detected as 6.86 by zeta (??)-potential measurements, and the saturation magnetization was determined as 25.2 emu g~(-1) by VSM, indicating that these nanoparticles were almost superparamagnetic. For free laccase and immobilized laccase systems, the optimum pH, temperature, and kinetic parameters were investigated; and the change of the activity against repeated use of the immobilized systems were examined. The results indicated that all immobilized systems retained more than 71 of their initial activity at the end of 30 batch uses.