[Immobilization of laccase on magnetic chitosan microspheres and study on its enzymic properties].

Laccase was immobilized on magnetic chitosan microspheres by using glutaraldehyde as cross-linking reagent. The immobilization conditions and characterization of the immobilized enzyme were investigated. immobilization conditions for laccase were: 10mL of 0.8mg/mL of laccase in phosphate buffer(0.1mol/L, pH 7.0) reacted with 50mg of magnetic chitosan microspheres at 25 degrees C for 1h and subsequently was kept at 4 degrees C for 2h. The immobilized enzyme exhibited the maximal activity at pH 3.0. The optimal temperatures for immobilized enzyme were 10 degrees C and 55 degrees C. The Km value of immobilized laccase for ABTS was 171.1 micromol/L in pH 3.0 phosphate buffer at 37 degrees C. Compared with free enzyme, the thermal, operational, and storage stabilities of the enzyme were increased after the immobilization.