Immobilization of laccase on amine-terminated magnetic nano-composite by glutaraldehyde crosslinking method

Abstract

The immobilizing procedure has great influence on the activity of the immobilized laccase. The laccase was immobilized on copper tetraaminophthalocyanine (CuTAPc)-Fe 3O 4 magnetic nano-composite by glutaraldehyde crosslinking method via a two-step reaction. For 1 g nano-composite, the optimum pH value, the quantity, the concentration and reaction time of glutaraldehyde are 7.0, 10 mL, 10% and 4 h, respectively. In the second step the optimum pH value, reaction temperature and reaction time of laccase are 5.0, 0 °C and 2 h, respectively. The average diameter of the immobilized laccase is 78 nm, the saturation magnetization ( M s) of the immobilize laccase is 23.45 A·m 2/kg and the surface area of the immobilized laccase is 115.03 m 2/g. When 2.0 mg/mL laccase solution is used under optimum conditions and 2, 2′-azino-bis-(3-ethylbenzothiazoling-6-sulphonic acid) is used as substrate, the activity of immobilized laccase reaches 1 430 U/g (nano-composite) and the Michealis-Menten constant( K m ) of the immobilized laccase is 2.38×10 −5 mol/L.