Immobilization of laccase on amine-terminated magnetic nano-composite by glutaraldehyde crosslinking method
(1.Key Laboratory of Silicate Materials Science and Engineering, Wuhan University of Technology, Ministry of Education, Wuhan 430070, China2.Key Laboratory of Fiber Optic Sensing Technology and Information Processing, Ministry of Education, Wuhan University of Technology, Wuhan 430070, China)
Abstract: The immobilizing procedure has great influence on the activity of the immobilized laccase. The laccase was immobilized on copper tetraaminophthalocyanine (CuTAPc)-Fe3O4 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 ℃ and 2 h, respectively. The average diameter of the immobilized laccase is 78 nm, the saturation magnetization (Ms) of the immobilize laccase is 23.45 A？m2/kg and the surface area of the immobilized laccase is 115.03 m2/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(Km) of the immobilized laccase is 2.38×10？5 mol/L.
Key words: immobilization; laccase; glutaraldehyde; copper tetraaminophthalocyanine-Fe3O4; activity