Abstract:

Mesoporous SiO₂/Fe₃O₄ hollow microspheres were used to immobilize laccase with a physical adsorption method. The influence of some experimental factors, such as adsorption time, temperature and pH value on laccase immobilization were investigated. The pH stability and temperature stability of the immobilized laccase were also studied under different conditions through researching its residual catalytic activity. The surface area(772 m²/g) and pore volume(0.83 cm³/g) of the mesoporous SiO₂/Fe₃O₄ hollow microspheres decrease to 390 m²/g and 0.66 cm³/g, respectively, after laccase was immobilized on the composite microspheres. The immobilization amount of laccase in the mesoporous silica in mesoporous SiO₂/Fe₃O₄ microspheres is 689 mg/g, which is higher than that in MCM-41(320 mg/g). The residual catalytic activities of the immobilized laccase at pH=3～6 and 60 ℃ remains higner than 80% and 60%, respectively. The immobilized laccase keeps a more stable catalytic activity than free laccase. The Michaelis constant of immobilized laccase is 1.046 mmol/L. The affinity of the immobilized laccase to its substrate declines slightly compared to free laccase. The immobilized laccase also exhibits an excellent catalytic performance in the removal of 2,4-dichlorophenol.

Key words: Mesoporous silica, Hollow magnetic microspheres, Laccase, Immobilization