In recent years

laccase has been reported to be successfully immobilized on many different supports. Among them

potential applications of magnetic silica microspheres have been widely investigated for enzyme immobilization and the enzymatic stabilities can improve obviously. However

to the best of our knowledge

there is no report for the laccase immobilization on silica coated nanoparticles via one-step dopamine (DA) self-polymerization method

and nor any reports concerned with the degradation performance of paraphlorophenol (4-CP) by this immobilized laccase. In this work

the immobilized laccase on silica-coated magnetic nanoparticles were prepared through dopamine (DA) in situ entrapment

and then the immobilized laccase was applied for 4-chlorophenol (4-CP) removal. Briefly

the silica-coated magnetic nanoparticles were prepared through a sol-gel method

then the mixture of Fe3O4@SiO2 nanoparticles and DA was added to PBS (pH 6.0) containing laccase

the reaction was performed for 18 h at 25℃ with vigorous stirring

and was separated by an external magnetic field. After being washed 4 times

the product (Fe3O4@SiO2-PDA-Lac) was obtained. The scanning electron microscope images and size distribution analysis indicated that Fe3O4@SiO2 had a spherical and uniform size distribution with the average diameter of about 134 nm. The high saturation magnetization of Fe3O4@SiO2 made it easily to be separated from the reaction system. The results of X-ray diffraction (XRD) revealed that the prepared samples were Fe3O4 nanoparticles and Fe3O4@SiO2 nanoparticles. The preparing conditions of the Fe3O4@SiO2-PDA-Lac were optimized by orthogonal experiment. In the best level

the total activity recovery of the Fe3O4@SiO2-PDA-Lac can reach to 43.28%. In the degradation process

the effects of laccase concentration

solution pH and ABTS mediator on the removal efficiency of 4-CP were investigated. The results showed that when solution pH was 6 and laccase concentration was 1.2 U·ml-1

95% percentage of 4-CP was removed within 8 h enzymatic catalysis. When 50 μmol·L-1 of ABTS was added in the reaction system

the removal efficiency of 4-CP kept about 99% within 10 min enzymatic catalysis

which certified that the ABTS as a mediator could enhance the enzymatic reaction rate of the immobilized laccase. After degraded 10 times by the immobilized laccase

the removal efficiency of 4-CP still remained 67%

which exhibited an excellent reusability and operational stability.