In this study,cage-like mesoporous silica was used as the carrier to immobilize laccase by a physical approach,followed by encapsulating with chitosan/alginate microcapsule membranes to form microcapsules of immobilized laccase based on layer-by-layer technology.The relationship between laccase activity recovery/leakage rate and the coating thickness was simultaneously investigated.Because the microcapsule layers have a substantial network of pores,they act as semipermeable membranes,while the laccase immobilized inside the microcapsules acts as a processing plant for degradation of2,4-dichlorophenol.The microcapsules of immobilized laccase were able to degrade 2,4-dichlorophenol within a wide range of 2,4-dichlorophenol concentration,temperature and p H,with mean degradation rate around 62%.Under the optimal conditions,the thermal stability and reusability of immobilized laccase were shown to be improved significantly,as the removal rate and degradation rate remained over 40.2% and 33.8% respectively after 6 cycles of operation.Using mass spectrometry（MS） and nuclear magnetic resonance（NMR）,diisobutyl phthalate and dibutyl phthalate were identified as the products of 2,4-dichlorophenol degradation by the microcapsules of immobilized laccase and laccase immobilized by a physical approach,respectively,further demonstrating the degradation mechanism of 2,4-dichlorophenol by microcapsule-immobilized laccase.
Junya YangYan HuangYuxiang YangHongming YuanXiangnong Liu
In this paper, the laccase immobilized on Fe304@SiO2-NH2 nanoparticles was successfully prepared by the glutaraldehyde cross-linking method. The degradations of 2,4-diehlorophenol （2,4-DCP） catalyzed by laccase and immobilized laccase were carried out. The optimal conditions regarding degradation efficiency were also discussed, which include reaction time, pH value, temperature, concentration of 2,4-DCP and laccase. When laccase was immobilized on Fe304@SiO2-NH2 carrier by crosslinking with glutaraldehyde, the stability and repetition were im- proved significantly. The removal efficiency of 2,4-DCP by immobilized laccase still remained over 59% after six cycles of operation. Degradation of 2,4-DCP is a first-order reaction and the activation energies of 2,4-DCP catalyzed by laccase and immobilized laccase are 51.93 kJ·mol-1 strate the immobilized laccase had a faster degradation Fe304@MSS-NH2 can promote the degradation reaction. and 44.12 kJ·mol-1, respectively. The results demonrate than the free laccase; the magnetic carrier
With the Fe3O4@MSS(magnetic mesoporous silica spheres)–NH2as the carrier and the glutaraldehyde as crosslinking agent,the immobilized laccase has been prepared and characterized by XRD,IR,SEM and BET etc.Under the optimal conditions,the removal efficiency of2,4-DCP reached 88%and the removal efficiency still remained 61.5%after five cycles of operations.In virtue of GC–MS analysis,2,5-dimethoxyl-1,4-quinone,2-chlorine-1,4-dimethoxyl benzene,3,30-dichlorine-4,40-dimethoxyl biphenyl,maleic acid phenol ester,and three kinds of maleic acid,alcohol ester,and para-hydroxyl phenol ester compounds have been identified as intermediate and final degradation products of 2,4-DCP,respectively.Besides,the degradation products of 2,4-DCP have been confirmed by performing the1H-NMR and13C-NMR experiments,further demonstrating the degradation mechanism of 2,4-DCP by the immobilized laccase.
Yan HuangYanjie XiYuxiang YangCheng ChenHongming YuanXiangnong Liu
