Abstract
BackgroundLaccase, a multicopper oxidase that catalyzes the oxidation of phenols, aromatic amines, and benzenethiols, has attracted much attention in applications of organic synthesis, bioremediation, and pulp/textile bleaching. However, free laccases cannot be recycled and are easily inactivated in diverse environmental conditions. Enzyme immobilization is a promising strategy to improve stability, resistance to extreme conditions, and reusability of laccase.ResultsIn this study, amino-functionalized magnetic Fe3O4 nanoparticles were synthesized for co-immobilization of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and laccase by glutaraldehyde cross-linking method. The magnetic nanoparticles were characterized with FTIR, XRD and VSM. Cyclic voltammetry was carried out to verify electrochemical behaviors of the co-immobilized laccase and TEMPO nanoparticles. When the co-immobilized laccase and TEMPO nanoparticles were used to decolorize acid fuchsin, the maximum decolorization rate of 77.41% was obtained with the ratio of TEMPO to laccase being 0.3 mM/g:120 U/g.ConclusionThe co-immobilized nanoparticles retained above 50% residual activity after eight cycles of operation, which presented an approach to develop a co-immobilized laccase and mediator system for potential industrial application.
Highlights
Laccase, a multicopper oxidase that catalyzes the oxidation of phenols, aromatic amines, and benzenethiols, has attracted much attention in applications of organic synthesis, bioremediation, and pulp/textile bleaching
This can be overcome by establishing laccase mediator system (LMS) (Jeon and Chang 2013; Mogharabi and Faramarzi 2014). 2,2′-Azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), 1-hydroxybenzo-triazole (HBT), and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) are usually used as mediators to transfer electrons from substrate to laccase
Decolorization of acid fuchsin The reaction cycle catalyzed by the co-immobilized laccase and TEMPO is shown in Scheme 2
Summary
Amino-functionalized magnetic Fe3O4 nanoparticles were synthesized for co-immobilization of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and laccase by glutaraldehyde cross-linking method. The magnetic nanoparticles were characterized with FTIR, XRD and VSM. Cyclic voltammetry was carried out to verify electrochemical behaviors of the co-immobilized laccase and TEMPO nanoparticles. When the co-immobilized laccase and TEMPO nanoparticles were used to decolorize acid fuchsin, the maximum decolorization rate of 77.41% was obtained with the ratio of TEMPO to laccase being 0.3 mM/g:120 U/g
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