Simultaneous purification and immobilization of laccase on magnetic zeolitic imidazolate frameworks: Recyclable biocatalysts with enhanced stability for dye decolorization

摘要

Laccases are versatile oxidases showing strong ability to eliminate hazardous pollutants from wastewater. Magnetic zeolitic imidazolate framework-8 (Fe304@ZIF-8) nanoparticles were synthesized by a facile method and used for single-step purification and immobilization of recombinant laccase from Escherichia coli culture supernatant. An activity recovery of 75.7% was achieved for the immobilized biocatalyst. The storage and thermal stability of laccase was remarkably enhanced after immobilization. The immobilized laccase exhibited optimum temperature at 80°C. It retained about 46.0% of initial activity after 6 h incubation at 80°C, while the free laccase was totally inactivated by this treatment. In addition, the immobilized enzyme maintained 87.1% activity after 10 days of storage at 30°C. Finally, excellent reusability was also observed for the immobilized laccase, which was able to completely decolorize indigo carmine after 5 consecutive cycles. Therefore, the immobilization of laccase on Fe304@ZIF-8 nanoparticles offers a facile and cost-effective way for environmental application of bacterial laccase.