Improved performance of immobilized laccase on Fe₃O₄@C-Cu²⁺ nanoparticles and its application for biodegradation of...

An effective strategy for enhancement of catalytic activity and stability of immobilized laccase via metal affinity adsorption on Fe₃O₄@C-Cu²⁺ nanoparticles was developed, which involved the fabrication of hydroxyl and carboxyl functionalized Fe₃O₄@C nanoparticles via a simple hydrothermal process and the subsequent chelation with Cu²⁺ for the immobilization of laccase under a mild condition. Our results revealed that the Fe₃O₄@C-Cu²⁺ nanoparticles possess a high loading amount of bovine serum albumin (BSA, 436 mg/g support) and laccase activity recovery of 82.3 % after immobilization. Laccase activity assays indicated that thermal and pH stabilities, and resistances to organic solvents and metal ions of the immobilized laccase were relatively higher than those of the free enzyme. The immobilized laccase maintained more than 61 % of its original activity after 10 consecutive reuses. Most importantly, the immobilized laccase possessed excellent degradation of diverse synthetic dyes. The degradation rates of malachite green (MG), brilliant green (BG), crystal violet (CV), azophloxine, Procion red MX-5B, and reactive blue 19 (RB19) was approximately 99, 93, 79, 88, 75 and 81 (%) in the first cycle. Even after 10 consecutive reuses, the removal efficiencies of the six dyes were found to be 94, 80, 71, 78, 60, and 65 (%), respectively.