Ionic liquid functionalized magnetic polydopamine enhancing enzyme stability and catalytic efficiency for water pollutant treatment

Laccase has received widespread attention in pollutant degradation, but the current challenges in its poor stability, easy inactivation, and difficult recovery have seriously affected the application. The enzyme immobilization technology is a crucial approach to enhance the stability, recoverability, and other valuable properties to improve the effectiveness of biocatalysts. In this study, a polydopamine coating Fe₃O₄ nanoparticle was modified with an ionic liquid, which can be used for laccase immobilization. The incorporation of polydopamine provided a biocompatible and reactive coating for nanoparticles, while the presence of ionic liquids ensured that enzyme molecules were positioned away from the carrier surface, which facilitated the stabilization of the spatial structure of the enzyme and the retention of its activity. The immobilized laccase exhibited a broad pH and temperature and satisfactory stability. The activity of immobilized laccase remained at approximately 80 % of its activity even after incubation at 50 ℃, and over 65 % activity at storage for 30 days, which is 1.6 times and 2.9 times higher than the free laccase, respectively. The biocatalytic demonstrated excellent removal of phenolic contaminants, achieving removal efficiencies of approximately 97 % for 2,4-dichlorophenol. The remarkable magnetic response greatly facilitates the collection and subsequent reuse of the biocatalyst up to six times while still maintaining a relative removal efficiency of over 70 % for 2,4-dichlorophenol. Furthermore, the biocatalytic also exhibited excellent removal efficiency for Bisphenol A and phenol, which were 1.5 and 1.4 times more effective than the free laccase. The immobilization method provided in this work offers new ideas for the development and efficient biological enzyme preparation for industrial wastewater treatment.