A triple-modified co-immobilized laccase system with dual mediators on MnMOF: Enhanced dye degradation and wastewater detoxification for safe rice seedling cultivation.

Abstract

Laccase provides a green and eco-friendly solution for the degradation of widely used anthraquinone and triphenylmethane dyes. However, its practical application remains constrained by several obstacles, including poor stability, low redox potential, and mediator leakage, which affect both dye degradation efficiency and environmental safety. To address these challenges, this study developed a novel co-immobilized laccase-mediator system (LMS), termed MnMOF@LCC5@M@PEG, through a sequential triple-modification strategy involving the in-situ immobilization of laccase (LCC5) within a manganese-based metal-organic framework (MnMOF), co-immobilization of two redox mediators (ABTS and p-coumaric acid (pCA)), and final surface crosslinking with polyethylene glycol (PEG). Compared with the free enzyme, the MnMOF@LCC5@M@PEG composite exhibited a relative activity of 292.03%, improved thermal stability, enhanced tolerance to organic solvents and metal ions, and excellent reusability. Moreover, the composite not only achieved efficient degradation of 100 mg/L Alizarin Red within 15 min and 68.22% degradation of 10 mg/L Crystal Violet within 50 h, but also maintained high degradation efficiency in various real water matrices and retained over 70% of its initial activity after five consecutive reuse cycles. Furthermore, a specific dual-sieve filtration device containing MnMOF@LCC5@M@PEG was constructed, which could not only effectively and stably treat the dye wastewater, but also produce effluent that supported normal rice seedling growth. Therefore, we developed a robust and recyclable biocatalytic platform by constructing a triple-modified immobilized LMS and dual-sieve filtration device, which detoxified dye wastewater to levels safe for rice seedling cultivation, thereby offering a high-performance and sustainable solution for enzyme immobilization and the treatment of dye-contaminated wastewater.