Enzymes are widely recognized as environmentally friendly catalysts for pollutant degradation due to their high catalytic efficiency, substrate specificity, and eco-compatibility. However, the practical application of free enzymes in environmental remediation is constrained by their sensitivity to external factors such as pH, temperature, and ionic strength. In this study, Trametes versicolor laccase was immobilized and cross-linked onto biochar to improve its stability, reusability, and catalytic performance in the degradation of polycyclic aromatic hydrocarbons (PAHs). The immobilized laccase, particularly the wheat-derived W700-LC composite, exhibited markedly enhanced stability across a broad range of pH (4–5), salinity (0.1–0.3%), and temperature (25–35℃) compared with its free counterpart. Under optimal conditions (1 mM ABTS or HBT as mediator, pH 5.0, 30 ℃, 12 h), W700-LC achieved removal efficiencies of 75.64% (PYR) and 84.39% (BAP) in the ABTS system, and 78.83% (PYR) and 71.09% (BAP) in the HBT system. Moreover, it retained approximately 80% of its activity after five consecutive reuse cycles. The optimal degradation performance was obtained under pH 5–6, salinity 0.1–0.3%, PAHs concentrations of 1–10 mg/L, and enzyme loading of 20–25 g/L. GC–TQMS analysis combined with molecular docking revealed that laccase-mediated radical chain reactions—including ring-opening, molecular rearrangement, and radical coupling—dominated the degradation pathways, with hydrophobic interactions playing a pivotal role in stabilizing laccase–PAHs complexes. These findings demonstrate that biochar-based enzyme immobilization significantly enhances environmental adaptability and recyclability, offering a cost-effective and robust strategy for enzyme-assisted bioremediation. This work provides valuable insights into advancing the practical application of laccase in soil and water remediation of PAHs contamination.
 

Laccase immobilization; Biochar carrier; Polycyclic aromatic hydrocarbons; Bioremediation; Radical degradation mechanism