Abstract:
With the rapid advancement of industrialization and urbanization, high-risk pollutants—including antibiotics, endocrine-disrupting compounds, polycyclic aromatic hydrocarbons, pesticides, and synthetic dyes—are now recognized as persistent contaminants in aquatic environments. These contaminants are characterized by high toxicity, environmental persistence, bioaccumulation potential, and resistance to conventional treatment processes, thereby posing long-term risks to ecological and human health. Traditional physicochemical methods often suffer from high energy consumption, limited selectivity, incomplete mineralization, and the risk of secondary pollution, underscoring the urgent need for efficient and sustainable alternatives. Laccase, a multicopper oxidase that utilizes molecular oxygen as the terminal electron acceptor, has emerged as a promising green biocatalyst due to its broad substrate spectrum, mild operating conditions, and low environmental impact. It can directly oxidize phenolic and aromatic amine compounds and, in the presence of low-molecular-weight mediators, expand its catalytic scope to non-phenolic and high-redox-potential pollutants. However, the practical application of free laccase is hindered by poor operational stability, rapid deactivation, and limited reusability in complex wastewater systems. Immobilization is widely employed to overcome these limitations by anchoring enzymes onto or within solid supports, thereby enhancing structural stability, improving resistance to environmental fluctuations, and enabling enzyme recovery and reuse. In parallel, genetic engineering strategies have been developed to improve enzyme yield, catalytic efficiency, and environmental adaptability. These two approaches are increasingly integrated to construct robust biocatalytic systems. This review systematically summarizes recent advances in immobilized laccase systems for the degradation of high-risk pollutants. Major immobilization strategies, including adsorption, covalent bonding, entrapment, cross-linked enzyme aggregates (CLEAs), and composite immobilization, are comparatively analyzed in terms of their mechanisms, carrier materials, operational performance, and pollutant specificity. Among these, composite immobilization has demonstrated superior performance by coupling adsorption-driven enrichment with catalytic degradation, often achieving removal efficiencies exceeding 90% along with enhanced operational stability. Furthermore, the integration of immobilization with genetically engineered laccase-producing microorganisms is highlighted. Particularly, immobilized whole-cell systems and carrier-attached biofilms enable continuous enzyme expression, prolonged catalytic activity, and improved adaptability to dynamic wastewater environments. In practical applications, immobilized laccase systems exhibit strong tolerance to complex matrices and maintain high degradation efficiencies in mixed-contaminant systems, such as pharmaceutical–dye and phenol–antibiotic wastewaters. Notably, advanced carriers, including magnetic nanomaterials and biochar-based composites, further enhance stability under extreme conditions, such as alkaline pH, high salinity, and temperature fluctuations. Overall, immobilized laccase systems show significant potential for treating dye wastewater, pharmaceutical effluents, municipal secondary effluents, and phenol-containing industrial wastewater. Future research should focus on developing novel biodegradable composite carriers, optimizing immobilization strategies to minimize activity loss, validating these systems at a large scale in real wastewater, and comprehensively evaluating long-term stability and cost-effectiveness. These efforts will facilitate the practical implementation of laccase-based biocatalytic technologies in sustainable environmental remediation.