BACKGROUND: Immobilized enzymes provide many advantages over free enzymes including repeated or continuous reuse, easy separation of the product from reaction media, easy recovery of the enzyme, and improvement in enzyme stability. In order to improve catalytic activity of laccase and increase its industrial application, there is great interest in developing novel technologies on laccase immobilization. RESULTS: Magnetic Cu2+-chelated particles, prepared by cerium-initiated graft polymerization of tentacle-type polymer chains with iminodiacetic acid (IDA) as chelating ligand, were employed for Pycnoporus sanguineus laccase immobilization. The particles showed an obvious high adsorption capacity of laccase (94.1 mg g(-1) support) with an activity recovery of 68.0% after immobilization. The laccase exhibited improved stability in reaction conditions over a broad temperature range between 45 degrees C and 70 degrees C and an optimal pH value of 3.0 after being adsorbed on the magnetic metal-chelated particles. The value of the Michaelis constant (K-m) of the immobilized laccase (1.597 mmol L-1) was higher than that of the free one (0.761 mmol L-1), whereas the maximum velocity (V-max) was lower for the adsorbed laccase. Storage stability and temperature endurance of the immobilized laccase were found to increase greatly, and the immobilized laccase retained 87.8% of its initial activity after 10 successive batch reactions. CONCLUSION: The immobilized laccase not only can be operated magnetically, but also exhibits remarkably improved catalytic capacity and stability properties for various parameters, such as pH, temperature, reuse, and storage time, which can provide economic advantages for large-scale biotechnological applications of laccase. (c) 2007 Society of Chemical Industry.