Abstract: It is the key to prepare a perfect carrier for enzyme immobilization for increasing enzyme loading,efficient use and reducing the cost of enzyme application. Magnetical polyaniline nanocomposite was synthesized via mixing aniline solution and Fe₃O₄ nanoparticles and used as laccase immobilization carrier. The successful synthesis was confirmed by the results of TEM and FT-IR. Different proportions of Fe₃O₄ and aniline had no significant effect on the structure of the carrier,but the enzyme loading was affected. The maximum loading of the synthetic carrier was 210 mg/g,and the conductive properties of carrier were changed after the laccase was immobilized on it. The optimum reaction pH and temperature for the immobilized laccase were 3.5 and 60℃,respectively. A slight shift of optimal pH was observed. Immobilized laccase kept 50% its activity after incubation at 50℃ for 240 min,and 60% of its activity after incubation at 4℃ for 30 d. Over a period of repeated operation,immobilized laccase still remained about 70% after 8 cycles. With the increase of the proportion of Fe₃O₄,the loading of the carrier reduced,and there was a certain electron exchange between laccase and the carrier. The immobilized laccase can be simply recovered from the reaction solution by a magnet. Immobilized laccase onto Fe₃O₄/polyaniline nanofiber shows high stabilities,easy recovery,and reuse capabilities,which demonstrated that Fe₃O₄/ polyaniline nanofiber is a kind of perfect carrier for enzyme immobilization.

Key words: magnetic nanoparticle, polyaniline, laccase, immobilization