. Tannase enzyme from Aspergillus oryzae was immobilized on various carriers by different methods. The immobilized enzyme on chitosan with a bifunctional agent (glutaraldehyde) had the highest activity. The catalytic properties and stability of the immobilized tannase were compared with the corresponding free enzyme. The bound enzyme retained 20·3% of the original specific activity exhibited by the free enzyme. The optimum pH of the immobilized enzyme was shifted to a more acidic range compared with the free enzyme. The optimum temperature of the reaction was determined to be 40°C for the free enzyme and 55°C for the immobilized form. The stability at low pH, as well as thermal stability, were significantly improved by the immobilization process. The immobilized enzyme exhibited mass transfer limitation as reflected by a higher apparent K m value and a lower energy of activation. The immobilized enzyme retained about 85% of the initial catalytic activity, even after being used 17 times.

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-Aspergillus aculeatus tannase was immobilized on several carriers by entrapment and covalent binding with cross-linking. Tannase immobilized on gelatin with cross-linking agent showed the highest activity and immobilization yield. The optimum pH of the immobilized enzyme was shifted to a more acidic range compared with the free enzyme (from pH 5.5 to pH 5.0). The optimum temperature of the reaction was determined to be 50°C for the free enzyme and 60°C for the immobilized form. The thermal stability, as well as stability over a wide range of pH, was significantly improved by the immobilization process. The calculated K m of the immobilized tannase (11.8 mg ml -1 ) is higher than that of the free tannase (6.5 mg ml -1 ), while V max of the immobilized enzyme (0.32 U (µg protein) -1 ) is lower than that of the free tannase (2.7 U (µg protein) -1 ). The immobilized enzyme was able to retain 84 % of the initial catalytic activity after 5.0 cycles.

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