Kinetic study of tyrosinase immobilized on polymeric membrane

Kinetic properties of tyrosinase immobilized on a polymeric membrane for the production of l-3,4-dihydroxyphenylalanine (l-DOPA) were investigated. A comparison with the properties shown by the free enzyme used in a stirred tank reactor was also carried out. The values of the Michaelis–Menten constant indicated that the immobilized tyrosinase exhibited better affinity for the substrate (Km=1.56 mM and 2.10 mM for the immobilized and free enzyme, respectively). The stability (pH, thermal, storage and operational) of both free and immobilized tyrosinase was also evaluated. Results showed that the immobilization enhanced the enzyme stability. The optimum pH and temperature for the activity of both free and immobilized enzyme were found at pH 7.0 and 35 °C, respectively. However, the immobilized tyrosinase was more stable in the whole range of pH and temperature. These advantages of the immobilized enzyme make it a good candidate for its use in different industrial processes.