UREASE IMMOBILIZED ON MODIFIED POLYSULFONE MEMBRANE - PREPARATION ANDPROPERTIES

Porous asymmetric membranes were formed by the phase inversion method from one-to-one blends of polysulphone and its aminated derivative. Am ino groups were introduced into polysulphone UDEL P 1700 by chlorosulp honation followed by amination. Urease was immobilized on the modified polysulphone membranes. The properties of the immobilized urease were investigated and related to the free enzyme. The Michaelis constant w as 4.4 times higher for the immobilized than for the free urease. Immo bilization improved the pH stability of the enzyme at pH < 6.5 as well as its temperature stability. However, the immobilization did not pro tect the enzyme against heat inactivation at 70 degrees C; the half-ti mes for the activity decay were equal to 120 and 50 min for the free a nd immobilized enzymes, respectively. The immobilized urease exhibited good storage and operational stability, and good reusability, propert ies that prove the applicability of the obtained system in enzymatic-m embrane reactors.