Reversible immobilization of urease onto Procion Brown MX-5BR-Ni(II) attached polyamide hollow-fibre membranes

Urease was immobilized onto Procion Brown MX-5BR attached and Ni(II) incorporated microporous polyarnide hollow-fibre membrane via adsorption. Urease immobilization onto the polyamide hollow-fibre membrane from aqueous solutions containing different amounts of urease at different pH was investigated in a batch system. The maximum urease immobilization capacity of the polyamide hollow-fibre membrane was 78 mg g(-1) fibre. The retained adsorbed enzyme activity was found to be 37%. However, the urease adsorption onto the polyamide fibre resulted in a threefold increase in enzyme stability with time at 50 degreesC. The Km values were 18 and 22 mM for the free and the immobilized enzymes, respectively. The V-max values were 59.7 U mg(-1) for the free and 25.9 U mg(-1) for the immobilized enzyme. The optimum pH (7.0) apparently was shifted 1.0 unit acidic region upon immobilization via adsorption. The optimum reaction temperature for the free and the immobilized enzymes were determined to be 45 and 55 degreesC, respectively. The dye-Ni(II) attached polyamide hollow-fibre membranes could be repeatedly used for the adsorption/desorption of enzyme without any significant loss in adsorption capacity. (C) 2002 Elsevier Science Ltd. All rights reserved.