5A1 urease by covalent attachement to wool
The investigation of five bacterial strains for urease production referred that Bacillus licheniformis 5A1 had the highest urease activity (10.3U/ml/min) after 24h. The enzyme was covalently coupled to different carriers via glutaraldehyde, and wool gave the highest immobilization yield (76.4%) and retained 85% of the original specific activity. The immobilized urease retained 62% of its activity when incubated at 50°C for 45min and was quietly stable at higher temperature. The optimum reaction temperatures of the free and the immobilized urease were 40 and 45°C respectively. The optimum pH of free urease (7.0) apparently was shifted 1.0 unit acidic region upon immobilization. . Activation energy ( EA ) of free and immobilized urease were 7.91 and 3.64 Kcal/mol respectively . Deactivation rate constant at 60°C of both free and immobilized urease were 3.2x10-2 and 0.7x10-2/min, respectively. Half-life time ( t1/2 ) at 50°C of immobilized urease was higher than free urease ( 58.5 and 12.3 min, respectively). The immobilized enzyme was repeated 13 times with 70% residual activity and would have promise in clinical and industrial uses. The activity of both free and immobilized urease were significantly improved by addition of CaCl2 (10mM) and immobilization processes protected the enzyme against inhibitors like Cu2+.
Egyptian Journal of Biotechnology Vol. 25 (1) 2007: pp. 70-81