Stabilization of <Bacillus licheniformis</i> 5A1 urease by covalent attachement to wool

Abstract

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 CaCl<sup>2 (10mM) and immobilization processes protected the enzyme against inhibitors like Cu2+.

Egyptian Journal of Biotechnology Vol. 25 (1) 2007: pp. 70-81</sup>