الخلاصة

The objective of the present work is to prepare an immobilized urease on Dowex® ion exchange resin and study of its activity in comparing with free mobilized enzyme. The second aim is to use the enzyme-resin complex as a reactor to produce ammonia and carbon dioxide from urea substrate. The immobilization occurred via ion exchange phenomena. This fact confirmed through the release of hydroxide ions in the collected fraction after adding the urease enzyme. Appearance of purple color after adding a drop of phenolphthaline indicator to the fractions indicating the presence of hydroxide ions in the collected fractions. The other confirmation occurred by estimating the protein (urease enzyme) in the fractions. Protein assayed by the Bradford assay. Immobilized urease activity was estimated by salicylate-hypochlorite method. The results of the immobilization process indicating full immobilization of urease enzyme on the resin surface and the immobilized urease that have the ability to hydrolyze urea in about 87% of the free enzyme. The immobilized urease showed good stability and no significant change noticed in its activity after 15 days of storage at room temperature while it covered with a layer of distilled water. It is concluded that a new immobilized urease enzyme on Dowex® resin is prepared with good enzyme activity and stability. A complete kinetic study is the project of a new research. Key words: Dowex, urease