Abstract
A covalent immobilization of urease was conducted on carboxylic cation-exchange membranes (CEM) prepared by radiation-initiated graft copolymerization of acrylic acid (AA) on polyethene (PE) thin films. Six types of CEM with different grafting degree (from 26.5 to 95.2%) were used as carry. The carboxyl groups were activated by the carbodiimide method in order to carry out a covalently immobilization. The amount of bound protein and the enzyme activity were determined in each immobilized system. It was established that the urease, immobilized on CEM with 64.2% grafting degree, featured the highest relative activity – 80.32%. The amount of bound protein on this membrane type was 6.01 mg/cm2. The basic characteristics of the immobilized and the free enzymes were determined (pHopt, Topt and pHstab). It was found out that the immobilized urease had greater thermal and storage stability in comparison with the free enzyme. It was proven that CEM with a grafting degree of 64.2% would be a suitable carrier for urease immobilization.
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