The Bacillus thuringiensis strain ZA96 was isolated from petroleum-contaminated soils. The capability of the bacterium to remove acrylonitrile was confirmed by the phenol red test. A 25-kDa nitrile hydratase was purified by Q-sepharose chromatography. The purified enzyme was encapsulated using 2% sodium alginate. The diameter of microcapsules was 2 mm and enzyme loading and immobilization percent were 66.67% and 94.5%, respectively. The optimal pH for the free enzyme and its immobilized form were 7 and 8.5, respectively. The optimum temperatures were 25 and 35 °C, for the free and immobilized enzymes, respectively. Results showed that the immobilized enzyme had more stability than the free enzyme against temperature, pH, inhibitors, and applied detergents. In comparison with the free enzyme, the stability of the immobilized enzyme was doubled during storage at 4 °C. Microcapsules containing the enzymes, especially in freeze-dried form, could be used to create biosensors to detect nitrile compounds in soil and water environments.

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