Characterization of a-amylase produced by thermophilic bacteria isolated from Iranian hot spring waters
2009
Farahmand, M., Azad University | Mozaffari, N. A., Member of Scientific Board of Faculty of Medicine Sciences of Iran | Mehrabian, S., Member of Scientific Board of Tarbiat Moalem University | Khavarinejad, R., Member of Scientific Board of Azad University
Thermophilic bacteria are valuable sources of thermostable hydrolytic enzymes. Heat-stable enzymes have immense importance in industry and are generally utilized for a variety of commercial Purposes. Among the starch hydrolyzing enzymes, ¥á-amylases have considerable commercial value, especially in sweetener industry. For the production process of sweeteners from starch, the temperature should be 50¨¬c or higher and the pH close to 7 in order to prevent browning effects and reduce viscosity. It thus requires enzymes able to withstand the elevated process temperatures. Bacteria were isolated from two hot spring waters of Kharaghan (in Gazvin province) and Mahallat ( in Arak). Water samples were collected from 50cm below the spring water surface.The water temperatures at the time of sampling at the Kharaghan and Mahallat sites were 56¨¬ c and 48¨¬ c, respectively. Following centrifugation of the water samples, any remaining pellets were cultured in trace element enriched nutrient broth and incubated at proper elevated temperatures. The four recovered bacteria were identified molecularly by PCR and 16S rRNA gene ribotyping. They were identified as Aneurinibacillus aneurinilyticus, Aneurinibacillus thermoaerophilus, Anoxybacillus pushinoensis and Bacillus licheniformis. Amylase production was assayed on starch agar plates by dinitrosalicylic assay. The optimal pH and temperature for enzyme activity were characterized.The maximum activity for the B.licheniformis enzyme was observed at 70¨¬ c and at pH 7.0. The A.aneurinilyticus enzyme maximum activity was at 70¨¬ c and at pH 8.0 ; whereas , these for the A.pushinoensis enzyme was at 80¨¬ c and at pH 8.0 .
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