Turkish Journal of Biology




The moderately halophilic Halomonas sp. strain AAD21, which produces extracellular thermostable \alpha-amylase, was isolated from the Çamaltı Saltern area located in İzmir, Turkey. NaCl, carbon, and nitrogen sources in the growth medium were optimized to enhance \alpha-amylase yield. The highest enzyme yield was measured in the presence of 20% NaCl with peptone as the nitrogen and starch as the carbon sources in the fermentation broth. This microorganism was also found to utilize waste potato peel as a carbon source for \alpha-amylase production. Concentrations of carbon and nitrogen sources were optimized using a statistical approach, and \alpha-amylase activity increased from 4.07 U mL^-^1 min^-^1 to 26.25 U mL^-^1 min^-^1. Maximum \alpha-amylase production was achieved at the end of 48 h of growth in the presence of 20% NaCl, 4.12% starch, 1.0% peptone, 0.2% KCl, 2% MgSO_{4}.7H_{2}O, and 0.03% trisodium citrate pentahydrate. The optimum pH and temperature of the \alpha-amylase were found to be 7.0 and 50 °C, respectively. The \alpha-amylase synthesized by Halomonas sp. AAD21 was also thermostable. Crude \alpha-amylase did not lose its original activity after 2 h of incubation at 50 °C and 60 °C, and it retained 70% of its original activity after 120 min of incubation at 90 °C.

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