Highly thermostable and alkaline α-amylase from a halotolerant-alkaliphilic Bacillus sp. AB68

An alkaliphilic and highly thermostable α-amylase producing Bacillus sp. was isolated from Van soda lake. Enzyme synthesis occurred at temperatures between 25°C and 40°C. Analysis of the enzyme by SDS-PAGE revealed a single band which was estimated to be 66 kDa. The enzyme was active in a broad temperature range, between 20°C and 90°C, with an optimum at 50°C; and maximum activity was at pH 10.5. The enzyme was almost completely stable up to 80°C with a remaining activity over 90% after 30 min pre-incubation. Thermostability was not increased in the presence of Ca(2+). An average of 75% and 60°C of remaining activity was observed when the enzyme was incubated between pH 5 and 9 for 1 h and for 2 h, respectively. The activity of the enzyme was inhibited by SDS and EDTA by 38% and 34%, respectively.