A thermostable alkaline a-amylase producing Bacillus sp. ANT-6 was isolated from soil samples. Enzyme synthesis occurred at temperatures between 25 and 45 degreesC with an optimum of 37 degreesC. There was a slight variation in amylase synthesis within the pH range 7 and 11 with an optimum pH of 9. The optimum temperatures for amylase production and growth were the same. Analyses of the enzyme by sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed a single band, which show amylolytic activity, detected in starch gel. The relative molecular mass of the partial purified enzyme was estimated to be 94 500 Da. The enzyme showed optimum activity at pH 10.5 and 80 degreesC. The partial purified enzyme was highly active in the alkaline range of pH (9.5-13), and it was completely active up to 100 degreesC retaining 85.5% initial activity at pH 10.5. Enzyme activity was enhanced in the presence of 5 mM CaCl2 (110%) and 3 mM PMSF (103%), and inhibition with 5 mM by Zn, Na, Na-sulphide, EDTA (10 mM), Urea (8 M) and SDS (0.1%) was obtained 36.9, 21.5, 22.2, 4.90, 86% and 10.27, respectively. The enzyme was stable (55%) at high alkaline pH for 24 h. So our result showed that the enzyme was both alkaline, thermostable, thermopile and chelator resistant. The ANT-6 amylase enzyme may be suitable in liquefaction of starch, in detergent and textile industries and in other industrial applications. (C) 2003 Elsevier Science Ltd. All rights reserved.