The hydrolysis of starch to low molecular weight products, catalyzed by the enzyme, a-amylase is one of the most important and successful commercial enzyme-catalyzed reactions used in the processing industry. From an industrial point of view, mostly bacterial and fungal sources have been used for the production of alpha-amylase. alpha-amylase can be obtained from plants, animals and microorganisms. The properties of each alpha-amylases such as thermostability, pH optimum and their other physicochemical properties are important in the development of most suitable fermentation processes. alpha-amylases can be produced by fungi in large amount but they are usually not heat stable beyond 40 degrees C. On the other hand, bacterial species such as Bacillus subtilis, B. megaterium, B. amyloliquefaciens and B. licheniformis produce more heat stable enzymes. Bacterial species, which produce alpha-amylase enzymes that can withstand a temperature of 70 degrees C have been reported previously. There is often a need to isolate species of microorganisms that can grow at high temperatures and whose enzymes can function at temperature up to 95-100 degrees C. The purpose of this manuscript was to review the literature on the microorganism associated by the production of alpha-amylase on using different substrate, thermostability profile and its industrial application. (C) 2013 Friends Science Publishers