There are two commercially-used forms of this starch-hydrolyzing enzyme:
Alpha amylase breaks the alpha-1,4-glucosidic bonds of starch to yield oligosaccharides. Slightly different versions of this enzyme are produced by the bacteria Bacillus amyloliquefaciens, B. licheniformis, B. subtilis and the fungus Aspergillus oryzae. Alpha amylase is used to make corn syrup, beer, wallpaper removers, cold-soluble laundry starch, and digestive aids.
Beta amylase has exo-alpha-1,4-glucanase activity and acts on linear alpha-1,4-linked glucans, breaking alternate bonds to form maltose. This enzyme is found in most plants but is rare in fungi and bacteria; it is the amylase produced by germinating barley, which is used in beer production.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.