Original Article Purification and Characterization of a Cold-Adapted a-Amylase Produced by Nocardiopsis sp. 7326 Isolated from Prydz Bay, Antarctic

An actinomycete strain 7326 producing cold-adapted a-amylase was isolated from the deep sea sediment of Prydz Bay, Antarctic. It was identified as Nocardiopsis based on morphology, 16S rRNA gene sequence analysis, and physiological and biochemical charac-teristics. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and zymogram activity staining of purified amylase showed a single band equal to a molecular mass of about 55 kDa. The optimal activ-ity temperature of Nocardiopsis sp. 7326 amylase was 35-C, and the activity decreased dramatically at temperatures above 45-C. The enzyme was stable between pH 5 and 10, and exhibited a maximal activity at pH 8.0. Ca2+, Mn2+, Mg2+, Cu2+, and Co2+ stimulated the activity of the enzyme significantly, and Rb2+, Hg2+, and EDTA inhibited the activity. The hydrolysates of soluble starch by the enzyme were mainly glucose, maltose, and maltotriose. This is the first report on the isolation and characterization of cold-adapted amylase from Nocardiopsis sp