Purification and biochemical characterization of a novel SDS and surfactant stable, raw starch digesting, and halophilic α-amylase from a moderately halophilic bacterium, Nesterenkonia sp strain F

An extracellular halophilic alpha-amylase from Nesterenkonia sp. strain F was purified to homogeneity by 80% ethanol precipitation, Q-Sepharose anion exchange and Sephacryl S-200 gel filtration chromatography, with a 10.8-fold increase in specific activity. The molecular mass of the amylase was estimated to be 100 kDa and 106 kDa by SDS-PAGE and gel filtration chromatography, respectively. The enzyme showed maximal activity at pH 7.5 and 45 C. The amylase was active in a wide range of salt concentrations (0-4 M) with its maximum activity at 0.5 M NaCl or 1 M KCl and was stable at the salts concentrations between 1 M and 4 M. Fe(3+), Cu(2+), Zn(2+) and Al(3+) strongly inhibited the enzyme, whereas Ca(2+) stimulated the amylase activity. The a-amylase was inhibited by EDTA, but was not inhibited by PMSF and beta-mercaptoethanol. The enzyme showed remarkable stability towards 0.5% SDS and sarcosyl, and 2% each of Triton X-100, Tween 80 and Tween 20. K(m) value of the amylase for soluble starch was 4.5 mg/ml. The amylase hydrolyzed 38% of raw wheat starch and 20% of corn starch in a period of 48 h. The major products of soluble starch hydrolysis were maltose, maltotriose and maltotetraose, indicating an a-amylase activity. (C) 2010 Elsevier Ltd. All rights reserved.