A halophilic isolate Thalassobacillus sp. LY18 producing extracellular amylase was isolated from the saline soil of Yuncheng Salt Lake, China. Production of the enzyme was synchronized with bacterial growth and reached a maximum level during the early stationary phase. The amylase was purified to homogeneity with a molecular mass of 31 kDa. Major products of soluble starch hydrolysis were maltose and maltotriose, indicating an α-amylase activity. Optimal enzyme activity was found to be at 70°C, pH 9.0, and 10 % NaCl. The α-amylase was highly stable over broad temperature (30-90°C), pH (6.0-12.0), and NaCl concentration (0-20 %) ranges, showing excellent thermostable, alkalistable, and halotolerant nature. The enzyme was stimulated by Ca(2+), but greatly inhibited by EDTA, indicating it was a metalloenzyme. Complete inhibition by diethyl pyrocarbonate and β-mercaptoethanol revealed that histidine residue and disulfide bond were essential for enzyme catalysis. The surfactants tested had no significant effects on the amylase activity. Furthermore, it showed high activity and stability in the presence of water-insoluble organic solvents with log P (ow) ≥ 2.13.

• MeSH
• alpha-Amylases chemistry   genetics   metabolism   MeSH
• Bacillaceae chemistry   enzymology   genetics   isolation & purification   MeSH
• Bacterial Proteins chemistry   genetics   metabolism   MeSH
• Lakes microbiology   MeSH
• Starch metabolism   MeSH
• Enzyme Stability MeSH
• Hot Temperature MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• China MeSH
• Names of Substances
• alpha-Amylases MeSH
• Bacterial Proteins MeSH
• Starch MeSH