期刊
FEMS MICROBIOLOGY LETTERS
卷 329, 期 2, 页码 204-211出版社
WILEY-BLACKWELL
DOI: 10.1111/j.1574-6968.2012.02522.x
关键词
ss-amylase; organic solvent tolerance; purification; Salimicrobium; serine protease
类别
A halophilic isolate Salimicrobium halophilum strain LY20 producing extracellular amylase and protease was isolated from Yuncheng, China. Production of both enzymes was synchronized with bacterial growth and reached a maximum level during the early-stationary phase. The amylase and protease were purified to homogeneity with molecular weights of 81 and 30 similar to kDa, respectively. Optimal amylase activity was observed at 70 similar to degrees C, pH 10.0% and 10% NaCl. Complete inhibition by EDTA, diethyl pyrocarbonate (DEPC), and phenylarsine oxide (PAO) indicated that the amylase was a metalloenzyme with histidine and cysteine residues essential for its catalysis. Maltose was the main product of starch hydrolysis, indicating an beta-amylase activity. The purified protease from LY20 showed highest activity at 80 similar to degrees C, pH 10.0% and 12.5% NaCl. Complete inhibition was shown by phenylmethylsulfonyl fluoride, DEPC, and PAO, indicating that the enzyme probably belonged to the subclass of the serine proteases with histidine and cysteine residues essential for catalysis. Furthermore, both enzymes were highly stable over broad temperature (3080 similar to degrees C), pH (6.012.0) and NaCl concentration (2.520%) ranges, showing excellent thermostable, alkalistable, and halotolerant nature. The surfactants (SDS, Tween 80, and Triton X-100) did not affect their activities. In addition, both enzymes from LY20 displayed remarkable stability in the presence of water-soluble organic solvents with log Pow similar to=similar to-0.24.
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