Kalpana Balu Jancy, Pandian Shunmugiah Karutha
Department of Biotechnology, Alagappa University, Karaikudi 630 003, Tamil Nadu, India.
J Basic Microbiol. 2014 Aug;54(8):802-11. doi: 10.1002/jobm.201200732. Epub 2013 May 26.
A halotolerant α-amylase having the ability of digesting the insoluble raw starches was characterized from Bacillus subtilis S8-18, a marine sediment isolate from Palk Bay region. The electrophoresis techniques unveiled that the α-amylase was indeed a monomer with a molecular weight of 57 kDa. The optimum temperature and pH for the enzyme activity were 60 °C and 6.0 respectively. The enzyme was highly stable for 24 h over a wide range of pH from 4.0 to 12.0 by showing 84-94% activity. Interestingly, by retaining 72% activity even after 24 h, the enzyme also showed tolerance towards 28% NaCl. The α-amylase retained a minimum of 93% residual activity in 1 mM concentration for the selected divalent metal ions. The enzyme was found to be chelator resistant as it remained unaffected by 1 mM of EDTA and exhibited 96% activity even at 5 mM concentration. Furthermore, though 1% SDS caused remarkable reduction (68%) in amylase activity, the enzyme showed tolerance towards other detergents (1% of Triton-X and Tween 80) with 85% activity. Additionally, the α-amylase enzyme is capable of hydrolyzing the insoluble raw starch substrates which was evident from the scanning electron microscopic (SEM) and spectrophotometric analyses.
从来自帕尔卡湾地区的海洋沉积物分离株枯草芽孢杆菌S8-18中鉴定出一种具有消化不溶性生淀粉能力的耐盐α-淀粉酶。电泳技术表明，该α-淀粉酶确实是一种分子量为57 kDa的单体。该酶活性的最适温度和pH分别为60°C和6.0。在pH值为4.0至12.0的宽范围内，该酶在24小时内高度稳定，活性为84%-94%。有趣的是，即使在24小时后仍保留72%的活性，该酶对28%的NaCl也表现出耐受性。对于所选的二价金属离子，该α-淀粉酶在1 mM浓度下至少保留93%的残余活性。该酶被发现具有抗螯合剂的特性，因为它不受1 mM EDTA的影响，即使在5 mM浓度下仍表现出96%的活性。此外，虽然1%的SDS导致淀粉酶活性显著降低（68%），但该酶对其他洗涤剂（1%的Triton-X和吐温80）表现出耐受性，活性为85%。此外，扫描电子显微镜（SEM）和分光光度分析表明，α-淀粉酶能够水解不溶性生淀粉底物。
