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首页> 外文期刊>African Journal of Biotechnology >An alkaliphilic cyclodextrin glycosyltransferase from a new Bacillus agaradhaerens WN-I strain isolated from an Egyptian soda lake: Purification and properties
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An alkaliphilic cyclodextrin glycosyltransferase from a new Bacillus agaradhaerens WN-I strain isolated from an Egyptian soda lake: Purification and properties

机译：从埃及苏打湖分离得到的新芽孢杆菌琼脂芽孢杆菌WN-1菌株的一种碱性环糊精糖基转移酶：纯化和性质

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摘要

Alkaliphilic bacteria were isolated from soil and water samples obtained from Egyptian soda lakes in the Wadi Natrun area. Screening for cyclodextrin glycosyltransferase- producing alkaliphilic bacteria resulted in the isolation of 15 positive strains. Strain WN-I was selected as the best producer of CGTase. 16S rDNA sequence analysis and DNA-DNA hybridization identified the isolate asBacillus agaradhaerens. The enzyme was purified to homogeneity up to 21 fold by starch adsorption and anion exchange chromatography with a yield of 26.40%. The pure enzyme was a monomer with an estimated molecular weight of 85 kDa. The enzyme was stable, at 25°C, over a pH range of 5.0 to 11, with a maximum activity at pH 9.0. The enzyme activity exhibited an optimum temperature of 55°C and was stable at 40°C for at least 1 h. Thermal stability was ?improved in the presence of maltodextrin, starch or CaCl2.?The enzyme was slightly stimulated by CaCl2, KC1 and?BaCl2?but was completely inhibited in the presence of FeCl2?and strongly inhibited by ZnCl2?and CoCl2?and to a lower extent by CuCl2, EDTA, 2-mercaptoethanol, and dithiothritol. The enzyme produced mainly β-CD (71.20% of the total cyclodextrin amount). The enzyme had higher cyclyzation activity (1.9 fold higher) toward Paselli starch than soluble starch.
机译：从Wadi Natrun地区的埃及苏打湖中获得的土壤和水样中分离出嗜碱细菌。筛选产生环糊精糖基转移酶的嗜碱细菌导致分离出15株阳性菌株。 WN-1菌株被选为CGTase的最佳生产者。 16S rDNA序列分析和DNA-DNA杂交鉴定了分离株为芽孢杆菌。通过淀粉吸附和阴离子交换层析将酶纯化至最高21倍的同质性，收率为26.40％。纯酶是估计分子量为85 kDa的单体。该酶在25℃，5.0至11的pH范围内稳定，在pH 9.0时具有最大活性。酶活性显示出最适温度为55°C，并在40°C稳定至少1小时。在麦芽糖糊精，淀粉或CaCl2存在下，热稳定性得到了改善。该酶被CaCl2，KCl和BaCl2轻微刺激，但在FeCl2存在下被完全抑制，而ZnCl2和CoCl2则强烈被抑制。 CuCl2，EDTA，2-巯基乙醇和二硫苏糖醇的含量较低。该酶主要产生β-CD（占环糊精总量的71.20％）。该酶对帕塞利淀粉的环化活性比可溶性淀粉高（1.9倍）。

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