一株新型产淀粉酶中度嗜热菌的分离鉴定及酶学性质研究

Isolation of a new type moderately thermophilic amylase-producing strain and its enzymatic properties

用稀释分离法从广西象州温泉筛选分离到一株可水解淀粉的中度嗜热细菌GXS1,该菌株革兰氏染色为阳性,端生芽孢,细胞呈杆状,最适生长温度为60℃～65℃,最适生长pH为6.0～7.0。结合生理生化特征和16S rDNA序列分析,初步鉴定该菌株为Geobacillus sp.GXS1。对该菌所产高温淀粉酶的性质研究表明:酶的最适反应温度为80℃,在40℃～60℃范围内稳定,70℃保温30 min仍保留77%残余酶活,最适pH为7.0,稳定pH范围为4.0～10.0。产物经HPLC分析证明,该酶能水解淀粉产生麦芽三糖、麦芽糖和葡萄糖的混合物,对α-环糊精、β-环糊精不起作用。

Using dilution method, a moderately thermophilic amylase-generated bacterium GXS1 was isolated from the Xiangzhou hot spring of Guangxi in China. The cells of the strain GXS1 were gram-positive, sporulation and rod-shaped. Its optimum temperature for growth was between 60℃ and 65E, and its optimum pH for growth was between 6.0 and 7.0. The morphological, physiological characterization and 16S rDNA sequences analysis indicated that the strain GXS1 was relatively close to Geobacillus. Thus the strain GXS1 was preliminarily indentified as Geobacillus sp. GXS1. The characteristics of the thermostable amylase were also discussed. The optimum temperature and pH for the enzyme were determined at 80℃ and7. 0 respectively. The stable temperature and pH range were 40 ℃--60 ℃ and4.0- 10.0 respectively. The amylase exhibited well thermal-stability, retaining 77 % activities after 30 min at 70 ℃. The results of HPLC of products from starch by the amylase demonstrated that the enzyme could be used to produce maltotriose, maltose and glucose from starch, but it could not catalyze α-cyclodextrin and β-cyclodextrin.