Abstract: Twelve amylaseproducing mesophilic strains, newly isolated from Chinese soil were screened according to their ability of starch digestion by clear zone method. Among them, strain ZW2531-1 showed high amylaseproducing ability, and its amylase could catalyze the degradation of starch to produce several oligosccharides including maltose, maltotriose and a large amount of isomaltotriose and isomaltotetraose, without glucose. Strain ZW2531-1 was bacilliform, a spore forming bacterium under an electron microscope. To explorethe phylogenetic position of strain ZW2531-1, its 16S rRNA gene was amplified, sequenced, and then was compared with those of standard bacteria available in Genebank databases. Further, the phylogenetic tree including strain ZW2531-1 was built. All the results regarding strain ZW25311 support that bacterium ZW2531-1 belongs to genus Bacillus, therefore, it could be proposed as Bacillus sp. ZW2531-1.

Key words: amylase, mesophilic bacteria, phylogenetic tree, isomaltooligosaccharide