Abstract: A thermophilic strain CW₂, which can produce a type of starchdegrading enzyme, was isolated from the soil around a hot spring in the Changbai Mountains. The products from starch by the enzyme were determined by thin layer chromatography (TLC) and the results show that the enzyme is a kind of ectoenzyme that could catalyze the degradation of starch to produce isomaltooligosaccharide including isomaltose, isomaltotriose, and panose as dominant products. The 16S rDNA of the strain was amp lified by PCR and was sequenced (873bp), and then was compared with those available in the GenBank databases. The result shows that CW₂ 16S rDNA sequence is most similar to that of Bacillus licheniformis ATCC 14580,Bacillus licheniformis DSM 13 and Bacillus subtilis strain JM4, there are only 9,9,13 different bases between every pair of sequences, the sequence similarities are 98.97％,98.97％,98.51％, respectively. The phylogenetic trees including CW₂ were derived with neighbor joining and analyzed with Bootstraping. The results demonstrate that CW₂ strain is close consanguinity to Bacillus licheniformis and Bacillus sonorensiss, they belong to the same sister cluster in Bacillus group. 

Key words: hot spring in the Changbai Mountains, thermophile, isomaltooligosaccharide, starch