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A bacterial strain No. KY-126, which produced extracellular cyclodextrin glycosyltransferase(CGTase), was isolated from soil and identified as Bacillus stearothermophilus KY-126. The enzyme was purified by the treatments of ammonium sulfate precipitation, DEAF-Sephadex, Sephadex G-100 column chromatography. The optimal pH and temperature for the enzyme activity were pH 5.5 and 65℃, respectively. And the enzyme was stable at pH values from 6.0 to 11.0 at 55℃ for 30 min and stable up to 60℃ for 30 min.. The enzyme was inhibited by HgClz. The molecular weight of the enzyme was estimated to be 67,000 by using SDS-PAGE. The maximum conversion from starch to cyclodextrin (CD) by CGTase was 43%r and obtained at 6 hr reaction and the ratio of α-, α-, γ-, CD prodyction at this time was 2.9 : 2.1 : 1.0.
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