Abstract

A β-cyclodextrin glycosyltransferase (β-CGTase) from a new alkalitolerant Bacillus sp. SK 13.002 strain which can significantly hydrolyze starch into short linear saccharides, in addition to production of cyclodextrins (CDs) was produced. The hydrolytic activity of this CGTase as a side reaction is thought to be due to partial retention of ancestral enzyme function from evolution over time. This CGTase is therefore another example of an enzyme at an intermediary stage in between ‘‘true’’ α-amylases and ‘‘true’’ CGTases. The strain also produced two CGTase isozymes which were purified to homogeneity using DEAE-Sepharose anion exchange chromatography and Superdex 75 gel filtration chromatography to show Molecular masses of 67.5 and 46.8 kDa on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) respectively, which were confirmed by liquid chromatography/mass spectrometry (LC/MS) analysis to be 67.6 and 47.3 kDa, respectively. Both CGTase isozymes formed CDs from soluble starch. Most of the reported CGTases were composed of one single enzyme with only a few strains having CGTase isozymes showing different isoelectric points. Therefore, Bacillus sp. SK 13.002 strain is another Bacillus capable of producing CGTase isozymes which were individually purified to homogeneity.

Key words: Cyclodextrin glycosyltransferase, production, Bacillus, isozyme, cyclodextrin,purification.