Industrial Production of Cyclodextrins

We isolated three alkalophilic bacteria producing large amount of cyclodextrin glycosyltransferases (CGTases). Two of the enzymes, CGTases of Bacillus No. 38–2 and Bacillus No. 17–1 were purified by starch adsorption and DEAE-cellulose chromatography followed by gel filtration. The enzymes were very thermostable, especially Bacillus No. 38–2 enzyme was not inactivated up to 70 C. The enzymes isolated converted about 65–80% of potato starch to cyclodextrins at 1% (w/v) substrate concentration. Through the CGTase of Bacillus No. 38–2, crystalline β-cyclodextrin, γ-cyclodextrin and a mixture of cyclic and acyclic dextrins were produced on an industrial scale plant without using any organic solvent. One ton of potato starch suspension (15% w/v) containing 10 mM CaCl2 was liquefied by the CGTase at 90 С (pH 8.5) and then cooled to 60 C. The liquefite was readjusted to pH 8.5 with CaCO3 and CGTase was added again. The cyclodextrin formation was maintained at 60 С for 45 h. After the reaction, the enzyme was inactivated at 80 C. The appreciable amount of bacterial α-amylase was added (pH 6.0) to hydrolyse saccharide which were not converted to cyclodextrin. The digest was decolorised and passed through ion exchangers. The refined digest was concentrated to 45% (w/v) and transfered to a crystallizer. The crystalline β-cyclodextrin was collected by centrifugation. The filtrate containing cyclodextrins is available as CH for food additives. From this CH, γ-cyclodextrin was produced. The CH was treated with gluco-anylase and passed through a Toyo Pearl HW-40 column to separate γ-cyclodextrin from other saccharides. The γ-cyclodextrin thus prepared was crystallised directly from water.