Thirty Bacteroides strains from the human colon were tested for ability to degrade cyclodextrins (CD). Twenty four strains were able to degrade CD. Cyclodextrinase in two of these strains B. ovatus 3524 and B. distasonis Cl8-7 has been studied.

Organisms were grown on a minimal medium containing CD (0.5%), and cyclodextrinase activity was assayed by measuring the increase in reducing sugar (as glucose) when CD was incubated at 37℃ for 4 h with crude enzyme preparations. Cyclodextrinase activity was predominantly cell bound and induced in both organisms by growth on CD. Analysis via high performance liquid chromatography showed that products of CD hydrolysis by the crude enzyme preparations from the 2 strains were sharply different. B. ovatus 3524 cyclodextrinase yielded glucose only, while the B. distasonis Cl8-7 enzyme catalyzed production of a series of maltooligomers. Cyclodextrinase of both strains was stable at 4℃ for at least 48 h. B. distasonis Cl8-7 cyclodextrinase showed greater than 75% retention of activity at temperatures up to 55℃ after 48 h, whereas the B. ovatus 3524 enzyme was labile above 25℃. Optimum activity and stability of cyclodextrinase from both strains occured at pH 7.0.

Salt precipitation and chromatographic methods were utilized in an attempt to purify the enzyme(s) in crude cyclodextrinase. No enzymes were purified to homogeneity, but a 15- to 17-fold increase in specific cyclodextrinase activity was obtained via hydrophobic interaction chromatography. Also, the products obtained by the action of cyclodextrinase from B. ovatus 3524 were markedly altered during purification, suggesting that the crude cyclodextrinase contains a mixture of enzymes.