摘要：Bifidobacterium sp. strain SEN was isolated and characterized by hydrolytic conversion of sennosides to sennidins (Akao et al., Appl. Environ. Microbiol., 60, 1041 (1994)). The sennoside-hydrolyzing capacity of the strain SEN was disappeared following the addition of glucose to the media in spite of good bacterial growth and potent activity hydrolyzing p-nitrophenyl β-D-glucopyranoside (pNPG). In a fructose-containing medium, no such suppressing effect was shown. Following a 10 h incubation in 50 mM potassium phosphate buffer (pH 7.4), the sennoside-hydrolyzing activity of the bacterium increased, dose-dependently, with the addition of sennoside B. Inhibition of the substrate-induced increase in sennoside-hydrolyzing activity was observed following the addition of some antibiotics (chloramphenicol, streptomycin, and rifampicin). In particular, chloramphenicol completely inhibited the increase of sennoside-hydrolyzing activity while 38% pNPG-hydrolyzing activity remained. It is suggested that the strain SEN produces two different β-glucosidases of which the sennoside-hydrolyzing enzyme is inducible. In addition, the glucosides pNPG, esculin, salicin, or amygdalin stimulated the induction of the sennoside β-glucosidase, but less markedly than sennoside. Sennidin A or sugars (glucose, fructose, cellobiose, or maltose) did not induce the enzyme.
