[Use of the gnotobiotic rat for determination of the in vivo activity of Bifidobacterium beta-galactosidase].

Under the conditions of in vitro cultivation, the height of the beta-galactosidase activity of Bifidobacterium spec. is essentially influenced by the composition of the culture medium. The use of gnotobiotic (germ-free and monoassociated with Bifidobacterium longum) rats permitted to differentiate in the chyme between beta-galactosidase activities of mucosal and microbial origin. In germ-free animals, the chyme in the small intestine and the colon contains nearly 10-20% of the activity measured in the mucosa (in each case expressed as g on a wet-weight basis). Monoassociation with B. longum does not affect the lactose-splitting activity of the chyme in the small intestine, but increases the activity of the chyme in the colon to twice the value of the mucosal activity. In the monoassociated animals, feeding of lactose leads to a further multiple increase of the chymal beta-galactosidase activity in the caecum, colon and faeces.