Partial characterization of bifidobacterium breve C50 cell-free whey compounds inducing modifications to the intestinal microflora.

Cell-free whey obtained from milk fermented with Bifidobacterium breve C50 (Bb C50) has been shown to modify the intestinal flora in humans and mice. Previous work showed that no antibiotic-like or barrier effect due to overgrowing bifidobacteria was implied in the microbial modifications. The present study was focused on characterizing the compounds and mechanisms involved. Protein, sugar, and enzymatic profiles of Bb C50 whey were therefore determined and compared to those of a whey unable to modify the intestinal flora of humans and mice. No remarkable difference was noted except for a higher lactosidase activity in Bb C50 whey. Various physical treatments were then applied to fractions of Bb C50 whey. Activity was assessed in C3H mice by analyzing changes in the intestinal flora balance throughout a 15-d administration of each treated whey. Heating at 80 degrees C and aerobic storage for 2 wk completely abolished Bb C50 whey activities. In contrast, the addition of a reducing agent (cysteine hydrochloride), either at the beginning of a 15-d aerobic storage or prior to administration, as well as preserved these activities. Susceptibility to heating and oxidation suggested that an enzyme might play a role in the induced microbial changes. Since the Bb C50 lactosidase was partly inactivated by the oxidative treatment, it could support the in vivo activity. The enzyme might reach the intestinal lumen and partly degrade substrates, such as mucins, usually used by the intestinal flora. The released molecules might then favor the development of a new microbial balance.

Identification and synthesis of a trisaccharide produced from lactose by transgalactosylation.

Enzymatic transgalactosylation of lactose by means of Streptococcus thermophilus, subspecies DN-001065, led to a mixture of D-galactose (approximately 4%), D-glucose (approximately 15%), lactose (approximately 51%), minor disaccharides (6%), trisaccharides (approximately 20%) and tetrasaccharides (3%). The major trisaccharide (approximately 16%) was identified by NMR spectroscopy and chemical synthesis as being the known beta-D-galactopyranosyl-(1-->3)-beta-D-galactopyranosyl-(1-->4)-D-glucos e (3'-beta-D-galactopyranosyl-lactose). It was purified from a mixture of peracetylated oligosaccharides by column chromatography followed by deacetylation. For the first time, 3'-beta-D-galactopyranosyl-lactose has been obtained on the 1 g scale, by resorting to simple techniques and equipment. NMR spectra have been unambiguously assigned.