MICROBIAL ECOLOGY IN HEALTH AND DISEASE VOL. 2: 29-36 (1 989) The in vivo Effect of Dietary Buffering Capacity on the Bifidogenic Activity of Human Milk Oligosaccharides

The buffering capacity of a milk diet is known to be involved in the control of a newborn's bifidobacterial flora. Other factors could modulate the bifidobacterial flora e.g. bifidus factors present in human milk, which are growth-promoting for Bi3dobacterium bi$durn. The aim of this study was to investigate in gnotobiotic mice the effects of human milk bifidus factors upon colonis-ation by bifidobacteria according to the dietary buffering capacity. A high buffering capacity diet encouraged the implantation of higher numbers of bifidobacteria in monoxenic mice than a low buffering capacity one. However, supplementary feeding with human milk oligosaccharides (gynolactose) did not support the proliferation of B. bijdum, although the gynolactose bifidus factors were not destroyed during digestion. Furthermore the addition of gynolactose to a high buffering capacity diet led to the breakdown of some of the intestinal glycoproteins detected in the bifidogenic extract of stools from germfree mice. In addition, although the human milk oligosaccharides stimulated the excretion of intestinal bifidus factors when supplementing a low buffering capacity diet, they failed to do so on a high buffering capacity diet. These results suggest that the ability of human milk oligosaccharides to encourage the proliferation of B. bijidum depends upon their capacity to stimulate intestinal bifidus factors. This capacity seemed to be related to the buffering capacity of the diet. KEY woms-Bifidobacterium bifidum; Gynolactose; Germ free mice: Intestinal mucus