Galacto-oligosaccharides derived from lactulose exert a selective stimulation on the growth of Bifidobacterium animalis in the large intestine of growing rats.

There is increasing interest in identifying novel dietary nondigestible carbohydrates capable of modulating the composition and/or metabolic activities of the gut microbiota. This work assessed the differential modulatory influence of novel galacto-oligosaccharides derived from lactulose (GOS-Lu) in comparison with commercial galacto-oligosaccharides derived from lactose (GOS-La) in gut microbiota of growing rats (5 weeks old). Rats were fed either a control diet or diets containing 1% (w/w) of GOS-Lu or GOS-La, and cecal and colonic contents were collected after 14 days of treatment. Compared to controls, GOS-Lu had significantly more bifidobacteria within the large intestine, showing a significant and selective increase of Bifidobacterium animalis in the cecum and colon; however, no significant differences in the number of bifidobacteria among GOS-Lu and GOS-La groups were observed. Both types of GOS significantly increased the number of the Eubacterium rectale / Clostridium coccoides group. These findings support a prebiotic role of galactosyl-fructoses in functional foods.