Structurally different galacto-oligosaccharides have different digestibility patterns and bifidogenic properties in rats

Resumen del trabajo presentado al 20th International Congress of Nutrition, celebrado en Granada (España) del 15 al 20 de septiembre de 2013.[Background and objectives]: Galacto-oligosaccharides (GOS) have demonstrated to increase the bifidobacterial population of fecal microbiota in healthy human's volunteers; however, such effect was not observed in other related studies. These dissimilarities can be attributed to several factors including the type, purity and composition of the GOS used. The relationship between bifidogenic properties and structural features of GOS in vivo has been investigated. [Methods]: A comparative study regarding the resistance to gut digestion, fermentability and selective growth of beneficial bacteria in the large intestine of rats fed novel GOS derived from lactulose (GOS-Lu) or commercially available derived from lactose (GOS-La) was carried out. Animals were fed either a control diet or diets containing 1% (w/w) of GOS-Lu or GOS-La for 14 d; Cr2O3 was included in diets as an indigestible marker. [Results]: Quantitative analysis of carbohydrates from dietary and ileal samples demonstrated that the trisaccharide fraction of GOS-Lu was significantly more resistant to gut digestion than that from GOS-La, according to their ileal digestibility rates (12.5 and 52.9%, respectively), whilst the disaccharide fraction of GOS-Lu was fully resistant. The low ileal digestibility of GOS-Lu was attributed to the great resistance of galactosyl-fructoses to mammalian digestive enzymes, highlighting the key role played by monomer composition and linkage type involved in the oligosaccharide chain. The absence of GOS-La and GOS-Lu digestion-resistant oligosaccharides in fecal samples indicated that they were readily fermented within the large intestine, enabling both GOS to have a potential prebiotic function. The novel GOS-Lu exerted a stronger bifidogenic effect on gut microbiota than GOS-La, having the former a selective and significant increase of Bifidobacterium animalis. [Conclusions]: A direct relationship between patterns of resistance to digestion and bifidogenic properties of galactooligosaccharides is revealed.Peer Reviewe