BIOAVAILABILITY OF NEW SYNTHESIZED GLUCOOLIGOSACCHARIDES IN THE INTESTINAL-TRACT OF GNOTOBIOTIC-RATS

Using germ-free rats and previously germ-free rats inoculated with a c omplex human flora (heteroxenic rats), the digestibility of new glucoo ligosaccharides (GOS) and the effect of the digestive flora on their f ermentation were studied. The GOS were synthesized using a glucosyltra nsferase reaction and were composed of a mixture of mono- to heptasacc harides (degree of polymerisation (DP) from 1 to 7), with alpha-1,6 an d alpha-1,2 linkages. In germ-free rats, two diets containing GOS (20 g kg-1 diet and 40 g kg-1 diet) were compared to a control diet contai ning sucrose. The extent of GOS digestion was about 20 % and the major component, DP 5, was almost fully resistant to the action of endogeno us enzymes. In heteroxenic rats, only GOS (20 g kg-1 diet) was compare d to the control diet. Gaseous H-2 and CH4 excretions measured in a re spiratory chamber significantly increased by GOS fermentation (1.8 and 2.9 times, respectively, P < 0.001). As compared to the control group , there were no modifications of the pH, short-chain fatty acids (SCFA ), and lactic acid concentrations in the caecum of rats fed with the G OS diet, but there were changes of the SCFA profile, ie butyric, isobu tyric and isovaleric acid proportions significantly decreased (P < 0.0 1), whereas the caproic acid proportion increased (P < 0.05). GOS appe ared to be completely fermented. Changes in the gaseous excretion and in the SCFA profile suggest that the intake of a low amount of this ne w synthetised GOS led to some decrease in the proteolytic activity and in an enhancement of the glycolytic fermentation.