In Vitro prebiotic effects of Acacia gums onto the human intestinal microbiota depends on both botanical origin and environmental pH

Acacia gums are commonly used food additives. It is currently unclear how e xtensively these non-digestible polysaccharides are fermented in the human large intestine. However, they have been shown to support bifidobacterial g rowth in vitro and may represent useful candidate prebiotics. In these inve stigations, in vitro 24-h batch incubations and chemostat continuous-cultur es of human faecal bacteria were conducted using two acacia gums (Fibregum standard and Fibregum AS(R)). Our aim was to study the effects of these gum s on bacterial ecology and fermentation in the large bowel. Fructooligosacc harides (Actilight(R)-950P) were also investigated as a reference. Both Acacia gums were extensively fermented by intestinal flora although th ere were marked differences in fermentation product formation and ecologica l effects, probably due to their differing botanical origins and/or biochem ical characteristics. In particular, fermentation of Fibregum AS(R) led to significantly higher proportions of propionate both in batch and chemostat experiments. Both gums decreased Clostridium sp. levels but only Fibregum-s tandard induced higher Lactobacillus sp. counts compared to control. These bacterial modifications were highly dependant of the operating pH of the fe rmentation system with acidic conditions promoting both the prebiotic and t he butyrogenic effects of fructooligosaccharides. In these studies, we have demonstrated that, similarly to fructooligosaccha rides, Acacia gums can exert putatively beneficial effects on host health t hrough both the improvement of the composition of the large intestine micro flora and SCFA formation. (C) 1998 Academic Press.