In vitro fermentation characteristics of a mixture of Raftilose and guar gum by human faecal bacteria

Abstract

The therapeutic effects of indigestible carbohydrates in the human colon are well known. Most fermentation studies have examined only single carbohydrates. Considering the idiosyncratic actions of individual carbohydrates and the dose required, it is unlikely that any one carbohydrate will provide ideal physiological actions without having some undesirable effects. Little is known of how mixing non-digestible carbohydrates affects their fermentation. This necessitates fermentation studies using different carbohydrates in mixtures. The aim of this study was to test the effect of mixing Raftilose (R) and guar gum (G) on short chain fatty acid (SCFA) production in in vitro cultures of human faecal bacteria. The fermentation of the individual carbohydrates (10 mg/ml) was compared with that of a 50:50 mixture in anaerobic in vitro cultures of human faeces. Cultures of R/G mixtures produced significantly more n-butyrate than 100 mg G alone at 8 and 24 hours (p < 0.02). There was no significant difference in the production of n-butyrate between cultures of 100 mg R and the R/G mixture at 8 and 24 hours. R (100 mg) produced a propionic/butyric (p/b) acid ratio of 1.18 compared with 3.88 for 100 mg G, whereas R/G mixture produced a p/b ratio of 2.01. The fermentation of R/G mixture was different compared with 100 mg of R or G alone. There was no loss of n-butyrate in the culture containing R/G (50 mg of each) mixture compared with the 100 mg R culture.