Inulin-type fructan degradation capacity of interesting butyrate-producing colon bacteria and cross-feeding interactions of Faecalibacterium prausnitzii DSM 17677 ^T with bifidobacteria

Abstract

Background Inulin-type fructans have already been studied with respect to their stimulation of bifidobacteria and butyrate-producing colon bacteria, such as Anaerostipes caccae and Roseburia spp. However, much less is known about their effects on other butyrate-producing colon bacteria, such as Butyricicoccus pullicaecorum, Eubacterium spp. and Faecalibacterium prausnitzii and the interactions of these species with bifidobacteria. This study aimed at investigating the kinetics of inulin-type fructan degradation and organic acid and gas production by B. pullicaecorum DSM 23266T, E. hallii L2-7, E. rectale CIP 105953T, and F. prausnitzii DSM 17677T and the possible interactions between F. prausnitzii DSM 17677T and bifidobacteria. Materials and methods All butyrate-producing strains were studied during screening experiments (100-ml scale) and monoculture fermentations (1.5-l scale) in a medium for colon bacteria (MCB) containing either fructose, oligofructose, or long-chain inulin as an energy source, supplemented with acetate. Coculture fermentation experiments (1.5-l scale) in MCB were performed with F. prausnitzii DSM 17677T and Bifidobacterium breve Yakult, Bifidobacterium adolescentis LMG 10734, Bifidobacterium angulatum LMG 11039T (oligofructose), and Bifidobacterium longum LMG 11047 (oligofructose or inulin as a substrate). Results Butyricicoccus pullicaecorum DSM 23266T and E. hallii L2-7 degraded fructose only, resulting in the production of butyrate, H2 and CO2. Eubacterium rectale CIP 105953T produced lactate and butyrate as well as H2 and CO2 out of fructose and inulin-type fructans. Faecalibacterium prausnitzii DSM 17677T produced butyrate, formate, and traces of lactate, together with CO2 out of fructose, oligofructose, and inulin. Both oligofructose-consuming, butyrate-producing strains degraded all oligofructose fractions simultaneously, indicating an extracellular degradation mechanism. During coculture fermentation experiments, oligofructose (by all bifidobacteria, except for B. breve Yakult) and inulin (by B. longum LMG 11047) were converted into acetate, lactate, and formate. Faecalibacterium prausnitzii DSM 17677T was cross-fed on this acetate resulting in the production of its metabolites. However, only low amounts of butyrate were produced during the coculture fermentations with B. angulatum LMG 11039T and B. longum LMG 11047, since F. prausnitzii DSM 17677T did not manage to compete well for the oligofructose substrate in the presence of B. angulatum LMG 11039T and B. longum LMG 11047, and for the inulin substrate in the presence of B. longum LMG 11047. Conclusion Besides cross-feeding interactions between bifidobacteria and butyrate-producing colon bacteria, competition for the available inulin-type fructans between these colon bacteria may occur. As a result, fast degraders such as bifidobacteria are favoured compared to acetate-depending butyrate producers.