Bifidobacterial inulin-type fructan degradation capacity determines cross-feeding interactions between bifidobacteria and Faecalibacterium prausnitzii

• Bifidobacteria cross-feed acetate to Faecalibacterium prausnitzii DSM 17677T.
• Acetate enables F. prausnitzii DSM 17677T to degrade oligofructose and inulin.
• Cross-feeding interactions depend on the bifidobacterial strains involved.
• These interactions can be a commensal beneficial relationship between the bacteria.
• Commensal cross-feeding interactions can be dominated by competition.

Prebiotic inulin-type fructans (ITF) display a bifidogenic and butyrogenic effect. Four bifidobacterial strains (Bifidobacterium breve Yakult, Bifidobacterium adolescentis LMG 10734, Bifidobacterium angulatum LMG 11039T, and Bifidobacterium longum subsp. longum LMG 11047), displaying different ITF degradation capacities, were each grown in cocultivation with Faecalibacterium prausnitzii DSM 17677T, an ITF-degrading butyrate-producing colon bacterium, as to unravel their cross-feeding interactions. These coculture fermentations were performed in a medium for colon bacteria, whether or not including acetate (necessary for the growth of F. prausnitzii DSM 17677T and whether or not provided through cross-feeding), supplemented with oligofructose or inulin as the sole energy source. Bifidobacterium breve Yakult did not degrade oligofructose, resulting in the production of high concentrations of butyrate by F. prausnitzii DSM 17677T through oligofructose degradation. The degradation of oligofructose by B. adolescentis LMG 10734 and of oligofructose and inulin by B. angulatum LMG 11039T and B. longum LMG 11047 resulted in the production of acetate, which was cross-fed to F. prausnitzii DSM 17677T, enabling the latter strain to degrade oligofructose and inulin. Slow preferential degradation of the short chain length fractions of oligofructose (intracellularly) by B. adolescentis LMG 10734 enabled substantial oligofructose degradation by F. prausnitzii DSM 17677T. However, fast non-preferential degradation of all chain length fractions of oligofructose (extracellularly) and efficient degradation of the short chain length fractions of inulin by B. angulatum LMG 11039T and B. longum LMG 11047 made it impossible for F. prausnitzii DSM 17677T to compete for the available substrate. These results indicate that cross-feeding interactions between bifidobacteria and acetate-depending, butyrate-producing colon bacteria can be either a pure commensal or beneficial relationship between these bacteria, or can be dominated by competition, depending on the ITF degradation capacities of the bifidobacterial strains involved.