Kinetic analyses of bacterial growth, carbohydrate consumption, and metabolite production of five butyrateproducing clostridial cluster XIVa colon bacteria grown on acetate plus fructose, oligofructose, inulin, or lactate were performed. A gas chromatography method was set up to assess H 2 and CO 2 production online and to ensure complete coverage of all metabolites produced. was the only strain included in the present study that was able to grow on fructose, oligofructose, and inulin. The metabolites produced were lactate, butyrate, and CO 2 , without H 2 production, indicating an energy metabolism distinct from that of other Roseburia species. Oligofructose degradation was nonpreferential. In a coculture of R. inulinivorans DSM 16841 T with the highly competitive strain Bifidobacterium longum subsp. longum LMG 11047 on inulin, hardly any production of butyrate and CO 2 was detected, indicating a lack of competitiveness of the butyrate producer. Complete recovery of metabolites during fermentations of clostridial cluster XIVa butyrate-producing colon bacteria allowed stoichiometric balancing of the metabolic pathway for butyrate production, including H 2 formation.