In vitro kinetics of prebiotic inulin-type fructan fermentation by butyrate-producing colon bacteria: implementation of online gas chromatography for quantitative analysis of carbon dioxide and hydrogen gas production.

Kinetic analyses of bacterial growth, carbohydrate consumption, and metabolite production of five butyrate-producing 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 H2 and CO2 production online and to ensure complete coverage of all metabolites produced. Method accuracy was confirmed through the calculation of electron and carbon recoveries. Fermentations with Anaerostipes caccae DSM 14662(T), Roseburia faecis DSM 16840(T), Roseburia hominis DSM 16839(T), and Roseburia intestinalis DSM 14610(T) revealed similar patterns of metabolite production with butyrate, CO2, and H2 as the main metabolites. R. faecis DSM 16840(T) and R. intestinalis DSM 14610(T) were able to degrade oligofructose, displaying a nonpreferential breakdown mechanism. Lactate consumption was only observed with A. caccae DSM 14662(T). Roseburia inulinivorans DSM 16841(T) 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 CO2, without H2 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 CO2 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 H2 formation.