Effect of inulin on the human gut microbiota: stimulation ofBifidobacterium adolescentisandFaecalibacterium prausnitzii

Abstract

Prebiotics are food ingredients that improve health by modulating the colonic microbiota. The bifidogenic effect of the prebiotic inulin is well established; however, it remains unclear which species ofBifidobacteriumare stimulatedin vivoand whether bacterial groups other than lactic acid bacteria are affected by inulin consumption. Changes in the faecal microbiota composition were examined by real-time PCR in twelve human volunteers after ingestion of inulin (10 g/d) for a 16-d period in comparison with a control period without any supplement intake. The prevalence of most bacterial groups examined did not change after inulin intake, although the low G+C % Gram-positive speciesFaecalibacterium prausnitziiexhibited a significant increase (10·3 % for control periodv.14·5 % during inulin intake,P = 0·019). The composition of the genusBifidobacteriumwas studied in four of the volunteers by clone library analysis. Between three and fiveBifidobacteriumspp. were found in each volunteer.Bifidobacterium adolescentisandBifidobacterium longumwere present in all volunteers, andBifidobacterium pseudocatenulatum,Bifidobacterium animalis,Bifidobacterium bifidumandBifidobacterium dentiumwere also detected. Real-time PCR was employed to quantify the four most prevalentBifidobacteriumspp.,B. adolescentis,B. longum,B. pseudocatenulatumandB. bifidum, in ten volunteers carrying detectable levels of bifidobacteria.B. adolescentisshowed the strongest response to inulin consumption, increasing from 0·89 to 3·9 % of the total microbiota (P = 0·001).B. bifidumwas increased from 0·22 to 0·63 % (P < 0·001) for the five volunteers for whom this species was present.