The effect of insoluble wheat fibers consisting of cellulose and hemicellulose on the activity and composition of a pooled active human microbiota of healthy adult individuals in an in vitro model of the proximal human colon.

The fermentability of test products, being two types of extrinsic, water-insoluble wheat fibres named WF600 and WF101, suitable for food fortification, was studied in the in vitro system TIM-2 in comparison with inulin. The TIM-2 system, mimicking the human proximal colon, contains the complex human gut microbiota that is metabolically active and composed of a pool of fecal microbiota of 5 healthy adult individuals. The effect of the test products on the production of short-chain fatty acids and ammonia was determined. In addition, effects on microbiota composition was determined at start and after 72 hours by 16S rDNA amplicon sequencing in the Illumina MiSeq system. The Wheat fibres were shown to be fermentable, like inulin, but resulted in a different fermentation profile. The genus Ruminococcus was shown to be able to access complex wheat fibre structures, and contributed largely to changes in microbiota composition in the presence of wheat fibre. The study proved that the tested insoluble wheat fibres have prebiotic properties.