Wheat bran thermal treatment in a hot air oven does not affect the fermentation and colonisation process by human faecal microbiota

Wheat bran, rich in dietary fibre, serves as an important fermentation substrate and provides a unique colonisation site for the human gut microbiota. Dry heat treatment is frequently applied to stabilise wheat bran by inactivating endogenous enzymes that otherwise cause rancidity. It, however, alters wheat bran surface properties, which might affect wheat bran colonisation and fermentation, possibly interfering with the production of health promoting microbial metabolites. We found that the heat-induced increased bran surface hydrophobicity was obliterated during in vitro gastrointestinal digestion. As a consequence, the prebiotic action was preserved during in vitro batch incubations with faecal microbiota from ten healthy individuals. The microbial community both in suspension and colonising the insoluble wheat bran residue, remained unaffected and sustained a similar microbial activity compared to unmodified wheat bran. The wheat-bran attached and luminal community differed significantly, confirming our previous results and this was unaffected by dry heat-treatment.