METABOLIC PATHWAYS OF HUMAN MICROBIOTA CO-UTILIZATION OF FIBRES AND COLONIC MUCINS

The human gut microbiota is crucial for degrading dietary fibres from the diet. However, some of these bacteria can also degrade host glycans, such as mucins, the main component of the protective gut mucus layer. Specific microbiota species and mucin degradation patterns are associated with inflammatory processes in the colon. Yet, it remains unclear how the utilization of mucin glycans affects the degradation of dietary fibres by the human microbiota. Here, we used dietary fibres and oligosaccharides to study in vitro the dynamics of mucin and dietary fibre degradation by the human faecal microbiota. Three dietary fibres (apple pectin, beta-glucan and xylan) showed clearly distinguishing modulatory effects on faecal microbiota composition. The utilization of mucin in cultures led to alterations in microbiota composition and metabolites. Co-metabolism of mucin and complex dietary fibres promoted formation of mixed acids and biogenic amines which have been shown to be beneficial to the host. Interestingly, the metaproteome analysis showed the central role of the Bacteroides in degradation of complex fibres while Akkermansia muciniphila was the main degrader of porcine colonic mucin but not gastric mucin. This work demonstrates the intricacy of complex glycan metabolism by the gut microbiota and how the utilization of host glycans leads to alterations in the metabolism of dietary fibres.