Effect of chito-oligosaccharides over human faecal microbiota during fermentation in batch cultures

• Mw and DA of COS are determinant factors for in vitro fermentability.
• Very deacetylated COS might decrease some human microbiota populations.
• COS with many acetylated residues maintain human microbiota populations.
• COS with many acetylated residues could increase Lactobacillus/Enterococcus.

Chitosan with high number of deacetylated units, its reacetylated derivative and COS obtained through an enzymatic treatment with chitosanase were tested in pH controlled batch cultures to investigate the ability of the human faecal microbiota to utilise them.Chitosan derivatives with high number of deacetylated units decreased the bacterial populations: Bifidobacterium spp., Eubacterium rectale/Clostridium coccoides, C. Histolyticum and Bacteroides/Prevotella. On the other hand, chitosan derivatives with high content of acetylated residues maintained the tested bacterial groups and could increase Lactobacillus/Enterococcus. Regarding short chain fatty acids (SCFA), only low Mw COS increased the production in similar levels than fructo-oligossacharides (FOS). The acetylated chitosans and their COS do not appear as potential prebiotics but did not affect negatively the faecal microbiota, while derivatives with high number of deacetylated units could induce a colonic microbiota imbalance.