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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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Chito-oligosaccharides (COS) are being used as important functional materials for many applications due to their bioactivities. The aim of this research has been to assess the relationship between the physico-chemical characteristics, average molecular weight (Mw), acetylation degree (DA), polymerization degree (DP) and specially sequence composition determined by MALDI-TOF MS and the antioxidant properties of COS. These oligosaccharides were obtained by enzymatic depolymerization with chitosanase and lysozyme using a specific chitosan and its reacetylated product. The COS fraction below 5 kDa obtained from chitosanase depolymerization showed the highest capacity to scavenge DPPH radicals and to reduce Fe(3+). A correlation was found between the relative amount of molecules with a given A/D (acetylated vs deacetylated units) ratio within the COS and their antioxidant activity, which could be used to predict the antioxidant behavior of a fraction of chito-oligosaccharides., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Graphical abstract Highlights • Chitosanolytic activity was extracted from the biopesticide B. subtilis var. aizawai. • The chitosanolytic activity isolated was of the endo-type. • Reaction products were a mixture of deacetylated chitooligosaccharides (DP 2–5). • Chitosan was fully converted into oligosaccharides. Abstract Starting from a commercial preparation of Bacillus thuringiensis var. aizawai , widely employed as biopesticide in agriculture, we obtained a chitosanolytic activity by washing the cells with concentrated sodium acetate. The optimum pH and temperature values for this enzyme were 6.0 and 60 °C, respectively. The enzymatic extract efficiently hydrolyzed various chitosans with different deacetylation degrees (DD) into small oligosaccharides. Combining mass spectrometry (ESI-Q-TOF) and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), we observed the formation of fully deacetylated chitooligosaccharides [ fd COS, (GlcN) 2-5 ] and, to a lesser extent, partially acetylated chitooligosaccharides [ pa COS, GlcNAc-(GlcN) 1-3 ]. A 10 g/L solution of chitosan with 600–800 kDa and DD ≥ 90% was fully converted into oligosaccharides in 55 h. Most of the products were fd COS: 1.6 g/L of chitobiose, 1.7 g/L of chitotriose, 5 g/L of chitotetraose and 1.4 g/L of chitopentaose. [ABSTRACT FROM AUTHOR]