A mucin-enriched fermentation model to assess prebiotic potential of new indigestible carbohydrates

Screening the prebiotic potential of novel indigestible carbohydrates (ICH) is a challenge for feed and food industry and in vitro models are increasingly used for such purposes. Recently extracellular binding proteins responsible for the adherence to intestinal mucus were described for several Lactobacillus species. As this genus is known for its beneficial effect on gut health, we enriched the in vitro gas fermentation model with mucin in order to evaluate the prebiotic potential of 5 ICH. Mucin-coated microcosms (MCM) were prepared as described by Van den Abbeele et al. (2012, Microbial Biotechnology, 5, 106-115) and introduced in the fermentation bottles with an inoculum prepared from fresh faeces of 3 sows mixed with a nutritive buffer solution. Fermentation was performed at 39°C, using 200 mg of substrate, 30 ml of inoculum and 6 MCM, yielding approx. 20 mg mucin each, in 140 ml glass bottles. A first study was performed with inulin and cellulose as substrates, with and without mucus in the bottles. A second study was performed with 5 substrates (inulin, IMO, beet pulp POS, cellobiose and gluconate) in presence of mucus. After 8 and 72h, SCFA and the microflora of fermentation broth was analysed as well as the microflora on the MCM. The comparison of the microflora evolution with and without mucus showed a better development of the Lactobacillus in the fermentation broth, mainly in presence of inulin. The development of the Lactobacillus genus allowed the classification of the 5 substrates tested in the second study (Inulin > IMO > Gluconate > Cellobiose > POS)(P < 0.05) which was not possible without mucus (P > 0.05). Inulin and IMO showed also the highest development of Bifidobacteria (P < 0.05) and the highest levels of butyrate production (P < 0.05) compared to the three other substrates, indicating a high prebiotic potential.