Prebiotics are defined as non-digestible food ingredients that selectively stimulate health-promoting bacteria in the gut microbiome. A key feature of prebiotics is their resistance to upper gastro-intestinal digestion so that they reach the colon where they are fermented by the gut microbiome.
Fructans, such as fructooligosaccharides (FOS) and inulin are considered to be “gold standard” prebiotics, with human clinical trials supporting their beneficial effect in acute and chronic diseases such as obesity and type 2 diabetes (T2D), allergy, inflammatory bowel disease (IBD), Traveler’s diarrhea and constipation (an overview is given in).
Although critical to the definition of potential prebiotic ingredients, studies confirming the indigestibility of studied prebiotic ingredients are scarce. Many studies have been limited to descriptive analysis of faecal samples as in situ samples from the site of fermentation are difficult to obtain, according to the current report.
In this study, researchers from ProDigest BV, in Belgium (a spin-off company from the Laboratory of Microbial Ecology and Technology), investigated whether ‘cRG-I’, carrot-derived RG-I enriched extract, could be a potential prebiotic ingredient.
The team used novel in vitro models simulating the human colonic environment coupled with cell-based assays mimicking the host gut barrier in order to prove the ingredient’s non-digestibility and outline which specific health benefiting bacteria are stimulated.
The report states: “cRG-I displays unique properties as it was fermented more rapidly than inulin leading to production of SCFA, especially acetate and propionate, and less gas than inulin.
“It increases the abundance of several bacterial species reputed for their “anti-inflammatory” profile. In line with this, the metabolites resulting from cRG-I fermentation exhibited a protective effect in an in vitro model of inflamed gut barrier.
“Overall, the data obtained during this study support future research to further investigate this novel prebiotic candidate in long-term SHIME models with different fecal sample donors and in clinical trials to confirm the beneficial effect of cRG-I on the microbiota and its impact on human health.”
A novel in vitro model (M-SHIME; Mucosal Simulator of the Human Intestinal Microbial Ecosystem) was recently developed as a complementary in vitro tool. In this model, the mucosal microbiota was enriched with butyrate-producing Clostridium cluster XIVa members, correlating with in vivo findings from biopsies.
In the current study, first, the team demonstrated the non-digestibility of the carrot derived extract in the upper gastro-intestinal tract using host-derived amylases and brush border enzymes and compared its digestibility to starch (digestible) and inulin (non-digestible), and confirmed it was comparable to inulin.
Next, a 48 hour colonic incubation revealed that cRG-I fermentation increased levels of health-promoting short-chain fatty acids (mainly acetate and propionate) and lactate, comparable to inulin.
To discover the specific bacterial strains promoted by the ingredient, they added a mucosal environment while applying quantitative 16S-targeted Illumina sequencing.
The team found that growth was promoted for a number of health promoting bacteria: Bifidobacterium longum, Bifidobacterium adolescentis, Bacteroides dorei, Bacteroides ovatus, Roseburia hominis, Faecalibacterium prausnitzii, and Eubacterium hallii.
The team also found that the fermented ingredient increased barrier integrity while decreasing markers for inflammation.
Mercenier. A., et al
A Novel Non-Digestible, Carrot-Derived Polysaccharide (cRG-I) Selectively Modulates the Human Gut Microbiota while Promoting Gut Barrier Integrity: An Integrated in Vitro Approach