Probiotic low-fat fermented goat milk with passion fruit by-product: In vitro effect on obese individuals’ microbiota and on metabolites production

In Vitro Simulation of Human Colonic Fermentation: A Practical Approach towards Models’ Design and Analytical Tools

“…These simulators have different designs so that the fermentation process can include a single (mono-stage) or several compartments (multi-stage). While only a segment of the colon is simulated (i.e., the proximal colon which is considered as ascendant and transversal) in mono-stage systems [62][63][64], dynamic multi-stage models can simulate up to the three regions of the colon: the ascending, transverse, and descending colon, reproducing the different in vivo environmental conditions (in terms of pH, retention time, characteristic volume, and availability of substrates) in each of them [65][66][67]. Moreover, some of the dynamic in vitro models also include compartments to simulate part of the upper gastrointestinal digestion: gastric and small intestine [68,69] or a dialysis system, which simulate the absorption of the metabolites produced during the fermentation process [62].…”

“…Altogether, dynamic models allow for the study of the effects of food on gut microbiota in a more complex environment that simulates the in vivo conditions better than static models and allow for the assessment of longer periods of time (e.g., one or several weeks) [61,65,66]. The main research objectives when using these models have been the evaluation of the prebiotic, probiotic, and symbiotic effect of some compounds on gut microbiota: Table 2 gathers the objectives and references of published studies reporting the applicability of dynamic colonic models in food science and technology fields over the last 10 years.…”

“…[ 65,67,70,71,[90][91][92] Other applications assessing the effect of: -Food ingredients (e.g., Mexican "taco" from corn tortilla and black beans).…”

“…Then, the suspension is manually homogenised or is homogenised using a stomacher [31,36,43,56,69]. In addition to the previous homogenisation stage, some protocols include filtering [27,30,54], or centrifugation steps [37,65,80] so that the supernatant is used as faecal inoculum in the fermentation process. In addition, other protocols include the extraction of the bacterial mass from the rest of the components of the faecal sample by means of the use of iohexol (Nycodenz ® ), which is added to the supernatant of a previously homogenised faecal suspension, causing the isolation of viable cells.…”

“…When it comes to metabolite analysis, SCFA or BCFA production are typically analysed using gas or liquid chromatography (GC or LC) coupled with either different detectors (e.g., FID or UV) or MS [43,54,56], but when other metabolites, such as phenolic compounds, are being considered in the studies, LC techniques coupled with MS [44,102] or antioxidant tests are commonly used when studying antioxidant capacity [33]. Finally, ammonium, pH, lactic acid, and gas volume measurements are also analysed in most of the studies [36,65,71]. Table 3 collects different analytical techniques that usually applied in in vitro gut fermentation studies.…”