Estimation and interpretation of fermentation in the gut: coupling results from a 24 h batch in vitro system with fecal measurements from a human intervention feeding study using fructo-oligosaccharides, inulin, gum acacia, and pea fiber.

Gut bacteria ferment fiber at different rates to primarily short chain fatty acids (SCFA) and gas while proteins are metabolized to SCFA, branched chain fatty acids (BCFA), gas, and undesirable metabolites. Large volumes of gas produced in vivo may contribute to bloating and flatulence in an individual. The objectives of this trial were to (1) compare the in vitro fermentation profiles of fructo-oligosaccharides (FOS), inulin, gum acacia, and pea fiber alone or blended using a 24 h batch model and (2) relate these findings to a human study that fed enteral formula fortified with fiber blend (FB) or no fiber (FF). The in vitro fermentation of the fiber blend resulted in a delayed pH decrease and gas and SCFA production compared to the FOS and inulin. Human samples had higher SCFA on FB compared to FF (p = 0.029). BCFA were not different between formulas. By using a blend of fibers, we observed a slower fermentation in vitro but still increased fecal SCFA when fed to human subjects.

Fermentation profiles of wheat dextrin, inulin and partially hydrolyzed guar gum using an in vitro digestion pretreatment and in vitro batch fermentation system model.

This study investigated the fermentation and microbiota profiles of three fibers, wheat dextrin (WD), partially hydrolyzed guar gum (PHGG), and inulin, since little is known about the effects of WD and PHGG on gut microbiota. A treatment of salivary amylase, pepsin, and pancreatin was used to better physiologic digestion. Fibers (0.5 g) were fermented in triplicate including a control group without fiber for 0, 4, 8, 12, and 24 h. Analysis of pH, gas volume, hydrogen and methane gases, and short chain fatty acid (SCFA) concentrations were completed at each time point. Quantitative polymerase chain reaction (qPCR) was used to measure Bifidobacteria and Lactobacillus CFUs at 24 h. WD produced the least gas during fermentation at 8, 12, and 24 h (P < 0.0001), while inulin produced the most by 8 h (P < 0.0001). Each fiber reached its lowest pH value at different time points with inulin at 8 h (mean ± SE) (5.94 ± 0.03), PHGG at 12 h (5.98 ± 0.01), and WD at 24 h (6.17 ± 0.03). All fibers had higher total SCFA concentrations compared to the negative control (P < 0.05) at 24 h. At 24 h, inulin produced significantly (P = 0.0016) more butyrate than WD with PHGG being similar to both. An exploratory microbial analysis (log(10) CFU/µL) showed WD had CFU for Bifidobacteria (6.12) and Lactobacillus (7.15) compared with the control (4.92 and 6.35, respectively). Rate of gas production is influenced by fiber source and may affect tolerance in vivo. Exploratory microbiota data hint at high levels of Bifidobacteria for WD, but require more robust investigation to corroborate these findings.