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Dietary fiber is the undigested carbohydrate that escapes small intestinal digestion and absorption, and then reaches the large intestine for partial or complete fermentation by the colonic microbiota. Fermentation of dietary fiber into short-chain fatty acids (i.e., acetic, propionic, and butyric particularly) in the colon has been reported to bring about positive changes in microbiota composition and reduce the risk of colon-related diseases as well as some metabolic syndromes, such as obesity, diabetes, chronic kidney disease, and systemic inflammation. There is a growing interest in the fate of different dietary fibers in the gastrointestinal tract regarding their rate and extent (location) of fermentation and microbiota changes, particularly from data obtained with static and dynamic in vitro models. These models provide information on the fermentation performance and microbiota modulation by dietary fibers with diverse structures and enable the formulation of functional foods with health benefits. This review summarizes the fermentation performance of various dietary fibers using in vitro models. Both the physical and chemical structures of dietary fibers are critical factors that determine fermentation rate, short-chain fatty acid profiles and growth of different bacterial groups. Considering the potential relationship between fermentation performance and health, three principles for designing fermentable dietary fiber are proposed: slow fermentation in the colon; high butyrate and/or propionate production; and selective bacterial growth, promoting the beneficial bacteria that improve the intestinal barrier function. • Advantages and disadvantages of static and dynamic in vitro fecal fermentation models. • Summary of fermentation performance and microbiota modulation of various dietary fibers using in vitro models. • Three principles for designing fermentable dietary fiber are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Factors affecting the production of exopolysaccharide (EPS) from Enterobacter cloacae WD7 cultivated in basal medium (pH 7.0) using 1% w/v glucose as a carbon source for 5 days at 30°C were investigated. The EPS yield of 2.23gL−1 was obtained after 3 days cultivation. Among the carbon sources tested, 3% sucrose was selected and gave an EPS yield of 2.72gL−1. This indicated that sucrose is a better carbon source than the glucose used previously. The addition of either inorganic nitrogen [(NH4)2SO4, NH4Cl and NH4NO3] or organic nitrogen (polypeptone) sources had no effect on the EPS yield. The optimum concentration of yeast extract was found to be 0.05% w/v. The optimum environmental conditions were: initial pH 7.0, temperature 30°C, pH control at 7.0 and the aeration rate of 2.0vvm which elevated the EPS yield to 4.80gL−1 while further increase in the agitation speed (200rpm) reduced the production of EPS. Comparison of the kinetic parameters of the shake-flask and batch fermentations revealed that batch fermenter culture gave about 2 times higher values of specific growth rate (μ =0.15 and 0.29h−1), product yields (Y p/s =0.25 and 0.52g EPSgsucrose−1) and maximum productivity (R m =0.04 and 0.07g of EPSL−1 h−1). Substitution of the analytical grade sucrose by commercial sucrose resulted in 15% lower EPS yield (i.e. from 4.90 to 4.18gL−1, respectively) but could lower the raw material cost by 98%, and therefore is a suitable component for the production medium. For continuous culture studies, the optimum dilution rate was 0.05h−1 giving the maximum EPS concentration of 7.28gL−1 which is 1.5 times higher than the batch culture and a total of 3.2 times higher than the beginning (2.23gL−1). The critical dilution rate (D c) was calculated to be 0.49h−1 with the maximum dilution rate (D m) of 0.485h−1, Y x/s of 0.03gcell/gsucrose and the R m of 0.06g EPSL−1 h−1. Batch culture therefore gave a slightly higher productivity and would be the method of choice for scale-up studies. [Copyright &y& Elsevier]

[Display omitted] • Dietary polyphenols consumption influences the composition of gut microbiota. • Polyphenolic metabolites bio-transformed by the gut microbiota may contribute to the health benefits of the host. • Interplays among the polyphenols, microbiota and host were reviewed and summarised and future perspectives were provided. The beneficial health roles of dietary polyphenols in preventing oxidative stress related chronic diseases have been subjected to intense investigation over the last two decades. As our understanding of the role of gut microbiota advances our knowledge of the antioxidant and anti-inflammatory functions of polyphenols accumulates, there emerges a need to examine the prebiotic role of dietary polyphenols. This review focused on the role of different types and sources of dietary polyphenols on the modulation of the gut microbiota, their metabolites and how they impact on host health benefits. Inter-dependence between the gut microbiota and polyphenol metabolites and the vital balance between the two in maintaining the host gut homeostasis were discussed with reference to different types and sources of dietary polyphenols. Similarly, the mechanisms behind the health benefits by various polyphenolic metabolites bio-transformed by gut microbiota were also explained. However, further research should focus on the importance of human trials and profound links of polyphenols-gut microbiota-nerve-brain as they provide the key to unlock the mechanisms behind the observed benefits of dietary polyphenols found in vitro and in vivo studies. [ABSTRACT FROM AUTHOR]

• Gracilaria fisheri oligosaccharides (GFO) attenuated ulcerative colitis symptoms. • GFO improved gastrointestinal motility in acetic acid (AA)-induced colitis mice. • GFO restored colonic smooth muscle contractility in AA-induced colitis mice. • GFO modulated gut microbiota in AA-induced colitis mice. • GFO is suitable for inclusion as a food supplement to promote gut health. Oligosaccharides from red algae have demonstrated prebiotic activity. In this study, the prebiotic effects of Gracilaria fisheri oligosaccharides (GFO) on gastrointestinal (GI) motility in acetic acid (AA)-induced colitis mice were investigated through GI transit time, ex vivo propulsive motility, in vitro colonic smooth muscle contractility, composition of colonic microbiota, and production of short-chain fatty acids (SCFAs). Treatment with GFO attenuated histological change and shortening of the colon, reduced body weight loss, and lowered the disease activity index. Notably, GFO prevented reductions in gut transit, propulsive motility, and smooth muscle contractility in colitis mice. GFO treatment also modulated Enterobacteria populations and SCFAs production in the GI tract. The results suggested that the prebiotic effect of GFO could prevent and attenuate colitis symptoms and GI dysmotility in AA-induced colitis, perhaps by reducing populations of harmful bacteria and increasing SCFAs production. [ABSTRACT FROM AUTHOR]

• Soaking and germination significantly reduced starch digestion and glycemic index. • Phenolics, non-digestible carbohydrates promoted SCFAs, gut microbiota modulation. • Fermented soaked purple rice notably improved beneficial fecal bacteria. • Fecal fermented soaked sample exhibited 4 phenolic and 6 dietary fiber metabolites. This study revealed that soaking and germination significantly reduced (P < 0.05) the glycemic index of purple rice (72.64 ± 0.75–61.52 ± 3.11%) and lowest value was observed with 24 h soaked sample. Non-digestible starch and phenolic metabolites in soaked purple rice could be correlated with the increased amount of Bifidobacterium (log 9.62–10.21), Lactobacillus (log 8.55–9.30) and significant decrease (P < 0.05) in growth of Clostridium/Enterobacter and Bacteroides groups during fecal fermentation. Furthermore, highest concentrations of acetate (35.27 ± 0.09 mM) and prebiotic index (PI) score of 0.79 was recorded with the soaked sample after 48 h. Phenolic metabolites including pyrocatechol, 3-(4-hydroxyphenyl) propionic acid, salicylic acid, trans -cinnamic acid and non-digestible carbohydrates metabolites were identified by LC-MS. Therefore, the soaked purple rice could be a potential functional hypoglycemic ingredient for management of gut health, diabetes, obesity and gut-brain diseases such as memory improvement in elderly. [ABSTRACT FROM AUTHOR]

Abstract: Lactic acid bacteria (LAB) selected based on high EPSs production yields of 14, 7.6, 4.9 and 5g/L in sucrose containing MRS broth were identified as Weissella cibaria, Weissella confusa, Lactobacillus plantarum and Pediococcus pentosaceus, respectively based on their 16S rDNA sequences. EPSs produced by these strains did not stimulate secretion of interleukin (IL)-8, and were resistant to stomach acid and human pancreatic amylase. In pure culture system, only Bifidobacterium bifidum DSM 20456 exhibited the ability to utilize these EPSs as carbon sources but not L. plantarum TISTR 875 and Lactobacillus acidophilus TISTR 1034. EPSs from W. cibaria exhibited strong bifidogenic effect in the mixed-culture of human fecal microflora using the three-stage fermentation model. In the transverse and distal colon, bifidobacteria and lactobacilli as well as acetate and propionate increased significantly. Butyrate slightly decreased in the proximal colon region after feeding EPSs, but increased in the distal region. [Copyright &y& Elsevier]

[Display omitted] • The first clinical study confirmed the safety and efficacy of dragon fruit oligosaccharides (DFO) as an emerging prebiotic. • DFO improved the immune system (serum Ig A) at even a low dose (4 g/day). • DFO at 8 g/day outstandingly promoted the growth of Bifidobacterium spp. and decreased harmful bacteria, especially, Escherichia coli. • The potential dose of DFO for healthy adults was established as 4 g/day for improving IgA level and 8 g/day for promoting beneficial gut microbiota. Healthy food has wide popularity and relates positively to health. Our previous studies have shown that dragon fruit oligosaccharides (DFO) have prebiotic activities, balancing the gut microbiota in a simulated human colon system, and are safe and stimulate the immune system in rats. The effects of DFO on immune stimulation gut microbe modulation and the correlation of gut microbiota and nutrients were investigated in a human trial. This clinical study was a randomized, double-blinded, placebo-controlled trial. The participants were 107 healthy adults, divided into 3 groups that received DFO in drinking waterdoses of 4 and 8 g/day, compared to the placebo group for 4 consecutive weeks. DFO consumption at 4 g/day increased IgA level (11.31 mg/dL or 10.95% from baseline) and 8 g/day outstandingly promoted the growth of Bifidobacterium spp. (8.41%) and Faecalibacterium (1.99%) and decreased harmful bacteria, especially, Escherichia coli (8.44%). The relationship between gut microbes and nutrient intake was explored and significant (p < 0.05) correlations between specific microbial groups and intakes of specific macro- and micronutrients were observed. The potential dose of DFO for healthy adults was established as 4 g/day for improving IgA level and 8 g/day for promoting beneficial gut microbiota. [ABSTRACT FROM AUTHOR]

• Besides prebiotic-like effects, DFO acts as a bulk-forming and stimulant laxative. • DFO increased fecal pellet output and velocity. • DFO increased non-propagation contractions, eradicating diarrheal symptoms. • DFO increased colonic smooth muscle contractions without morphological effects. • DFO is suitable for inclusion as a food supplement to promote gut health. Dragon fruit oligosaccharide (DFO) has a prebiotic property which improves gut health by selectively stimulating the colonic microbiota. Altering microbiota composition may affect intestinal motility. However, no study has been done to understand the DFO effects on gut motor functions. This research thus aimed to investigate the DFO effects on mice colons compared to the prebiotic fructo-oligosaccharide (FOS) and probiotic bifidobacteria. The mice in this study received distilled water; 100, 500, and 1000 mg/kg DFO; 1000 mg/kg FOS; or 109 CFU Bifidobacterium animalis daily for 1 week and some treatments for 2 weeks. Gastrointestinal transits were analysed and motility patterns, smooth muscle (SM) contractions and morphological structures of the colons were assessed. Administration of FOS, 500 and 1000 mg/kg DFO significantly increased fecal output when compared to the control group. In mice treated with FOS and bifidobacteria, gut transit time was reduced, while upper gut transit was increased in comparison to DFO groups. Spatiotemporal maps of colonic wall motions showed that DFO increased the number of colonic non-propagation contractions and fecal pellet velocity, consistent with the results from groups treated with FOS and bifidobacteria. DFO also increased the amplitude and duration of colonic SM contractions. Histological stains showed normal epithelia, crypts, goblet cells, and SM thickness in all groups. In conclusion, DFO increased colonic SM contractions without morphological change and acted as a bulk-forming and stimulant laxative to increase fecal output and intestinal motility. Thus, DFO as a dietary supplement may promote gut health and correct gastrointestinal motility disorders. [ABSTRACT FROM AUTHOR]