Prebiotic Effects and Fermentation Kinetics of Wheat Dextrin and Partially Hydrolyzed Guar Gum in an In Vitro Batch Fermentation System

Characteristics of exopolysaccharides from Paecilomyces hepiali and their simulated digestion and fermentation in vitro by human intestinal microbiota

The metabolic process of polysaccharides in gastrointestinal digestions and the effects of the resulting carbohydrates on the composition of gut microbes are important to explore their prebiotic properties. Therefore, the purpose of this study was to investigate the simulated digestion and fecal fermentation in vitro of three fractions (PHEPSs-1, PHEPSs-2 and PHEPSs-3) purified from the crude exopolysaccharides of Paecilomyces hepiali HN1 (PHEPSs) and to explore the potential prebiotic mechanisms. The three purified fractions were characterized by HPLC, UV, FT-IR, SEM and AFM, and they were all of galactoglucomannan family with molecular weight of 178, 232 and 119 kDa, respectively. They could resist the simulated gastrointestinal digestions, but they were metabolized in fecal fermentation in vitro. Furthermore, the mannose in PHEPSs showed a higher utilization rate than that of glucose or galactose. The proliferation effects of PHEPSs on Bifidobacterium and Lactobacillus were weaker significantly than those of fructooligosaccharides before 12 h of fecal fermentation, but stronger after 24 h of fecal fermentation. Meanwhile, higher levels of short-chain fatty acids were found in PHEPSs groups when the fecal fermentation extended to 36 h. Therefore, PHEPSs are expected to have a potent gut healthy activity and can be explored as functional food ingredients.

Looking inside Mexican Traditional Food as Sources of Synbiotics for Developing Novel Functional Products

Currently, emerging alimentary alternatives are growing, leading to the consumption of natural products including bio, fermented, and traditional foods. The studies over functional properties of food matrices and their derived compounds have resulted in the development of new functional alimentary items. However, most of the population still has limited access to, and information about, suitable foods. Analyzing traditional fermented products, we found fermented food matrices containing beneficial bacteria, with the possibility of exerting effects on different substrates enhancing the bioavailability of short-chain fatty acids (SFCAs), antioxidants, among other food-derived products. Maize (Zea mays L.), agave varieties, nopal (Opuntia ficus-indica), and beans (Phaseolus vulgaris L.) were key foods for the agricultural and nutritional development of Mesoamerica. We believe that the traditional Mexican diet has relevant ingredients with these functionalities and their association will allow us to develop functional food suitable for each population and their current needs. In this review, the functional properties of maize, agave, nopal, and frijol are detailed, and the functional food innovation and development opportunities for these food matrices are analyzed, which may be an important precedent for future basic and applied research.

Dietary fibre complexity and its influence on functional groups of the human gut microbiota

The aim of this review is to provide an overview of the complex interactions between dietary fibre and the resident microbial community in the human gut. The microbiota influences both health maintenance and disease development. In the large intestine, the microbiota plays a crucial role in the degradation of dietary carbohydrates that remain undigested in the upper gut (non-digestible carbohydrates or fibre). Dietary fibre contains a variety of different types of carbohydrates, and its breakdown is facilitated by many different microbial enzymes. Some microbes, termed generalists, are able to degrade a range of different carbohydrates, whereas others are more specialised. Furthermore, the physicochemical characteristics of dietary fibre, such as whether it enters the gut in soluble or insoluble form, also likely influence which microbes can degrade it. A complex nutritional network therefore exists comprising primary degraders able to attack complex fibre and cross feeders that benefit from fibre breakdown intermediates or fermentation products. This leads predominately to the generation of the short-chain fatty acids (SCFA) acetate, propionate and butyrate, which exert various effects on host physiology, including the supply of energy, influencing glucose and lipid metabolism and anti-carcinogenic and anti-inflammatory actions. In order to effectively modulate the gut microbiota through diet, there is a need to better understand the complex competitive and cooperative interactions between gut microbes in dietary fibre breakdown, as well as how gut environmental factors and the physicochemical state of fibre originating from different types of diets influence microbial metabolism and ecology in the gut.

Deciphering the colonic fermentation characteristics of agavin and digestion-resistant maltodextrin in a simulated batch fermentation system

Gut microbial fermentation of soluble dietary fibers promotes general and substrate-specific health benefits. In this study, the fermentation characteristics of two soluble branched-dietary fibers, namely, agavin (a type of agave fructans) and digestion-resistant maltodextrin (RD) were investigated against cellulose, using a simulated colonic fermenter apparatus employing a mixed culture of swine fecal bacteria. After 48 h of complete fermentation period, the microbial composition was different among all groups, where Bifidobacterium spp. and Lactobacillus spp. dominated the agavin treatment, while the members of the families Lachnospiraceae and Prevotellaceae dominated the RD treatment. Agavin treatment exhibited a clearly segregated two-phased prolonged fermentation trend compared to RD treatment as manifested by the fermentation rates. Further, the highest short-chain fatty acids production even at the end of the fermentation cycle, acidic pH, and the negligible concentration of ammonia accumulation demonstrated favorable fermentation attributes of agavin compared to RD. Therefore, agavin might be an effective and desirable substrate for the colonic microbiota than RD with reference to the expressed microbial taxa and fermentation attributes. This study revealed a notable significance of the structural differences of fermentable fibers on the subsequent fermentation characteristics.

Partially Hydrolyzed Guar Gum Modulates Gut Microbiota, Regulates the Levels of Neurotransmitters, and Prevents CUMS-Induced Depressive-Like Behavior in Mice

SCOPE

Depression is the leading cause of disability around the world; however, most antidepressants have drug tolerance and serious side effects. In this study, it is explored whether partially hydrolyzed guar gum (PHGG) is a safe food that exhibits protection in a mouse model of depression.

METHODS AND RESULTS

PHGG is orally administered to mice with depression induced by chronic unpredictable mild stress (CUMS) in two animal experiments (prevention trial and intervention trial) to characterize the potentially protective effect of PHGG. The results in the prevention trial show that PHGG significantly inhibits the loss of body weight, and prevents CUMS-induced depressive-like behavior in mice. The beneficial effects may be associated with PHGG modulating the gut microbiota structure and then increasing the levels of short-chain fatty acids in mice feces and the levels of 5-hydroxytryptamine and dopamine in serum, striatum, and hippocampus. Besides, PHGG in the intervention trial is less effective than that in the prevention trial, but it may have a synergistic effect on improving depression with fluoxetine.

CONCLUSIONS

This study suggests that moderate daily intake of PHGG can contribute to relieving depressive-like behavior.

Polylactose Exhibits Prebiotic Activity and Reduces Adiposity and Nonalcoholic Fatty Liver Disease in Rats Fed a High-Fat Diet

BACKGROUND

Prebiotic dietary fibers change the intestinal microbiome favorably and provide a health benefit to the host.

OBJECTIVES

Polylactose is a novel fiber, synthesized by extrusion of lactose. We evaluated its prebiotic activity by determining its fermentability, effect on the microbiota, and effects on adiposity and liver lipids in a diet-induced obesity animal model.

METHODS

Male Wistar rats (4-5 wk old) were fed normal-fat (NF, 25% fat energy) or high-fat (HF, 51% fat energy) diets containing different fibers (6% fiber of interest and 3% cellulose, by weight), including cellulose (NFC and HFC, negative and positive controls, respectively), polylactose (HFPL), lactose matched to residual lactose in the HFPL diet, and 2 established prebiotic fibers: polydextrose (HFPD) and fructooligosaccharide (HFFOS). After 10 wk of feeding, organs were harvested and cecal contents collected.

RESULTS

HFPL animals had greater cecum weight (3 times greater than HFC) and lower cecal pH (∼1 pH unit lower than HFC) than all other groups, suggesting that polylactose is more fermentable than other prebiotic fibers (HFPD, HFFOS; P < 0.05). HFPL animals also had increased taxonomic abundance of the probiotic species Bifidobacterium in the cecum relative to all other groups (P < 0.05). Epididymal fat pad weight was significantly decreased in the HFPL group (29% decrease compared with HFC) compared with all other HF groups (P < 0.05) and did not differ from the NFC group. Liver lipids and cholesterol were reduced in HFPL animals when compared with HFC animals (P < 0.05).

CONCLUSIONS

Polylactose is a fermentable fiber that elicits a beneficial change in the gut microbiota as well as reducing adiposity in rats fed HF diets. These effects of polylactose were greater than those of 2 established prebiotics, fructooligosaccharide and polydextrose, suggesting that polylactose is a potent prebiotic.

Perspective: Physiologic Importance of Short-Chain Fatty Acids from Nondigestible Carbohydrate Fermentation

In recent years, it has become increasingly obvious that dietary fiber or nondigestible carbohydrate (NDC) consumption is critical for maintaining optimal health and managing symptoms of metabolic disease. In accordance with this, the US FDA released its first official definition of dietary fiber in 2016 for regulation of Nutrition and Supplement Facts labels. Included in this definition is the requirement of an isolated or synthetic NDC to produce an accepted physiologic health benefit, such as improved laxation or reduced fasting cholesterol concentrations, upon consumption. Even though NDC fermentation and production of short-chain fatty acids elicit many physiologic effects, including serving as a source of energy for colonocytes, curbing glycemic response and satiety, promoting weight loss, enhancing mineral absorption, reducing systemic inflammation, and improving intestinal health, the process of fermentation is not considered a physiologic endpoint. Instead, expensive and laborious clinical trials must be conducted and an accepted physiologic benefit observed. In this review, we discuss the physiologic importance of NDC fermentation through extensive examination of clinical evidence and propose that the degree of fermentability of an NDC, rather than the endpoints of a clinical trial, may be appropriate for classifying it as a dietary fiber.

Hepatoprotective Potential of Partially Hydrolyzed Guar Gum against Acute Alcohol-Induced Liver Injury in Vitro and Vivo

Natural polysaccharides, particularly galactomannans, are potential candidates for treatment of alcoholic liver diseases (ALD). However, applications are restricted due to the physicochemical properties associated with the high molecular weight. In this work, guar gum galactomannans were partially hydrolyzed by β-mannanase, and the molecular mechanisms of hepatoprotective effects were elucidated both in vitro and in vivo. Release of lactate dehydrogenase and cytochrome C were attenuated by partially hydrolyzed guar gum (PHGG) in HepG2 cells, due to protected cell and mitochondrial membrane integrity. PHGG co-administration decreased serum amino transaminases and cholinesterase levels of acute alcohol intoxicated mice, while hepatic pathologic morphology was depleted. Activity of superoxide dismutase, catalase, and glutathione peroxidase was recovered to 198.2, 34.5, 236.0 U/mg protein, respectively, while malondialdehyde level was decreased by 76.3% (PHGG, 1000 mg/kg∙day). Co-administration of PHGG induced a 4.4-fold increment of p-AMPK expression, and lipid metabolism was mediated. PHGG alleviated toll-like-receptor-4-mediated inflammation via the signaling cascade of MyD88 and IκBα, decreasing cytokine production. Moreover, mediated expression of Bcl-2 and Bax was responsible for inhibited acute alcohol-induced apoptosis with suppressed cleavage of caspase 3 and PARP. Findings gained suggest that PHGG can be used as functional food supplement for the treatment of acute alcohol-induced liver injury.

Fiber Supplements Derived From Sugarcane Stem, Wheat Dextrin and Psyllium Husk Have Different In Vitro Effects on the Human Gut Microbiota

There is growing public interest in the use of fiber supplements as a way of increasing dietary fiber intake and potentially improving the gut microbiota composition and digestive health. However, currently there is limited research into the effects of commercially available fiber supplements on the gut microbiota. Here we used an in vitro human digestive and gut microbiota model system to investigate the effect of three commercial fiber products; NutriKane™, Benefiber® and Psyllium husk (Macro) on the adult gut microbiota. The 16S rRNA gene amplicon sequencing results showed dramatic fiber-dependent changes in the gut microbiota structure and composition. Specific bacterial OTUs within the families Bacteroidaceae, Porphyromonadaceae, Ruminococcaceae, Lachnospiraceae, and Bifidobacteriaceae showed an increase in the relative abundances in the presence of one or more fiber product(s), while Enterobacteriaceae and Pseudomonadaceae showed a reduction in the relative abundances upon addition of all fiber treatments compared to the no added fiber control. Fiber-specific increases in SCFA concentrations showed correlation with the relative abundance of potential SCFA-producing gut bacteria. The chemical composition, antioxidant potential and polyphenolic content profiles of each fiber product were determined and found to be highly variable. Observed product-specific variations could be linked to differences in the chemical composition of the fiber products. The general nature of the fiber-dependent impact was relatively consistent across the individuals, which may demonstrate the potential of the products to alter the gut microbiota in a similar, and predictable direction, despite variability in the starting composition of the individual gut microbiota.

Fermentability of Novel Type-4 Resistant Starches in In Vitro System

Resistant starches are non-digestible starches that are fermented in the colon by microbiota. These carbohydrates are prebiotic and can be beneficial to consumer health. Many types of resistant starch exist with varying physical properties that may result in differences in fermentability. The objective of this research project was to compare potential prebiotic effects and fermentability of four novel resistant starches using an in vitro fermentation system and measuring changes in total gas production, pH, and formation of SCFAs (short chain fatty acids). Fecal donations were collected from seven healthy volunteers. Four novel resistant starches, modified potato starch (MPS), modified tapioca starch (MTS), and modified maize starches (MMS-1 and MMS-2), were analyzed and compared to polydextrose and short chain fructooligosaccharides (FOS) as controls. After twenty-four hours of fermentation, MPS and MTS responded similarly in gas production (74 mL; 70.6 mL respectively), pH (5.93; 5.93 respectively), and SCFA production (Acetate: 115; 124, Propionate: 21; 26, Butyrate: 29; 31 μmol/mL respectively). While MMS-1 had similar gas production and individual SCFA production, the pH was significantly higher (6.06). The fermentation of MMS-2 produced the least amount of gas (22 mL), with a higher pH (6.34), and lower acetate production (78.4 μmol/mL). All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.

Low amounts of dietary fibre increase in vitro production of short-chain fatty acids without changing human colonic microbiota structure

This study investigated the effect of various prebiotics (indigestible dextrin, α-cyclodextrin, and dextran) on human colonic microbiota at a dosage corresponding to a daily intake of 6 g of prebiotics per person (0.2% of dietary intake). We used an in vitro human colonic microbiota model based on batch fermentation starting from a faecal inoculum. Bacterial 16S rRNA gene sequence analysis showed that addition of 0.2% prebiotics did not change the diversity and composition of colonic microbiota. This finding coincided with results from a clinical study showing that the microbiota composition of human faecal samples remained unchanged following administration of 6 g of prebiotics over seven days. However, compared to absence of prebiotics, their addition reduced the pH and increased the generation of acetate and propionate in the in vitro system. Thus, even at such relatively low amounts, prebiotics appear capable of activating the metabolism of colonic microbiota.

Prebiotic Dietary Fiber and Gut Health: Comparing the in Vitro Fermentations of Beta-Glucan, Inulin and Xylooligosaccharide

Prebiotic dietary fiber supplements are commonly consumed to help meet fiber recommendations and improve gastrointestinal health by stimulating beneficial bacteria and the production of short-chain fatty acids (SCFAs), molecules beneficial to host health. The objective of this research project was to compare potential prebiotic effects and fermentability of five commonly consumed fibers using an in vitro fermentation system measuring changes in fecal microbiota, total gas production and formation of common SCFAs. Fecal donations were collected from three healthy volunteers. Materials analyzed included: pure beta-glucan, Oatwell (commercially available oat-bran containing 22% oat β-glucan), xylooligosaccharides (XOS), WholeFiber (dried chicory root containing inulin, pectin, and hemi/celluloses), and pure inulin. Oatwell had the highest production of propionate at 12 h (4.76 μmol/mL) compared to inulin, WholeFiber and XOS samples (p < 0.03). Oatwell's effect was similar to those of the pure beta-glucan samples, both samples promoted the highest mean propionate production at 24 h. XOS resulted in a significant increase in the genus Bifidobacterium after 24 h of fermentation (0 h:0.67 OTUs (operational taxonomic unit); 24 h:5.22 OTUs; p = 0.038). Inulin and WholeFiber increased the beneficial genus Collinsella, consistent with findings in clinical studies. All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.

In vitro analysis of partially hydrolyzed guar gum fermentation differences between six individuals

Partially hydrolyzed guar gum (PHGG) is a fermentable, soluble, non-gelling fiber consumed as both a supplement and ingredient. PHGG supports bifidogenic and lactogenic growth, and increases the concentration of short chain fatty acids (SCFAs) in the distal intestine due to its fermentability. Changes in SCFA development due to the fermentation of dietary fibers in the colon have been widely studied, but there are limited studies analyzing the differences in SCFA development across multiple individuals (ages 23-68) exposed to the same dietary fiber (PHGG). With the six donors analyzed in this study, gas production varied from 59-80 mL/0.5 g fiber at 12 h and 85-93 mL/0.5 g fiber at 24 h between the six donors. At 12 h butyrate concentrations varied from 6.99 μmol mL(-1) to 23.84 μmol mL(-1) and from 8.78 μmol mL(-1) to 22.84 μmol mL(-1) at 24 h. Total SCFA concentration at 24 h ranged from 42.85 μmol mL(-1) to 91.17 μmol mL(-1). The overall average SCFA ratio for the six fecal donors was 30 : 45 : 25 (acetate : propionate : butyrate), which is similar to other fermentable fibers analyzed using in vitro systems. SCFA development in the distal intestine increases the amount of metabolizable energy from the diet, but varies greatly among people based primarily on the composition and changes of their gut microflora. With over a 2-fold difference in SCFA production, significant differences were found among healthy individuals fecal microflora when exposed to PHGG. Donor 6 SCFA concentrations decreased at 24 h, indicating a quicker fermentation process than the other five donors. All SCFAs measured fluctuated greatly among the six individuals within 24 h of analysis. Results of in vitro fermentation analyses are limited by the wide variation found with fecal donor.

Consumption of the Soluble Dietary Fibre Complex PolyGlycopleX(®) Reduces Glycaemia and Increases Satiety of a Standard Meal Postprandially

The effect of consumption of PolyGlycopleX^® (PGX^®) was compared to wheat dextrin (WD) in combination with a standard meal, on postprandial satiety and glycaemia in a double-blind, randomised crossover trial, of 14 healthy subjects trained as a satiety panel. At each of six two-hour satiety sessions, subjects consumed one of three different test meals on two separate occasions. The test meals were: a standard meal plus 5 g PGX; a standard meal plus 4.5 g of PGX as softgels; and a standard meal plus 5 g of WD. Subjects recorded fullness using a labelled magnitude scale at 0, 15, 30, 45, 60, 90, and 120 min and the total area under the curve (AUC), mean fullness vs. time was calculated. The meals with PGX (in granular and softgel form) gave higher satiety (AUC) (477 ± 121 and 454 ± 242 cm·min), than the meal with WD (215 ± 261 cm·min) (p < 0.001). Subjects had blood glucose levels measured after the meals with PGX (granules) and WD. Glucose response (AUC) was significantly lower (p < 0.001) after the PGX meal than for the WD meal.  The high viscosity reported for PGX is a likely mechanism behind the significant satiety and blood glucose modulating effects observed in this study.