Changes in dietary fiber fractions and gut microbial fermentation properties of wheat bran after extrusion and bread making

Study on the prebiotic effects of insoluble crude and fine fibers of wheat bran after simulated digestion in vitro

This study aims to evaluate the probiotic effects of insoluble crude and fine fibers of wheat bran on the intestine after simulated in vitro digestion. It was found that the particle size distribution of modified fine wheat bran (MWB) was significantly smaller than that of natural crude wheat bran (NWB). MWB had a looser texture and more porous structure. The dry matter digestibility and organic matter digestibility of MWB were 58.60 % and 59.05 %, which were significantly higher than that of NWB (53.64 % and 54.13 %). More SDF and free polyphenol were released from the MWB. At 12 h of fermentation, the SDF content of the MWB was 3.76 g/100 g, significantly higher than NWB (3.40 g/100 g), and the free polyphenol was 9.43 mg/g, significantly higher than NWB (9.01 mg/g). The content of short-chain fatty acids including formic acid, acetic acid, propionic acid, butyrate acid and valerate acid in the samples were significantly higher in MWB than in NWB. Analysis of the microbial flora structure and diversity of the fermentation samples revealed that the relative abundance of Lactobacillus was higher in the MWB group, and was closer to the oligofructose group (FOS) in terms of functional predictions.

The Influence of Processing Using Conventional and Hybrid Methods on the Composition, Polysaccharide Profiles and Selected Properties of Wheat Flour Enriched with Baking Enzymes

In this study, a developed wheat flour blend (F), consisting of a high content of non-starch polysaccharides, was fortified with cellulase (C) and a cellulase-xylanase complex (CX) and then processed via conventional and hybrid treatment methods. Dry heating (T), hydrothermal treatment (H) and extrusion processing (E) were applied without or with enzyme addition as hybrid treatments. Proximate composition and polysaccharide profiles selected techno-functional and structural properties of modified wheat flours, were analyzed. Conventional and hybrid treatments induced changes in polysaccharide fraction compositions (especially the arabinoxylans) and the rheology of modified flour. Dry heating caused an inconsiderable effect on flour composition but reduced its baking value, mainly by reducing the elasticity of the dough and worsening the strain hardening index, from 49.27% (F) to 44.83% (TF) and from 1.66 (F) to 1.48 (TF), respectively. The enzymes added improved the rheological properties and baking strength, enhancing the quality of gluten proteins. Hydrothermal enzyme-assisted treatment increased flour viscosity by 14-26% and improved the dough stability by 12-21%; however, the use of steam negatively affected the protein structure, weakening dough stretchiness and elasticity. Extrusion, especially enzyme-assisted, significantly increased the hydration properties by 55-67% but lowered dough stability, fat content and initial gelatinization temperature due to the changes in the starch, mostly induced by the hybrid enzymatic-extrusion treatment. The structure of extruded flours was different from that obtained for other treatments where the peak intensity at 20° was the highest, suggesting the presence of amorphous phases of amylose and lipids. The results can be helpful in the selection of processing conditions so as to obtain flour products with specific techno-functional properties.

Impact of whole grain highland hull-less barley on the denaturing gradient gel electrophoresis profiles of gut microbial communities in rats fed high-fat diets

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) is a traditional non-culture technique that can provide a fingerprint of the microbial community. In the field of gut microbiota analysis, PCR-DGGE still holds potential for development. In the present study, we utilized an improved nested PCR-DGGE approach targeting the V3 region of 16S ribosomal DNA to investigate the impact of whole grain highland hull-less barley (WHLB), a cereal known for its significant hypocholesterolemic effect, on the gut microbiota profiles of high-fat diet rats. Seventy-two male Sprague-Dawley rats were divided into four groups and fed a normal control diet, a high-fat diet, or a high-fat diet supplemented with a low or high dose of WHLB for 4 or 8 weeks. The results revealed that the dominant bands varied among different dose groups and further changed with different treatment times. The compositions of bacterial communities in feces and cecal content were similar, but the dominant bacterial bands differed. After performing double DGGE, extracting the bands, sequencing the DNA, and aligning the sequences, a total of 19 bands were classified under the Firmicutes and Bacteroidetes phyla, while two bands were identified as unclassified uncultured bacteria. The relative abundance of Lactobacillus gasseri, Uncultured Prevotella sp., and Clostridium sp. increased following the administration of WHLB. Illumina-based sequencing was employed to assess the reliability of DGGE, demonstrating its reliability in analyzing the dominant taxonomic composition, although it may have limitations in accurately detecting the alpha diversity of bacterial species.

IMPORTANCE

While next-generation sequencing has overshadowed polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), the latter still holds promise for advancing gut microbiota analysis due to its unique advantages. In this study, we used optimized nested PCR-DGGE to investigate the gut microbiota profile of high-fat diet rats after administering whole grain highland hull-less barley. High-throughput sequencing was employed to validate the DGGE results. Our results proved the reliability of PCR-DGGE for analyzing the dominant taxonomic composition while also providing visual evidence of a notable relationship between the composition of cecal and fecal microbial communities, highlighting substantial differences in both richness and abundance.

Jatobá-do-cerrado (Hymenaea stigonocarpa Mart.) pulp positively affects plasma and hepatic lipids and increases short-chain fatty acid production in hamsters fed a hypercholesterolemic diet

This study aimed to assess the impact of jatobá pulp, in its fresh (FJ) and extruded (EJ) forms, on lipid metabolism and intestinal fermentation parameters in hamsters. In a 21-day experiment, we determined the parameters of the animal lipid metabolism and colonic production of short chain fatty acids in four different groups. Control (C), fresh pulp (FJ) and extruded pulp (EJ) were fed using hypercholesterolemic diets, and the reference (R) was fed using AIN93 meal. R and C diets contained cellulose, FJ and EJ were added by jatobá pulp as a fiber source. The results showed that FJ and EJ exhibited lower levels of triglycerides, total cholesterol, LDL-c, non-HDL-c serum levels, liver lipids, and liver weight compared to C. The EJ had higher bile acid excretion in stool than the C. EJ and FJ exhibited lower excreted fiber compared to R and C, implying greater fermentation. Furthermore, the production of short-chain fatty acids (SCFA) in the cecum of FJ and EJ animals exceeded that of the C. Acetic and propionic acids were more abundant in the FJ and EJ diets, with FJ producing more butyric acid than the other groups.In conclusion, jatobá pulp maintained at normal levels of total cholesterol, LDL and HDL-associated cholesterol, non-HDL cholesterol, and serum triglycerides, while also reducing the accumulation of hepatic lipids. Jatobá also promoted SCFA formation and fermentation, making it a valuable ingredient for preventing chronic diseases.

Extrusion Modification of Wheat Bran and Its Effects on Structural and Rheological Properties of Wheat Flour Dough

The study investigated the extrusion modification of wheat bran and its effects on structural and rheological properties of wheat flour dough. Extruded bran showed better solubility of dietary fiber and structural porosity, leading to higher hydration and swelling power. Addition of extruded bran to dough caused water redistribution as an intensive aggregation of bound water to gluten matrix with reduced mobility. The bran-gluten interaction influenced by water sequestering caused partial gluten dehydration and conversion of β-turn into β-sheet, which demonstrated the formation of a more polymerized and stable gluten network. Farinographic data confirmed the promotion of dough stability with extruded bran addition at lower gluten content, while viscoelastic data suggested improved dough elasticity at all gluten contents by increasing elastic moduli and decreasing loss tangent. This study would be useful for interpreting the modification effect and mechanism of extrusion on cereal brans and provide valuable guidance for applying it as an effective modification technology on the commercial production of cereal bran and its flour products.

Effect of physicochemical properties, pre-processing, and extraction on the functionality of wheat bran arabinoxylans in breadmaking - A review

Arabinoxylan (AX) is an abundant hemicellulose in wheat bran and an important functional component in bakery products. This review compares preprocessing and extraction methods, and evaluates their effect on AX properties and functionality as a bread ingredient. The extraction process results in AX isolates or concentrates with varying molecular characteristics, indicating that the process can be adjusted to produce AX with targeted functionality. AX functionality in bread seems to depend on AX properties but also on AX addition level and interactions with other components. This review suggests that the use of AX with tailored properties together with properly optimized baking process could help increasing the amount of added fiber in bread while maintaining or even improving bread quality.

Dietary fiber in bakery products: Source, processing, and function

Bakery products are prevalently consumed foods in the world, and they have been regarded as convenient dietary vehicles for delivering nutritive ingredients into people's diet, of which, dietary fiber (DF) is one of the most popular items. The food industry attempts to produce fiber-enriched bakery products with both increasing nutritional value and appealing palatability. As many new sources of DFs become available, and consumers are moving towards healthier diets, studies of using these DFs as functional ingredients in baked goods are becoming vast. Besides, the nutrition value of DF is commonly accepted, and many investigations have also revealed the health benefits of fiber-enriched bakery products. Thus, this chapter presents an overview of (1) trends in supplementation of DF from various sources, (2) impact of DF on dough processing, quality and physiological functionality of bakery products, and (3) technologies used to improve the compatibility of DF in bakery products.

Processing Agroindustry By-Products for Obtaining Value-Added Products and Reducing Environmental Impact

Over four billion tons of foods are produced annually on the planet, and about a third is wasted. A minimal part of this waste is incinerated or sent to landfills for treatment, avoiding contamination and diseases; the rest is disposed of elsewhere. The current review was aimed at broadening the panorama on the potential of agroindustrial by-products in applications such as biofuels, biomaterials, biocompounds, pharmaceuticals, and food ingredients. It also exposes the main chemical, physical, and biochemical treatments for converting by-products into raw materials with added value through low environmental impact processes. The value of agroindustrial waste is limited due to the scarce information available. There is a need for further research in unexplored areas to find ways of adding value to these by-products and minimizing their contamination. Instead of throwing away or burning by-products, they can be transformed into useful materials such as polymers, fuels, antioxidants, phenols, and lipids, which will effectively reduce food waste and environmental impact.

Extrusion Cooking Effect on Carbohydrate Fraction in Novel Gluten-Free Flours Based on Chickpea and Rice

Extrusion cooking allows the development of value-added products from pulses, such as gluten-free snacks with added functional properties. The main objective of this study was to evaluate the changes induced by the extrusion process on the carbohydrate fraction (total carbohydrates, soluble sugars and oligosaccharides, dietary fiber, and arabinoxylans) of novel flour formulations based on chickpeas and rice enriched with different dietary fiber sources. Moreover, the influence of the addition of fiber-rich ingredients, such as Fibersol^® and passion fruit, on the analyzed compounds was also evaluated. Sucrose was the main soluble sugar found in analyzed formulations, and raffinose was the prevalent oligosaccharide, followed by stachyose. The content of total α-galactosides tended to be higher after extrusion cooking. As a consequence of the extrusion treatment, the content of total and soluble dietary fiber was statistically increased in most of the analyzed samples. In general, no significant changes were observed in total arabinoxylan content as a consequence of the extrusion process, while the content of water-soluble arabinoxylans was significantly increased in extruded formulations. It was observed that the content of total available carbohydrates, stachyose, and water-soluble arabinoxylans were significantly influenced by the addition of passion fruit, Fibersol^®, and both. The incorporation of these ingredients in gluten-free formulations based on chickpeas and rice allows one to obtain suitable functional formulations for the development of innovative, gluten-free, extruded snack-type products, which could be an interesting alternative for people with celiac disease.

The influence of food processing methods on serum parameters, apparent total-tract macronutrient digestibility, fecal microbiota and SCFA content in adult beagles

Food processing methods may influence the health of dogs. However, previous studies have mostly been based on a comparison of several commercial dog foods with different ingredients. In this study, eighteen adult beagles of the same age and health status (assessed by routine blood tests) were used in the experiments. This study analyzed the effects of the following different processing methods: raw, pasteurized, and high temperature sterilization (HTS) made with the same ingredients and nutrients (based on dry matter) on serum parameters, apparent total-tract macronutrient digestibility, fecal microbiota and short-chain fatty acid (SCFA) content in beagle dogs. The data showed, after a test lasting 56-days, the apparent digestibility (ATTD) of protein and fat in HTS food was 91.9%, which was significantly higher (P< 0.05) than that in dry food (89.2%, P < 0.05). The serum content of triglyceride increased in beagles fed HTS food (P < 0.05), and the number of neutrophils in beagles fed raw food and pasteurized food increased significantly (P < 0.05), and the platelet count in beagles fed raw food showed an increasing trend compared with the beagles fed HTS food. Different processing methods had an impact on the intestinal microbiota and SCFA of beagles; at least 14 genera were significantly affected by the food produced using different processing methods. In particular, the abundance of Allprevotella, Escherichia-Shigella and Turicibacter, and the total acid content were lower in beagles fed the raw diet, whereas Streptococcus, Collinsella, Bacteroides and Ruminococcus gnavus were more abundant following the HTS diet, and Lactococcus showed the highest abundance in beagles fed the pasteurized diet. This study showed that dog food produced by different processing methods affected the health of adult beagles.

Carbohydrate utilization by the gut microbiome determines host health responsiveness to whole grain type and processing methods

Little is known about how interactions among grain processing, grain type, and carbohydrate utilization (CU) by the microbiome influence the health benefits of whole grains. Therefore, two whole grains - brown rice and whole wheat - and two processing methods - boiling (porridge) and extrusion - were studied for their effects on host metabolic outcomes in mice harboring human microbiomes previously shown in vitro to have high or low CU. Mice carrying either microbiome experienced increases in body weight and glycemia when consuming Western diets supplemented with extruded grains versus porridge. However, mice with the high but not low CU microbiome also gained more weight and fat over time and were less glucose tolerant when consuming extruded grain diets. In high CU microbiome mice, the exacerbated negative health outcomes associated with extrusion were related to altered abundances of Lachnospiraceae and Ruminococcaceae as well as elevated sugar degradation and colonic acetate production. The amplicon sequence variants (ASVs) associated with extruded and porridge diets in this in vivo study were not the same as those identified in our prior in vitro study; however, the predicted functions were highly correlated. In conclusion, mice harboring both high and low CU microbiomes responded to the whole grain diets similarly, except the high CU microbiome mice exhibited exacerbated effects due to excessive acetate production, indicating that CU by the microbiome is linked to host metabolic health outcomes. Our work demonstrates that a greater understanding of food processing effects on the microbiome is necessary for developing foods that promote rather than diminish host health.Abbreviations: CU- carbohydrate utilization; SCFA- short-chain fatty acids; GF- germ-free; HMA, human-microbiome associated; ipGTT- intraperitoneal glucose tolerance test; HOMA-IR- Homeostatic Model Assessment for Insulin Resistance; AUC- area under the glycemia curve; ASV- amplicon sequence variant; lf- low-fat; wd- Western diet; wd_wwp- Western diet containing whole wheat porridge; wd_wwe- Western diet containing whole wheat extrudate; wd_bre- Western diet containing brown rice extrudate; wd_extr- Western diet containing either whole wheat or brown rice extrudate.

Chlorogenic acid inhibits trimethylamine-N-oxide formation and remodels intestinal microbiota to alleviate liver dysfunction in high L-carnitine feeding mice

High L-carnitine ingestion has been shown to cause liver injury, mechanically due to an elevated circulating level of trimethylamine-N-oxide (TMAO), a gut microbiota-derived metabolite from L-carnitine. This study aimed to investigate whether chlorogenic acid (CGA), a health-promoting polyphenol, could inhibit TMAO formation and thereafter might prevent L-carnitine-induced liver injury in mice. Feeding of mice with 3% L-carnitine in drinking water increased the serum and urinary levels of TMAO (p < 0.01 vs. Normal), whereas the serum and urinary TMAO formation was sharply reduced by CGA administration (p < 0.01). At the phylum level, CGA inhibited the L-carnitine-induced increase in the abundance of Firmicutes and Proteobacteria, while it promoted Bacteroidetes. At the genus level, CGA notably increased the abundance of Akkermansia and Bacteroides, but reduced the population of Erysipelatoclostridium, Faecalibaculum and Erysipelotrichaceae in high L-carnitine feeding mice. Meanwhile, CGA caused strong inhibition against the increase of liver injury markers (i.e. AST, ALT and ALP), hepatic inflammatory cytokines (i.e. IL-1, IL-6, TNF-α and TNF-β) and dyslipidemia (i.e. TC, TG, LDL-C and HDL-C) in L-carnitine-fed mice (p < 0.05). These findings suggest that CGA holds great potential to alleviate liver dysfunction induced by high L-carnitine ingestion. The beneficial effect might be attributed to the protection against TMAO formation and the improvement of the health-promoting gut microbiota, as well as the antioxidant and anti-inflammatory properties of CGA.

Wheat Bran Modifications for Enhanced Nutrition and Functionality in Selected Food Products

The established use of wheat bran (WB) as a food ingredient is related to the nutritional components locked in its dietary fibre. Concurrently, the technological impairment it poses has impeded its use in product formulations. For over two decades, several modifications have been investigated to combat this problem. Ninety-three (93) studies (review and original research) published in English between January 1997 and April 2021 reporting WB modifications for improved nutritional, structural, and functional properties and prospective utilisation in food formulations were included in this paper. The modification methods include mechanical (milling), bioprocessing (enzymatic hydrolysis and fermentation with yeasts and bacteria), and thermal (dry heat, extrusion, autoclaving), treatments. This review condenses the current knowledge on the single and combined impact of various WB pre-treatments on its antioxidant profile, fibre solubilisation, hydration properties, microstructure, chemical properties, and technological properties. The use of modified WB in gluten-free, baked, and other food products was reviewed and possible gaps for future research are proposed. The application of modified WB will have broader application prospects in food formulations.

Effect of Using Quinoa Flour (Chenopodium quinoa Willd.) on the Physicochemical Characteristics of an Extruded Pasta

Quinoa is a promising raw material for the production of foods with high nutritional quality. This study used quinoa flour (Chenopodium quinoa Willd.), egg white, and yucca starch to obtain an extruded pasta. By means of a proximate analysis, the nutritional content of the raw materials, uncooked and cooked pasta, was evaluated. The effects of quinoa flour on the protein composition, physical properties (color, texture, loss through cooking, water absorption, and swelling indices), moisture, DSC, and SEM were evaluated through its comparison with a commercial pasta (control) formulated with quinoa (PCQ). The values obtained during the study were subjected to a simple analysis of variance (ANOVA) to determine the interaction between the factors and the variables by using a statistical program. Incorporation of quinoa flour in the formulations (F1, F2, and F3) increased notoriously the protein content (p < 0.05) and decreased the carbohydrate content, and no significant differences were observed for lipids and ash. The energy value increased due to the essential amino acids present in quinoa. The values obtained for L∗, a∗, and b∗ increased with the increase in quinoa flour, and significant differences for b∗ (p < 0.05) were attributed to the characteristic color of quinoa, drying time, and moisture content. The lack of molecular interaction between starch and protein due to the conditions used in the extrusion process influenced the decrease in rupture strength, increase in the water absorption and swelling indices, and losses due to cooking (8 g/100 g) within an acceptable range. Consequently, affected by the enthalpy of fusion, the starch granules of the quinoa flour did not gelatinize, as observed in the SEM micrographs. The results obtained and the parameters used in the extrusion process influenced the characteristics of the pasta, indicating that quinoa flour is a promising raw material for obtaining gluten-free products.

Processing Has Differential Effects on Microbiota-Accessible Carbohydrates in Whole Grains during In Vitro Fermentation

Whole grains are generally low in nondigestible carbohydrates that are available for fermentation by the gut microbiota, or microbiota-accessible carbohydrates (MAC). However, there is potential to increase MAC in whole grains through food processing. Five processing methods: boiling, extrusion, sourdough bread, unleavened bread, and yeast bread, were applied to whole wheat flour and then subjected to in vitro digestion followed by fermentation using fecal microbiomes from 10 subjects. The microbiomes separated into 2 groups: those that showed high carbohydrate utilization (CU) and those that exhibited low CU. The former exhibited not only enhanced CU but also increased butyrate production (MAC, 31.1 ± 1.1% versus 19.3 ± 1.2%, P < 0.001; butyrate, 5.26 ± 0.26 mM versus 3.17 ± 0.27 mM, P < 0.001). Only the microbiomes in the high-CU group showed significant differences among processing methods: extrusion and sourdough bread led to dichotomous results for MAC and short-chain fatty acid production, where extrusion resulted in high MAC but low butyrate production while sourdough bread resulted in low MAC but high butyrate production. Extrusion led to a noticeable decrease in α-diversity and some members of the families Ruminococcaceae and Lachnospiraceae, with increases in Acinetobacter, Enterococcus, and Staphylococcaceae This study demonstrated that only microbiomes that exhibited high CU responded to the effects of processing by showing significant differences among processing methods. In these microbiomes, extrusion was able to increase accessibility of the cell wall polysaccharides but did not increase butyrate production. In contrast, sourdough bread led to high butyrate production by supporting important butyrate-producers in the families Lachnospiraceae and Ruminococcaceae IMPORTANCE Dietary nondigestible carbohydrates, or dietary fiber, have long been recognized for their beneficial health effects. However, recent studies have revealed that fermentation of nondigestible carbohydrates by gut bacteria is critical in mediating many of the health-promoting properties of dietary fibers. Whole grains are excellent candidates to supply the microbiome with a plentiful source of nondigestible carbohydrates, although unfortunately a majority of these carbohydrates in whole grains are not available to gut bacteria for fermentation. Processing is known to alter the structural characteristics of nondigestible carbohydrates in whole grains, yet the relationship between these effects and gut microbial fermentation is unknown. This research aimed to address this important research gap by identifying interactions between whole-grain processing and gut bacteria, with the ultimate goal of increasing the availability of nondigestible carbohydrates for fermentation to enhance host health.

Anti-inflammatory activity of a water-soluble polysaccharide from the roots of purple sweet potato

In this study, a water-soluble polysaccharide was isolated from purple sweet potato roots. The in vitro and in vivo anti-inflammatory effects of the polysaccharide were evaluated by lipopolysaccharide (LPS)-induced inflammatory RAW264.7 macrophages and mice, respectively. The in vitro anti-inflammatory assay showed that the polysaccharide could effectively inhibit the overproduction of nitric oxide and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) while increasing the secretion of anti-inflammatory cytokine (IL-10). The in vivo anti-inflammatory assay revealed that mice administered with the polysaccharide showed higher IL-10, SOD, and T-AOC levels but lower TNF-α, IL-1β, IL-6 and MDA levels as compared to the LPS-treated model. Meanwhile, mice administered with the polysaccharide showed increased abundance of Lachnospiraceae, Lactobacillales and Parabacteroides but decreased amounts of Psychrobacter and Staphylococcus as compared to the LPS model group. Moreover, mice administered with polysaccharide showed enhanced production of short chain fatty acids by gut microbiota in the lipopolysaccharide-induced inflammatory mice. Our results suggested that the water-soluble polysaccharide from purple sweet potato roots could be utilized as a novel anti-inflammatory agent.

A water-soluble polysaccharide from purple sweet potato roots played anti-inflammatory roles by regulating inflammatory cytokines, gut microbiota and antioxidant defense system.

Decaisnea insignis Seed Oil Inhibits Trimethylamine-N-oxide Formation and Remodels Intestinal Microbiota to Alleviate Liver Dysfunction in l-Carnitine Feeding Mice

Elevated circulating level of the intestinal microbiota-derived l-carnitine metabolite trimethylamine-N-oxide (TMAO) has recently been linked to many chronic diseases. The purpose of our study was to investigate the effects of omega-7-enriched Decaisnea insignis seed oil (DISO) on reducing TMAO formation to prevent the l-carnitine-induced hepatic damage in mice. Feeding of mice with 3% l-carnitine in drinking water clearly increased the serum and urinary levels of TMAO (p < 0.05 vs Normal), whereas the serum and urinary TMAO formation was sharply reduced by DISO administration (p < 0.05). Meanwhile, DISO resulted in strong inhibition against the elevation of hepatic injury marker (AST, ALT, and ALP) activities and dyslipidemia (TC, TG, LDL-C, and HDL-C), as well as liver inflammatory cytokine (IL-1, IL-6, TNF-α, and TNF-β) release in l-carnitine-fed mice (p < 0.05). As revealed by 16S rDNA gene sequencing, DISO significantly inhibited the l-carnitine-induced elevations in the abundance of Firmicutes, Proteobacteria, and Erysipelotrichaceae and the increases in the proportion of Lactobacillus and Akkermansia, revealing that DISO attenuated the l-carnitine-caused gut dysbiosis. These findings suggested that DISO could alleviate liver dysfunction in l-carnitine-fed mice, which might be due to the protection against TMAO formation by modulating the gut microbiota.

Effects of Dietary Fiber Supplementation on Fatty Acid Metabolism and Intestinal Microbiota Diversity in C57BL/6J Mice Fed with a High-Fat Diet

This work was to assess possible impacts of novel insoluble fiber 8% bacterial cellulose (BC), soluble fiber 8% konjac glucomannan (KGM), and their mixture (4% BC/4% KGM) on fatty acid metabolism and intestinal microbiota of C57BL/6J mice fed with a high-fat diet (HFD). HFD-fed mice receiving the dietary fibers (DFs) for 16 weeks exhibited an improvement in lipid-associated cytokines and a decrease in inflammation factors, which was associated with the improved hepatic and serum fatty acid composition. The DFs, notably the mixed BC/KGM, elevated the HFD-caused decrease in the contents of acetic acid (from 23.9 ± 0.85 to 32.2 ± 0.84 mM/g; p < 0.05), propionic acid (from 6.53 ± 0.28 to 12.8 ± 0.58 mM/g; p < 0.05), and butyric acid (from 7.73 ± 0.43 to 13.5 ± 0.47 mM/g; p < 0.05). Furthermore, the mixed BC/KGM significantly decreased the abundance of Firmicutes (from 90.4 to 67.6%) and Mucispirillum (from 4.77 to 1.58%) and dramatically increased the abundance of Bacteroidetes (from 7.83 to 25.0%) and Akkermansia (from 0.69 to 2.80%) in the gut of HFD-fed mice at the genus level. Moreover, correlation analysis revealed that the multiplicity of gut microbiota was useful in sustaining colonic integrity through producing short-chain fatty acids to some extent. This finding suggests that a mixture of insoluble BC and soluble KGM has positive effects on modulation of the intestinal microecosystem in mice.

Complementary effects of cereal and pulse polyphenols and dietary fiber on chronic inflammation and gut health

Cereal grains and grain pulses are primary staples often consumed together, and contribute a major portion of daily human calorie and protein intake globally. Protective effects of consuming whole grain cereals and grain pulses against various inflammation-related chronic diseases are well documented. However, potential benefits of combined intake of whole cereals and pulses beyond their complementary amino acid nutrition is rarely considered in literature. There is ample evidence that key bioactive components of whole grain cereals and pulses are structurally different and thus may be optimized to provide synergistic/complementary health benefits. Among the most important whole grain bioactive components are polyphenols and dietary fiber, not only because of their demonstrated biological function, but also their major impact on consumer choice of whole grain/pulse products. This review highlights the distinct structural differences between key cereal grain and pulse polyphenols and non-starch polysaccharides (dietary fiber), and the evidence on specific synergistic/complementary benefits of combining the bioactive components from the two commodities. Interactive effects of the polyphenols and fiber on gut microbiota and associated benefits to colon health, and against systemic inflammation, are discussed. Processing technologies that can be used to further enhance the interactive benefits of combined cereal-pulse bioactive compounds are highlighted.

Artificial simulation of salivary and gastrointestinal digestion, and fermentation by human fecal microbiota, of polysaccharides from Dendrobium aphyllum

In vitro salivary and gastrointestinal (GI) digestion and fermentation of polysaccharides extracted from Dendrobium aphyllum were investigated in this study. Salivary amylase showed no influence on D. aphyllum polysaccharides (DAP). The molecular weight of DAP decreased dramatically during the first 0.5 h of gastric digestion, and then reduced steadily during the subsequent GI tract consumption. The content of reducing sugars increased steadily during GI digestion. Only released free mannose of DAP was detectable by gas chromatography-mass spectrometry analysis during the first 12 h of fermentation, which was contributed by fecal microbiota metabolism. In terms of the fermentation pattern, the pH dropped significantly due to the formation of six types of short-chain fatty acids (SCFAs). This study demonstrates that polysaccharides extracted from D. aphyllum can be digested by the GI tract and are physiologically active in the human large bowel by lowering the pH of the large intestinal environment and promoting the production of SCFAs.

D. aphyllum polysaccharide showed variational tendencies after artificial stimulated gastrointestinal digestion and fermentation by human feces.

Whole cereal grains and potential health effects: Involvement of the gut microbiota

The intakes of whole cereal grains (WCGs) have long been linked to decreased risks of metabolic syndromes (MetS) and several chronic diseases. Owing to the complex range of components of cereals, which may show synergistic activities to mediate these protective effects, the mechanisms by which the benefits of whole cereals arise are not fully understood. The gut microbiota has recently become a new focus of research at the intersection of diet and metabolic health. Moreover, cereals contain various ingredients known as microbiota-accessible substrates that resist digestion in the upper gastrointestinal tract, including resistant starch and non-starch polysaccharides such as β-glucan and arabinoxylans, making them an important fuel for the microbiota. Thus, WCGs may manipulate the ecophysiology of gut microbiota. In this review, the scientific evidence supporting the hypothesis that WCGs prevent MetS by modulating gut microbiota composition and functions are discussed, with focuses on cereal intake-related mechanisms by which gut microbiota contributes to human health and scientific evidences for the effects of WCGs on modulating gut microbiota. Once strong support for the association among WCGs, gut microbiota and host metabolic health can be demonstrated, particular cereals, their processing technologies, or cereal-based foods might be better utilized to prevent and possibly even treat metabolic disease.

Polysaccharide from wheat bran induces cytokine expression via the toll-like receptor 4-mediated p38 MAPK signaling pathway and prevents cyclophosphamide-induced immunosuppression in mice

Wheat bran-derived polysaccharides have attracted particular attention due to their immunomodulatory effects. However, the molecular mechanisms underlying their functions are poorly understood. The current study was designed to examine the effect of wheat bran polysaccharide (WBP) on RAW 264.7 cells and the underlying signaling pathways, which have not been explored. In addition, we also investigated the immuno-enhancement effects of WBP on cyclophosphamide (CTX)-induced immunosuppression in mice. WBP significantly increased the concentrations of intracellular nitric oxide (NO) and cytokines such as prostaglandin E₂ (PGE₂) and tumor necrosis factor-α (TNF-α) in RAW 264.7 cells. The result of RT-PCR analysis indicated that WBP also enhanced inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α expression. Further analyses demonstrated that WBP rapidly activated phosphorylated p38 mitogen-activated protein kinase (MAPK) and the transcriptional activities of activator protein-1 (AP-1) and nuclear factor (NF)-κB via toll-like receptor 4 (TLR4). Furthermore, in vivo experiments revealed that WBP increased the spleen and thymus indices significantly, and markedly promoted the production of the serum cytokines IL-2 and IFN-γ in CTX-induced immunosuppressed mice. Taken together, these results suggest that WBP can improve immunity by enhancing immune function, and could be explored as a potential immunomodulatory agent in functional food.

Enzymatic Modification of Corn Starch Influences Human Fecal Fermentation Profiles

Enzymatically modified starches have been widely used in food applications to develop new products, but information regarding digestion and fecal fermentation of these products is sparse. The objective of this study was to determine the fermentation properties of corn starch modified with α-amylase, amyloglucosidase, or cyclodextrin glycosyltransferase and the possible role of hydrolysis products. Samples differed in their digestibility and availability to be fermented by the microbiota, resulting in differences in microbial metabolites produced during in vitro fermentation. The presence or absence of hydrolysis products and gelatinization affected starch composition and subsequent metabolite production by the microbiota. Amyloglucosidase-treated starch led to the greatest production of short- and branched-chain fatty acid production by the microbiota. Results from this study could be taken into consideration to confirm the possible nutritional claims and potential health benefits of these starches as raw ingredients for food development.

Moisture content during extrusion of oats impacts the initial fermentation metabolites and probiotic bacteria during extended fermentation by human fecal microbiota

Extrusion exposes flour components to high pressure and shear during processing, which may affect the dietary fiber fermentability by human fecal microbiota. The objective of this study was to determine the effect of flour moisture content during extrusion on in vitro fermentation properties of whole grain oats. Extrudates were processed at three moisture levels (15%, 18%, and 21%) at fixed screw speed (300rpm) and temperature (130°C). The extrudates were then subjected to in vitro digestion and fermentation. Extrusion moisture significantly affected water-extractable β-glucan (WE-BG) in the extrudates, with samples processed at 15% moisture (lowest) and 21% moisture (highest) having the highest concentration of WE-BG. After the first 8h of fermentation, more WE-BG remained in fermentation media in samples processed at 15% moisture compared with the other conditions. Also, extrusion moisture significantly affected the production of acetate, butyrate, and total SCFA by the microbiota during the first 8h of fermentation. Microbiota grown on extrudates processed at 18% moisture had the highest production of acetate and total SCFA, whereas bacteria grown on extrudates processed at 15% and 18% moisture had the highest butyrate production. After 24h of fermentation, samples processed at 15% moisture supported lower Bifidobacterium counts than those produced at other conditions, but had among the highest Lactobacillus counts. Thus, moisture content during extrusion significantly affects production of fermentation metabolites by the gut microbiota during the initial stages of fermentation, while also affecting probiotic bacteria counts during extended fermentation.