In vitro Colon Fermentation of Soluble Arabinoxylan Is Modified Through Milling and Extrusion

Prebiotic potential of oligosaccharides extracted from improved Ugandan varieties of millet, sesame, soybean, and sorghum: enhancing probiotic growth and enteric pathogen inhibition

Functional gastrointestinal disorders like diarrhea continue to affect children under five years in low-income countries. Incorporating health-enhancing bioactive compounds such as prebiotics in diet offers a promising solution. This study investigated prebiotic potential of oligosaccharides extracted from improved varieties of millet (Seremi 2, Naromil 2), sesame (Sesim 2, Sesim 3), soybean (Maksoy 3N, Maksoy 6N), and sorghum (Narosorg 2, Narosorg 4), commonly consumed in Uganda. These were compared to their respective indigenous variety. This study employed standardized methods for optical density measurement, culture preparation, and oligosaccharide extraction to evaluate prebiotic properties. We investigated whether plant-based oligosaccharides could enhance the effectiveness of probiotics, specifically Lactiplantibacillus plantarum (ATCC 14917) and Lacticaseibacillus rhamnosus (ATCC 7469), in antagonizing common enteric pathogens (Salmonella enterica subsp. enterica (ATCC 13076) and Shigella flexneri (ATCC 12022)). Approximately 4-8 log CFU/ml of each probiotic was incubated in 2% w/v oligosaccharide extracts at 37 °C to evaluate the influence of the extracts on their growth, short-chain fatty acid (SCFA) production and antagonistic activity. Maximum cell density, which exceeded the minimum recommended probiotic cell density (6 log CFU/ml), was achieved during 24-h incubation period. The probiotics exhibited optimal growth in extracts of Sesim 2, Maksoy 3N, Narosorg 2 and indigenous millet variety resulting in a 68-84% increase in cell densities. The concentration of SCFA concentration was significantly higher (p < 0.05) in soybean-based oligosaccharides. Both probiotics antagonized growth of Salmonella and Shigella by more than 40% when cultured on Sesim 2, Maksoy 3N, Narosorg 2 and indigenous millet variety, while maintaining the probiotic cell densities above the minimum recommended level. These varieties show great potential as functional ingredients for developing synbiotic-rich foods to promote gut and public health. However, to evaluate the oligosaccharides prebiotic efficacy, in vitro fermentation using fecal microbiota and in vivo studies are necessary to determine gut microbiota changes and interactions.

Wheat arabinoxylans: Insight into structure-function relationships

Arabinoxylan (AX), a key non-starch polysaccharide found in the cell walls of cereals like wheat, holds significant importance in the food industry. Recently, it has attracted attention due to its numerous health benefits. While the benefits of wheat arabinoxylans are well-established, a more comprehensive understanding of the relationship between their structure and functional properties is essential. This knowledge will be instrumental in addressing potential concerns in future research focusing on food products containing wheat arabinoxylan. Previous reviews predominantly focused on cereal arabinoxylans, and only a few have addressed wheat arabinoxylan. This review aims to consolidate recent research findings on wheat arabinoxylans, highlighting their health benefits and potential links to structural variations. This will aid future studies in this area. Feruloylated arabinoxylans and arabinoxylan oligosaccharides stand out as the most known for their health benefits. Modifying the chemical structure of arabinoxylans to yield low molecular weight oligosaccharides enhances their immunomodulatory and antioxidant activities, as well as promotes the growth and availability of beneficial gut microbes. The antioxidant activity is positively correlated with the ferulic acid content, whereas it has a negative correlation with arabinose substitution. Nevertheless, additional research using final products is necessary to delve into the potential underlying mechanisms.

Advances in understanding dietary fiber: Classification, structural characterization, modification, and gut microbiome interactions

Gut microbiota and their metabolites profoundly impact host physiology. Targeted modulation of gut microbiota has been a long-term interest in the scientific community. Numerous studies have investigated the feasibility of utilizing dietary fibers (DFs) to modulate gut microbiota and promote the production of health-beneficial bacterial metabolites. However, the complexity of fiber structures, microbiota composition, and their dynamic interactions have hindered the precise prediction of the impact of DF on the gut microbiome. We address this issue with a new perspective, focusing on the inherent chemical and structural complexity of DFs and their interaction with gut microbiota. The chemical and structural complexity of fibers was thoroughly elaborated, encompassing the fibers' molecular composition, polymorphism, mesoscopic structures, porosity, and particle size. Advanced characterization techniques to investigate fiber structural properties were discussed. Additionally, we examined the interactions between DFs and gut microbiota. Finally, we summarized processing techniques to modify fiber structures for improving the fermentability of DF by gut microbiota. The structure of fibers, such as their crystallinity, porosity, degree of branching, and pore wettability, significantly impacts their interactions with gut microbiota. These structural differences also substantially affect fiber's fermentability and capability to modulate the composition of gut microbiota. Conventional approaches are not capable of investigating complex fiber properties and their influences on the gut microbiome; therefore, it is of the essence to involve advanced material characterization techniques and artificial intelligence to unveil more comprehensive information on this topic.

Combination of Inulin and Resistant Dextrin Has Superior Prebiotic Effects and Reduces Gas Production During In Vitro Fermentation of Fecal Samples from Older People

BACKGROUND

Older people are more susceptible to deterioration of the gut microbiota. Prebiotics help improve the gut microbiota. Inulin, a major prebiotic, stimulates the growth of Bifidobacterium; however, it produces a large amount of gas, which leads to abdominal symptoms.

METHODS

In this study, in vitro fecal fermentation was performed using fecal samples from seven older people (mean subject age, 73.4 years; five men and two women) to examine whether combining inulin with another prebiotic material, resistant dextrin, could lead to decreased gas production and show prebiotic effects.

RESULTS

The Bifidobacterium counts and short-chain fatty acid production did not differ significantly between the inulin 0.5% group and the inulin 0.25% plus resistant dextrin 0.25% combination group. However, the inulin 0.25% plus resistant dextrin 0.25% combination group had lower gas production than the inulin 0.5% group (p < 0.10). Furthermore, compared with the inulin 0.5% group, the 0.25% combination group showed significantly greater gut microbiota diversity and tended toward a lower pH in the fermentation medium at the end of fermentation (p = 0.09). These effects are believed to be due to the combination of inulin, which is highly selective for Bifidobacterium and rapidly utilized by the gut microbiota, and resistant dextrin, which is slowly utilized by various bacterial genera.

CONCLUSIONS

These findings suggest that the inulin plus resistant dextrin combination has superior prebiotic effects in older people and causes less gas production than inulin alone.

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.

Dietary fiber and polyphenols from whole grains: effects on the gut and health improvements

Cereals are the main source of energy in the human diet. Compared to refined grains, whole grains retain more beneficial components, including dietary fiber, polyphenols, proteins, vitamins, and minerals. Dietary fiber and bound polyphenols (biounavailable) in cereals are important active substances that can be metabolized by the gut microorganisms and affect the intestinal environment. There is a close relationship between the gut microbiota structures and various disease phenotypes, although the consistency of this link is affected by many factors, and the specific mechanisms are still unclear. Remodeling unfavorable microbiota is widely recognized as an important way to target the gut and improve diseases. This paper mainly reviews the interaction between the gut microbiota and cereal-derived dietary fiber and polyphenols, and also summarizes the changes to the gut microbiota and possible molecular mechanisms of related glycolipid metabolism. The exploration of single active ingredients in cereals and their synergistic health mechanisms will contribute to a better understanding of the health benefits of whole grains. It will further help promote healthier whole grain foods by cultivating new varieties with more potential and optimizing processing methods.

Bioengineered Wheat Arabinoxylan - Fostering Next-Generation Prebiotics Targeting Health-Related Gut Microbes

Dietary prebiotic fibers play an important role in modulating gut microbiota by enhancing the abundance of beneficial microorganisms and their bioactive metabolites. However, dietary fibers are a structurally heterogeneous class of polysaccharides, varying in molar mass, branching patterns, and monosaccharide composition, which could influence their utilization by various gut microorganisms. The present study aimed to investigate the effects of molar mass and chemical structure of wheat arabinoxylan fiber (AX) on the growth and metabolism of two key gut resident bacteria (Faecalibacterium prausnitzii and Lacticaseibacillus rhamnosus LGG), which are linked to human health. For this purpose, low, medium, and high molar masses of AX (LAX, MAX, and HAX, respectively) were modified with specific α-arabinofuranosidases to leave only singly substituted, only doubly substituted, or unsubstituted xylose units. Almost all the modified AX samples showed a better prebiotic score than unmodified AX for different molar masses. The modified LAX exhibited a better prebiotic effect than HAX and MAX. In addition, LAX, with doubly substituted xylose units, exhibited the highest prebiotic potential and SCFA production by both microorganisms. Furthermore, AX, either singly or doubly substituted, had a consistent impact on L. rhamnosus growth, whereas AX, with all arabinose residues removed, had a greater impact on F. prausnitzii. These findings support the potential of bioengineered AX as next-generation prebiotics targeting health-related gut microbes.

Arabinoxylan source and xylanase specificity influence the production of oligosaccharides with prebiotic potential

Cereal arabinoxylans (AXs) are complex polysaccharides in terms of their pattern of arabinose and ferulic acid substitutions, which influence their properties in structural and nutritional applications. We have evaluated the influence of the molecular structure of three AXs from wheat and rye with distinct substitutions on the activity of β-xylanases from different glycosyl hydrolase families (GH 5_34, 8, 10 and 11). The arabinose and ferulic acid substitutions influence the accessibility of the xylanases, resulting in specific profiles of arabinoxylan-oligosaccharides (AXOS). The GH10 xylanase from Aspergillus aculeatus (AcXyn10A) and GH11 from Thermomyces lanuginosus (TlXyn11) showed the highest activity, producing larger amounts of small oligosaccharides in shorter time. The GH8 xylanase from Bacillus sp. (BXyn8) produced linear xylooligosaccharides and was most restricted by arabinose substitution, whereas GH5_34 from Gonapodya prolifera (GpXyn5_34) required arabinose substitution and produced longer (A)XOS substituted on the reducing end. The complementary substrate specificity of BXyn8 and GpXyn5_34 revealed how arabinoses were distributed along the xylan backbones. This study demonstrates that AX source and xylanase specificity influence the production of oligosaccharides with specific structures, which in turn impacts the growth of specific bacteria (Bacteroides ovatus and Bifidobacterium adolescentis) and the production of beneficial metabolites (short-chain fatty acids).

Effects of Co-Modification by Extrusion and Enzymatic Hydrolysis on Physicochemical Properties of Black Wheat Bran and Its Prebiotic Potential

Black wheat bran (BWB) is an important source of dietary fiber (DF) and phenolic compounds and has stronger nutritional advantages than ordinary WB. However, the low content of soluble dietary fiber (SDF) negatively influences its physicochemical properties and nutritive functions. To obtain a higher content of SDF in BWB, we evaluated the impact of co-modification by extrusion and enzymes (cellulase, xylanase, high-temperature α-amylase, and acid protease) on water extractable arabinoxylan (WEAX) in BWB. An optimized co-modification method was obtained through single-factor and orthogonal experiments. The prebiotic potential of co-modified BWB was also evaluated using pooled fecal microbiota from young, healthy volunteers. The commonly investigated inulin served as a positive control. After co-modification, WEAX content was dramatically increased from 0.31 g/100 g to 3.03 g/100 g (p < 0.05). The water holding capacity, oil holding capacity, and cholesterol adsorption capacity (pH = 2.0 and pH = 7.0) of BWB were increased by 100%, 71%, 131%, and 133%, respectively (p < 0.05). Scanning electron microscopy demonstrated a looser and more porous microstructure for co-modified BWB granules. Through in vitro anerobic fermentation, co-modified BWB achieved a higher content of Bifidobacterium and Lactobacillus than inulin fermentation. In addition, co-modified BWB induced the highest butyric acid production, indicating high potential as prebiotics. The results may contribute to improving technologies for developing high-fiber-content cereal products.

Intestinal permeability and gut microbiota interactions of pharmacologically active compounds in valerian and St. John's wort

Phytomedicines such as valerian and St. John's wort are widely used for the treatment of sleeping disorders, anxiety and mild depression. They are perceived as safe alternatives to synthetic drugs, but limited information is available on the intestinal absorption and interaction with human intestinal microbiota of pharmacologically relevant constituents valerenic acid in valerian, and hyperforin and hypericin in St. John's wort. The intestinal permeability of these compounds and the antidepressant and anxiolytic drugs citalopram and diazepam was investigated in the Caco-2 cell model with bidirectional transport experiments. In addition, interaction of compounds and herbal extracts with intestinal microbiota was evaluated in artificial human gut microbiota. Microbiota-mediated metabolisation of compounds was assessed, and bacterial viability and short-chain fatty acids (SCFA) production were measured in the presence of compounds or herbal extracts. Valerenic acid and hyperforin were highly permeable in Caco-2 cell monolayers. Hypericin showed low-to-moderate permeability. An active transport process was potentially involved in the transfer of valerenic acid. Hyperforin and hypericin were mainly transported through passive transcellular diffusion. All compounds were not metabolized over 24 h in the artificial gut microbiota. Microbial SCFA production and bacterial viability was not substantially impaired nor promoted by exposure to the compounds or herbal extracts.

In vitro human gut microbiota fermentation models: opportunities, challenges, and pitfalls

The human gut microbiota (HGM) plays a pivotal role in health and disease. Consequently, nutritional and medical research focusing on HGM modulation strategies as a means of improving host health is steadily increasing. In vitro HGM fermentation models offer a valid complement to human and animal studies when it comes to the mechanistic exploration of novel modulation approaches and their direct effects on HGM composition and activity, while excluding interfering host effects. However, in vitro cultivation of HGM can be challenging due to its high oxygen sensitivity and the difficulties of accurately modeling the physio-chemical complexity of the gut environment. Despite the increased use of in vitro HGM models, there is no consensus about appropriate model selection and operation, sometimes leading to major deficiencies in study design and result interpretation. In this review paper, we aim to analyze crucial aspects of the application, setup and operation, data validation and result interpretation of in vitro HGM models. When carefully designed and implemented, in vitro HGM modeling is a powerful strategy for isolating and investigating biotic and abiotic factors in the HGM, as well as evaluating their effects in a controlled environment akin to the gut. Furthermore, complementary approaches combining different in vitro and in vivo models can strengthen the design and interpretation of human studies.

A single administration of barley β-glucan and arabinoxylan extracts reduces blood glucose levels at the second meal via intestinal fermentation

Diet with barley may suppress the glycemic response after consuming the next meal ("second meal effect"). This study aimed to investigate the second meal effect and its mechanism. Mice were given a single dose of β-glucan or arabinoxylan, the primary sources of soluble fiber in barley. A single dose of β-glucan or arabinoxylan extract, followed 6 h later by a 20% glucose solution (second meal), suppressed blood glucose elevation. Arabinoxylan and β-glucan increased the levels of short-chain fatty acids (SCFAs) in the ileum and cecum, respectively. Total GLP-1 secretion in the blood increased with β-glucan and showed an increasing trend with arabinoxylan. These results suggest barley β-glucan and arabinoxylan are fermented in the intestinal tract to generate SCFAs, which may induce GLP-1 secretion and control blood glucose levels during the second meal.

Recent advances in developing butyrogenic functional foods to promote gut health

As one of the major short-chain fatty acids produced via microbial fermentation, butyrate serves as not only a preferred energy substrate but also an important signaling molecule. Butyrate concentrations in circulation, tissues, and gut luminal contents have important pathophysiological implications. The genetic capacity of butyrate biosynthesis by the gut microbiota is frequently compromised during aging and various disorders, such as inflammatory bowel disease, metabolic disorders and colorectal cancer. Substantial efforts have been made to identify potent butyrogenic substrates and butyrate-hyperproducing bacteria to compensate for butyrate deficiency. Interindividual butyrogenic responses exist, which are more strongly predicted by heterogeneity in the gut microbiota composition than by ingested prebiotic substrates. In this review, we catalog major food types rich in butyrogenic substrates. We also discuss the potential of butyrogenic foods with proven properties for promoting gut health and disease management using findings from clinical trials. Potential limitations and constraints in the current research are highlighted. We advocate a precise nutrition approach in designing future clinical trials by prescreening individuals for key gut microbial signatures when recruiting study volunteers. The information provided in this review will be conducive to the development of microbiota engineering approaches for enhancing the sustained production of butyrate.