Boosting the value of insoluble dietary fiber to increase gut fermentability through food processing

Approach to the diagnosis and management of dysbiosis

All microorganisms like bacteria, viruses and fungi that reside within a host environment are considered a microbiome. The number of bacteria almost equal that of human cells, however, the genome of these bacteria may be almost 100 times larger than the human genome. Every aspect of the physiology and health can be influenced by the microbiome living in various parts of our body. Any imbalance in the microbiome composition or function is seen as dysbiosis. Different types of dysbiosis are seen and the corresponding symptoms depend on the site of microbial imbalance. The contribution of the intestinal and extra-intestinal microbiota to influence systemic activities is through interplay between different axes. Whole body dysbiosis is a complex process involving gut microbiome and non-gut related microbiome. It is still at the stage of infancy and has not yet been fully understood. Dysbiosis can be influenced by genetic factors, lifestyle habits, diet including ultra-processed foods and food additives, as well as medications. Dysbiosis has been associated with many systemic diseases and cannot be diagnosed through standard blood tests or investigations. Microbiota derived metabolites can be analyzed and can be useful in the management of dysbiosis. Whole body dysbiosis can be addressed by altering lifestyle factors, proper diet and microbial modulation. The effect of these interventions in humans depends on the beneficial microbiome alteration mostly based on animal studies with evolving evidence from human studies. There is tremendous potential for the human microbiome in the diagnosis, treatment, and prognosis of diseases, as well as, for the monitoring of health and disease in humans. Whole body system-based approach to the diagnosis of dysbiosis is better than a pure taxonomic approach. Whole body dysbiosis could be a new therapeutic target in the management of various health conditions.

Gut Microbiota and Blood Metabolites Related to Fiber Intake and Type 2 Diabetes

BACKGROUND

Consistent evidence suggests diabetes-protective effects of dietary fiber intake. However, the underlying mechanisms, particularly the role of gut microbiota and host circulating metabolites, are not fully understood. We aimed to investigate gut microbiota and circulating metabolites associated with dietary fiber intake and their relationships with type 2 diabetes (T2D).

METHODS

This study included up to 11 394 participants from the HCHS/SOL (Hispanic Community Health Study/Study of Latinos). Diet was assessed with two 24-hour dietary recalls at baseline. We examined associations of dietary fiber intake with gut microbiome measured by shotgun metagenomics (350 species/85 genera and 1958 enzymes; n=2992 at visit 2), serum metabolome measured by untargeted metabolomics (624 metabolites; n=6198 at baseline), and associations between fiber-related gut bacteria and metabolites (n=804 at visit 2). We examined prospective associations of serum microbial-associated metabolites (n=3579 at baseline) with incident T2D over 6 years.

RESULTS

We identified multiple bacterial genera, species, and related enzymes associated with fiber intake. Several bacteria (eg, Butyrivibrio, Faecalibacterium) and enzymes involved in fiber degradation (eg, xylanase EC3.2.1.156) were positively associated with fiber intake, inversely associated with prevalent T2D, and favorably associated with T2D-related metabolic traits. We identified 159 metabolites associated with fiber intake, 47 of which were associated with incident T2D. We identified 18 of these 47 metabolites associated with the identified fiber-related bacteria, including several microbial metabolites (eg, indolepropionate and 3-phenylpropionate) inversely associated with the risk of T2D. Both Butyrivibrio and Faecalibacterium were associated with these favorable metabolites. The associations of fiber-related bacteria, especially Faecalibacterium and Butyrivibrio, with T2D were attenuated after further adjustment for these microbial metabolites.

CONCLUSIONS

Among United States Hispanics/Latinos, dietary fiber intake was associated with favorable profiles of gut microbiota and circulating metabolites for T2D. These findings advance our understanding of the role of gut microbiota and microbial metabolites in the relationship between diet and T2D.

Buckwheat (Fagopyrum esculentum) Hulls Are a Rich Source of Fermentable Dietary Fibre and Bioactive Phytochemicals

Pseudo-cereals such as buckwheat (Fagopyrum esculentum) are valid candidates to promote diet biodiversity and nutrition security in an era of global climate change. Buckwheat hulls (BHs) are currently an unexplored source of dietary fibre and bioactive phytochemicals. This study assessed the effects of several bioprocessing treatments (using enzymes, yeast, and combinations of both) on BHs' nutrient and phytochemical content, their digestion and metabolism in vitro (using a gastrointestinal digestion model and mixed microbiota from human faeces). The metabolites were measured using targeted LC-MS/MS and GC analysis and 16S rRNA gene sequencing was used to detect the impact on microbiota composition. BHs are rich in insoluble fibre (31.09 ± 0.22% as non-starch polysaccharides), protocatechuic acid (390.71 ± 31.72 mg/kg), and syringaresinol (125.60 ± 6.76 mg/kg). The bioprocessing treatments significantly increased the extractability of gallic acid, vanillic acid, p-hydroxybenzoic acid, syringic acid, vanillin, syringaldehyde, p-coumaric acid, ferulic acid, caffeic acid, and syringaresinol in the alkaline-labile bound form, suggesting the bioaccessibility of these phytochemicals to the colon. Furthermore, one of the treatments, EC_2 treatment, increased significantly the in vitro upper gastrointestinal release of bioactive phytochemicals, especially for protocatechuic acid (p < 0.01). The BH fibre was fermentable, promoting the formation mainly of propionate and, to a lesser extent, butyrate formation. The EM_1 and EC_2 treatments effectively increased the content of insoluble fibre but had no effect on dietary fibre fermentation (p > 0.05). These findings promote the use of buckwheat hulls as a source of dietary fibre and phytochemicals to help meet dietary recommendations and needs.

Relationship between Physicochemical, Techno-Functional and Health-Promoting Properties of Fiber-Rich Fruit and Vegetable By-Products and Their Enhancement by Emerging Technologies

The preparation and processing of fruits and vegetables produce high amounts of underutilized fractions, such as pomace and peel, which present a risk to the environment but constitute a valuable source of dietary fiber (DF) and bioactive compounds. The utilization of these fiber-rich products as functional food ingredients demands the application of treatments to improve their techno-functional properties, such as oil and water binding, and health-related properties, such as fermentability, adsorption, and retardation capacities of glucose, cholesterol, and bile acids. The enhancement of health-promoting properties is strongly connected with certain structural and techno-functional characteristics, such as the soluble DF content, presence of hydrophobic groups, and viscosity. Novel physical, environmentally friendly technologies, such as ultrasound (US), high-pressure processing (HPP), extrusion, and microwave, have been found to have higher potential than chemical and comminution techniques in causing desirable structural alterations of the DF network that lead to the improvement of techno-functionality and health promotion. The application of enzymes was related to higher soluble DF content, which might be associated with improved DF properties. Combined physical and enzymatic treatments can aid solubilization and modifications, but their benefit needs to be evaluated for each DF source and the desired outcome.

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.

Novel processing strategies to enhance the bioaccessibility and bioavailability of functional components in wheat bran

Dietary fiber, polysaccharides and phenols are the representative functional components in wheat bran, which have important nutritional properties and pharmacological effects. However, the most functional components in wheat bran exist in bound form with low bioaccessibility. This paper reviews these functional components, analyzes modification methods, and focuses on novel solid-state fermentation (SSF) strategies in the release of functional components. Mining efficient microbial resources from traditional fermented foods, exploring the law of material exchange between cell populations, and building a stable self-regulation co-culture system are expected to strengthen the SSF process. In addition, emerging biotechnology such as synthetic biology and genome editing are used to transform the mixed fermentation system. Furthermore, combined with the emerging physical-field pretreatment coupled with SSF strategies applied to the modification of wheat bran, which provides a theoretical basis for the high-value utilization of wheat bran and the development of related functional foods and drugs.

Effect of drying method on the production of in vitro short-chain fatty acids and histone deacetylase mediation of cocoa pod husk

We evaluated the effect of cocoa pod husk (CPH) processing (microwave [MW], forced-air drying [FAD], and FAD plus extrusion [FAD-E]), and in vitro gastrointestinal digestion on the in vitro human colonic fermentation metabolism, in vitro bioactivity on human HT-29 colon cancer cell, and the in silico mechanism of selected compounds. CPH as a substrate for human colonic microbiota significantly decrease local pH (MW -0.7, FAD -0.2, and FAD-E -0.3, 24 h) and modifies their metabolic activity (short-chain fatty acids [SCFAs] production). FAD-E generated the highest butyric (7.6 mM/L, 4 h) and FAD the highest acetic and propionic acid levels (71.4 and 36.7 mM/L, 24 h). The in vitro colonic fermented FAD-E sample (FE/FAD-E) caused HT-29 colorectal cancer cells death by inducing damage on membrane integrity and inhibiting (up to 92%) histone-deacetylase (HDAC) activity. In silico results showed that chlorogenic acid, (-)-epicatechin, and (+)-catechin, followed by butyric and propionic acids, are highly involved in the HDAC6 inhibitory activity. The results highlight the potential human health postbiotic benefits of CPH consumption, mediated by colonic microbiota-derived metabolites. PRACTICAL APPLICATION: The enormous amount of CPH (10 tons/1 ton of dry beans) generated by the cocoa industry can be used as a removable source of bioactive compounds with physicochemical functionality and health bioactivity. However, their potential applications and health benefits are insufficiently explored. CPH represents a serious disposal problem; practical and innovative ideas to use this highly available and affordable material are urgent. Research exploring their potential applications can increase the sustainability of the cocoa agro-industry. This paper highlights the value addition that can be achieved with this valuable industrial co-product, generating new functional products and ingredients.

Insoluble dietary fibers: structure, metabolism, interactions with human microbiome, and role in gut homeostasis

Consumption of food rich in dietary fibers (DFs) has been long recognized to exert an overall beneficial effect on human health. This review aims to provide a holistic overview on how IDFs impact human gut health either directly, or through modulation of the gut microbiome. Several databases were searched for collecting papers such as PubMed, Google Scholar, Web of Science, Scopus and Reaxys from 2000 till 2022. Firstly, an overview of the chemical structure of the various IDFs and the pathways employed by gut microbiota for their degradation is provided. The impact of IDFs on microbial community structure and pathogens colonization inside the human gut was discussed. Finally, the impact of IDFs on gut homeostasis and systemic effects at the cellular level, as well as the overall immunological benefits of IDFs consumption were analyzed. IDFs viz., cellulose, hemicellulose, resistant starch, and lignin found enriched in food are discussed for these effects. IDFs were found to induce gut immunity, improve intestinal integrity and mucosal proliferation, and favor adhesion of probiotics and hence improve human health. Also, IDFs were concluded to improve the bioavailability of plant polyphenols and improve their health-related functional roles. Ultimately, dietary fibers processing by modification shows potential to enhance fibers-based functional food production, in addition to increase the economic value and usage of food-rich fibers and their by-products.