Effect of chito-oligosaccharides over human faecal microbiota during fermentation in batch cultures

An Update on Prebiotics and on Their Health Effects

Prebiotic compounds were originally defined as "a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health"; however, a significant modulation of the definition was carried out in the consensus panel of The International Scientific Association for Probiotics and Prebiotics (ISAPP), and the last definition states that "prebiotics are substrates that are selectively utilized by host microorganisms conferring a health benefit". Health effects of prebiotics compounds attracted the interest of researchers, food companies and Regulatory Agencies, as inferred by the number of articles on Scopus for the keywords "prebiotic" and "health effects", that is ca. 2000, for the period January 2021-January 2024. Therefore, the aim of this paper is to contribute to the debate on these topics by offering an overview of existing knowledge and advances in this field. A literature search was performed for the period 2012-2023 and after the selection of the most relevant items, the attention was focused on seven conditions for which at least 8-10 different studies were found, namely colorectal cancer, neurological or psychiatric conditions, intestinal diseases, obesity, diabetes, metabolic syndrome, and immune system disorders. In addition, the analysis of the most recent articles through the software VosViewer version 1.6.20 pointed out the existence of five clusters or macro-categories, namely: (i) pathologies; (ii) metabolic condvitions; (iii) structure and use in food; (iv) immunomodulation; (v) effect on gut microbiota.

N-acetyl-d-glucosamine-based oligosaccharides from chitin: Enzymatic production, characterization and biological activities

Chitin, the second most abundant biopolymer, possesses diverse applications in the food, agricultural, and pharmaceutical industries due to its functional properties. However, the potential applications of chitin are limited owing to its high crystallinity and low solubility. N-acetyl chitooligosaccharides and lacto-N-triose II, the two types of GlcNAc-based oligosaccharides, can be obtained from chitin by enzymatic methods. With their lower molecular weights and improved solubility, these two types of GlcNAc-based oligosaccharides display more various beneficial health effects when compared to chitin. Among their abilities, they have exhibited antioxidant, anti-inflammatory, anti-tumor, antimicrobial, and plant elicitor activities as well as immunomodulatory and prebiotic effects, which suggests they have the potential to be utilized as food additives, functional daily supplements, drug precursors, elicitors for plants, and prebiotics. This review comprehensively covers the enzymatic methods used for the two types of GlcNAc-based oligosaccharides production from chitin by chitinolytic enzymes. Moreover, current advances in the structural characterization and biological activities of these two types of GlcNAc-based oligosaccharides are summarized in the review. We also highlight current problems in the production of these oligosaccharides and trends in their development, aiming to offer some directions for producing functional oligosaccharides from chitin.

The function of human milk oligosaccharides and their substitute oligosaccharides as probiotics in gut inflammation

Gut inflammation seriously affects the healthy life of patients, and has a trend of increasing incidence rate. However, the current methods for treating gut inflammation are limited to surgery and drugs, which can cause irreversible damage to patients, especially infants. As natural oligosaccharides in human breast milk, human milk oligosaccharides (HMOs) function as probiotics in treating and preventing gut inflammation: improving the abundance of the gut microbiota, increasing the gut barrier function, and reducing the gut inflammatory reaction. Meanwhile, due to the complexity and high cost of their synthesis, people are searching for functional oligosaccharides that can replace HMOs as a food additive in infants milk powder and adjuvant therapy for chronic inflammation. The purpose of this review is to summarize the therapeutic and preventive effects of HMOs and their substitute functional oligosaccharides as probiotics in gut inflammation, and to summarize the prospect of their application in infant breast milk replacement in the future.

Anti-Obesity Effect and Mechanism of Chitooligosaccharides Were Revealed Based on Lipidomics in Diet-Induced Obese Mice

Chitooligosaccharide (COS) is a natural product from the ocean, and while many studies have reported its important role in metabolic diseases, no study has systematically elaborated the anti-obesity effect and mechanism of COS. Herein, COSM (MW ≤ 3000 Da) was administered to diet-induced obese mice by oral gavage once daily for eight weeks. The results show that COSM administration reduced body weight; slowed weight gain; reduced serum Glu, insulin, NEFA, TC, TG, and LDL-C levels; increased serum HSL and HDL-C levels; improved inflammation; and reduced lipid droplet size in adipose tissue. Further lipidomic analysis of adipose tissue revealed that 31 lipid species are considered to be underlying lipid biomarkers in COS therapy. These lipids are mainly enriched in pathways involving insulin resistance, thermogenesis, cholesterol metabolism, glyceride metabolism and cyclic adenosine monophosphate (cAMP), which sheds light on the weight loss mechanism of COS. The Western blot assay demonstrated that COSM intervention can improve insulin resistance, inhibit de novo synthesis, and promote thermogenesis and β-oxidation in mitochondria by the AMPK pathway, thereby alleviating high-fat diet-induced obesity. In short, our study can provide a more comprehensive direction for the application of COS in obesity based on molecular markers.

Insights into the relationships of modifying methods, structure, functional properties and applications of chitin: A review

Chitin as the second plentiful polysaccharide has arouse widely attention due to its remarkable availability and biocompatibility. While the strong inter/intra molecular hydrogen bonds and crystallinity severely restrict its applications. Recently, multiple emerging technologies are increasingly used to modify chitin structure for the sake of obtaining excellent functional properties, as well as broadening the corresponding applications. Firstly, this review systematically outlines the features of single and combined methods for chitin modification. Then, the impacts of various modifying methods on the structural characteristics of chitin, including molecular weight, degree of acetylation and functional groups, are further summarized. In addition, the effects of these structural characteristics on the functional properties as well as its potential related applications are illustrated. The conclusion of this review provides better understanding of the relationships among the modifying methods, structure, properties and applications, contributing to chitin modification for the targeted purpose in the future study.

Chitosan Enhances Intestinal Health in Cats by Altering the Composition of Gut Microbiota and Metabolites

The interaction between gut microbiota and the health of the host has gained increasing attention. Chitosan is a natural alkaline polysaccharide with a wide range of beneficial effects. However, rare studies have been observed on the effects of dietary chitosan supplementation on intestinal health in cats. A total of 30 cats with mild diarrhea were divided into three groups, receiving a basic diet with 0 (CON), 500 (L-CS) or 2000 (H-CS) mg/kg chitosan. Samples of blood and feces were collected and analyzed for serology and gut microbiota composition. The results demonstrated that chitosan alleviated symptoms of diarrhea, with enhanced antioxidant capability and decreased inflammatory biomarker levels in serum. Chitosan reshaped the composition of gut microbiota in cats that the beneficial bacteria Allobaculum was significantly increased in the H-CS group. Acetate and butyrate contents in feces were significantly higher in the H-CS group in comparison to the CON group (p < 0.05). In conclusion, the addition of dietary chitosan in cats enhanced intestinal health by modulating their intestinal microbes and improved microbiota-derived SCFA production. Our results provided insights into the role of chitosan in the gut microbiota of felines.

Chitin and omega-3 fatty acids in edible insects have underexplored benefits for the gut microbiome and human health

A healthy gut microbiome is critical for nutrient metabolism, pathogen inhibition and immune regulation, and is highly influenced by diet. Edible insects are good sources of protein and micronutrients, but unlike other animal-derived foods, they also contain both dietary fibre and omega-3 fatty acids that can modulate gut microbiota. Here we explore the potential impacts of insect consumption on the microbiome. Laboratory, animal and human studies indicate that insect fibre in the form of chitin and its derivatives can modify gut microbiota with beneficial outcomes. Some insects also contain favourable omega-3/omega-6 ratios. We identify gaps in the literature-especially a dearth of human studies-that must be addressed to better understand health impacts of entomophagy. Insects, already eaten across the globe, can be farmed using fewer resources than conventional livestock. Widening the research scope offers an opportunity to advance use of edible insects to address interconnected environmental and health challenges.

Effects of in vitro digestion and fecal fermentation on physico-chemical properties and metabolic behavior of polysaccharides from Clitocybe squamulosa

The aim of this study was to establish a human digestion model in vitro to explore the degradation characteristics of a novel high-purity polysaccharide from Clitocybe squamulosa (CSFP2). The results showed that the content of reducing sugars (C_R ) of CSFP2 increased from 0.13 to 0.23 mg/mL, the molecular weight (Mw) of CSFP2 decreased significantly during the saliva-gastrointestinal digestion. The constituent monosaccharides of CSFP2, including galactose, glucose, and mannose, were stable during in vitro digestion, but their molar ratios were changed from 0.023: 0.737: 0.234 to 0.496: 0.478: 0.027. The surface of CSFP2 changes from a rough flaky structure to a scattered flocculent or rod-shaped structure after the gastrointestinal digestion. However, the apparent viscosity of CSFP2 was overall stable during in vitro digestion. Moreover, CSFP2 still maintains its strong antioxidant capacity after saliva-gastrointestinal digestion. The results showed that CSFP2 can be partially decomposed during digestion. Meanwhile, some physico-chemical properties of the fermentation broth containing CSFP2 changed significantly after gut microbiota fermentation. For example, the pH value (from 8.46 to 4.72) decreased significantly (p < 0.05) after 48 h of fermentation. the OD ₆₀₀ value increased first and then decreased (from 2.00 to 2.68 to 1.32) during 48-h fermentation. In addition, CSFP2 could also increase the amounts of short-chain fatty acids (SCFAs) (from 5.5 to 37.15 mmol/L) during fermentation (in particular, acetic acid, propionic acid, and butyric acid). Furthermore, the relative abundances of Bacteriodes, Bifidobacterium, Catenibacterium, Lachnospiraceae_NK4A136_group, Megasphaera, Prevotella, Megamonas, and Lactobacillus at genus level were markedly increased with the intervention of CSFP2. These results provided a theoretical basis for the further development of functional foods related to CSFP2.

Biologically Active Supplements Affecting Producer Microorganisms in Food Biotechnology: A Review

Microorganisms, fermentation processes, and the resultant metabolic products are a key driving force in biotechnology and, in particular, in food biotechnology. The quantity and/or quality of final manufactured food products are directly related to the efficiency of the metabolic processes of producer microorganisms. Food BioTech companies are naturally interested in increasing the productivity of their biotechnological production lines. This could be achieved via either indirect or direct influence on the fundamental mechanisms governing biological processes occurring in microbial cells. This review considers an approach to improve the efficiency of producer microorganisms through the use of several types of substances or complexes affecting the metabolic processes of microbial producers that are of interest for food biotechnology, particularly fermented milk products. A classification of these supplements will be given, depending on their chemical nature (poly- and oligosaccharides; poly- and oligopeptides, individual amino acids; miscellaneous substances, including vitamins and other organic compounds, minerals, and multicomponent supplements), and the approved results of their application will be comprehensively surveyed.

Impact of inorganic iron and haem on the human gut microbiota; An in vitro batch-culture approach

Although iron is an essential nutrient for humans, as well as for almost all other organisms, it is poorly absorbed (~15%) from the diet such that most passes through the upper gut into the large intestine. The colonic microbiota is thus exposed to, and potentially influenced by, such residual iron which could have an impact on human health. The aim of the research described here is to determine how the major forms of dietary iron (inorganic iron and haem) influence metabolic activity and composition of the human gut microbiota by utilizing an in vitro parallel, pH-controlled anaerobic batch culture approach. Controlled iron provision was enabled by the design of a 'modified' low-iron gut-model medium whereby background iron content was reduced from 28 to 5 μM. Thus, the impact of both low and high levels of inorganic and haem iron (18-180 μM and 7.7-77 μM, respectively) could be explored. Gut-microbiota composition was determined using next generation sequencing (NGS) based community profiling (16S rRNA gene sequencing) and flow-fluorescent in situ hybridization (FISH). Metabolic-end products (organic acids) were quantified using gas chromatography (GC) and iron incorporation was estimated by inductively coupled plasma optical emission spectroscopy (ICP-OES). Results showed that differences in iron regime induced significant changes in microbiota composition when low (0.1% w/v) fecal inoculation levels were employed. An increase in haem levels from 7.7 to 77 μM (standard levels employed in gut culture studies) resulted in reduced microbial diversity, a significant increase in Enterobacteriaceae and lower short chain fatty acid (SCFA) production. These effects were countered when 18 μM inorganic iron was also included into the growth medium. The results therefore suggest that high-dietary haem may have a detrimental effect on health since the resulting changes in microbiota composition and SCFA production are indicators of an unhealthy gut. The results also demonstrate that employing a low inoculum together with a low-iron gut-model medium facilitated in vitro investigation of the relationship between iron and the gut microbiota.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

Chitosan and Chitooligosaccharide: The Promising Non-Plant-Derived Prebiotics with Multiple Biological Activities

Biodegradable chitin is the second-most abundant natural polysaccharide, widely existing in the exoskeletons of crabs, shrimps, insects, and the cell walls of fungi. Chitosan and chitooligosaccharide (COS, also named chitosan oligosaccharide) are the two most important deacetylated derivatives of chitin. Compared with chitin, chitosan and COS not only have more satisfactory physicochemical properties but also exhibit additional biological activities, which cause them to be widely applied in the fields of food, medicine, and agriculture. Additionally, due to their significant ability to improve gut microbiota, chitosan and COS are deemed prospective prebiotics. Here, we introduced the production, physicochemical properties, applications, and pharmacokinetic characteristics of chitosan and COS. Furthermore, we summarized the latest research on their antioxidant, anti-inflammatory, and antimicrobial activities. Research progress on the prebiotic functions of chitosan and COS is particularly reviewed. We creatively analyzed and discussed the mechanisms and correlations underlying these activities of chitosan and COS and their physicochemical properties. Our work enriched people's understanding of these non-plant-derived prebiotics. Based on this review, the future directions of research on chitosan and COS are explored. Collectively, optimizing the production technology of chitin derivatives and enriching understanding of their biological functions will shed more light on their capability to improve human health.

Effects of Different Ionic Polysaccharides in Cooked Lean Pork Batters on Intestinal Health in Mice

The effects of cooked lean pork batters with three ionic types of polysaccharides (anionic xanthan-gum/sodium-alginate, neutral curdlan-gum/konjac-gum and cationic chitosan) on the intestinal health of mice were investigated in this study. The results showed that the zeta potential in the sodium-alginate group (−31.35 mV) was higher (p < 0.05) than that in the chitosan group (−26.00 mV), thus promoting the protein hydrolysis in the anionic group because of electrostatic repulsion. The content of total free amino acids in the small intestine in the xanthan-gum and sodium-alginate groups (2754.68 μg and 2733.72 μg, respectively) were higher (p < 0.05) than that in the chitosan group (1949.78 μg), which could decrease the amount of undigested protein entering the colon. The two anionic groups could also increase the abundance of Lactobacillus and the balance of Faecalibaculum and Alistipes in the colon. The content of proinflammatory factor IL−6 of colon tissues in the sodium-alginate group (1.02 ng/mL) was lower (p < 0.05) than that in chitosan, curdlan-gum and konjac-gum groups (1.29, 1.31 and 1.31 ng/mL, respectively). The result of haematoxylin-eosin staining of the colon also revealed that sodium alginate was beneficial for colonic health. The two neutral groups increased the content of faecal short-chain fatty acids in mice. These results demonstrated that anionic polysaccharides have potential for developing functional low-fat meat products.

In vitro digestion and fermentation by human fecal microbiota of polysaccharides from Clitocybe squamulose

The present study aimed to evaluate the effects of in vitro simulated saliva-gastrointestinal digestion and fecal fermentation behavior on the chemical composition, structure and bioactivity of polysaccharides from Clitocybe squamulosa (CSFP). Results showed that gastric digestion significantly changed the chemical composition and structural properties of CSFP, such as total uronic acid, reducing sugar, molecular weight, rheological properties, particle size, and microscopic morphology. In particular, the molecular weight decreased from 19,480 Da to 10,945 Da, while the reducing-sugar content increased from 0.149 mg/mL to 0.293 mg/mL. Gastric digestion also affected the biological activity of CSFP. Although after gastric digestion, CSFP retained its vigorous antioxidant activity, ability to inhibit α-amylase activity, and the binding ability to bile acid, fat, and free cholesterol in vitro. However, there was an apparent weakening trend. After in vitro fermentation of gut microbiota, the content of total sugar was significantly decreased from 11.6 mg/mL to 2.4 mg/mL, and the pH value in the fecal culture significantly decreased to 5.20, indicating that CSFP could be broken down and utilized by gut microbiota. Compared to the blank, the concentrations of total short-chain fatty acids (SCFAs) including acetic, propionic and n-butyric significantly increased. Simultaneously, CSFP could remarkably reduce the proportions of Firmicutes and Bacteroides (F/B) and promote the growth of some beneficial intestinal microbiota. Therefore, CSFP can potentially be a new functional food as prebiotics to promote human gut health.

Nutraceuticals and Herbal Food Supplements for Weight Loss: Is There a Prebiotic Role in the Mechanism of Action?

Numerous nutraceuticals and botanical food supplements are used with the intention of modulating body weight. A recent review examined the main food supplements used in weight loss, dividing them according to the main effects for which they were investigated. The direct or indirect effects exerted on the intestinal microbiota can also contribute to the effectiveness of these substances. The aim of this review is to evaluate whether any prebiotic effects, which could help to explain their efficacy or ineffectiveness, are documented in the recent literature for the main nutraceuticals and herbal food supplements used for weight loss management. Several prebiotic effects have been reported for various nutraceutical substances, which have shown activity on Bifidobacterium spp., Lactobacillus spp., Akkermansia muciniphila, Faecalibacterium prausnitzi, Roseburia spp., and the Firmicutes/Bacteroidetes ratio. Different prebiotics have beneficial effects on weight and the related metabolic profile, in some cases even acting on the microbiota with mechanisms that are completely independent from those nutraceuticals for which certain products are normally used. Further studies are necessary to clarify the different levels at which a nutraceutical substance can exert its action.

Similarities and differences of oligo/poly-saccharides' impact on human fecal microbiota identified by in vitro fermentation

The dietary supplementation of prebiotics is considered a promising strategy for the modulation of gut microbiota. Due to the wide variety of animal models and tremendous inter-individual variability from human investigations, the prebiotic effect of fibers is often difficult to compare between studies. Here, the effects of 11 dietary fibers on human fecal microbiota were studied using an in vitro human fecal fermentation model under well-controlled conditions. All fibers showed positive regulatory effects on short chain fatty acids (SCFAs) and several beneficial bacteria, including Parabacteroides distasonis and Bifidobacterium spp. Cultures supplemented with xylo-oligosaccharide and konjac flour showed the highest SCFAs. According to regulatory effects, fibers were divided into three groups, with 13 indicator OTUs (operational taxonomic units) identified. Fecal microbiota regulated by isomalto-oligosaccharide and chitosan-oligosaccharide were similar to fructo-oligosaccharide and inulin outputs. As a supplement to in vivo studies, our results comprehensively summarized the similarities and distinctiveness of fibers in regulating fecal microbiota structures. KEY POINTS: • Fibers were divided into three groups based on the regulatory effects in microbiota. • Thirteen indicator OTUs were identified using pairwise comparisons. • Fiber similarities and distinctive traits in regulating microbiota effect were identified.

Polymer-Based Carriers in Dental Local Healing-Review and Future Challenges

Polymers in drug formulation technology and the engineering of biomaterials for the treatment of oral diseases constitute a group of excipients that often possess additional properties in addition to their primary function, i.e., biological activity, sensitivity to stimuli, mucoadhesive properties, improved penetration of the active pharmaceutical ingredient (API) across biological barriers, and effects on wound healing or gingival and bone tissue regeneration. Through the use of multifunctional polymers, it has become possible to design carriers and materials tailored to the specific conditions and site of application, to deliver the active substance directly to the affected tissue, including intra-periodontal pocket delivery, and to release the active substance in a timed manner, allowing for the improvement of the form of application and further development of therapeutic strategies. The scope of this review is polymeric drug carriers and materials developed from selected multifunctional groups of natural, semi-synthetic, and synthetic polymers for topical therapeutic applications. Moreover, the characteristics of the topical application and the needs for the properties of carriers for topical administration of an active substance in the treatment of oral diseases are presented to more understand the difficulties associated with the design of optimal active substance carriers and materials for the treatment of lesions located in the oral cavity.

Advances in the preparation and assessment of the biological activities of chitosan oligosaccharides with different structural characteristics

Chitosan oligosaccharides (COSs) are widely used biopolymers that have been studied in relation to a variety of abnormal biological activities in the food and biomedical fields. Since different COS preparation technologies produce COS compounds with different structural characteristics, it has not yet been possible to determine whether one or more chito-oligomers are primarily responsible for the bioactivity of COSs. The inherent biocompatibility, mucosal adhesion and nontoxic nature of COSs are well documented, as is the fact that they are readily absorbed from the intestinal tract, but their structure-activity relationship requires further investigation. This review summarizes the methods used for COS preparation, and the research findings with regard to the antioxidant, anti-inflammatory, anti-obesity, bacteriostatic and antitumour activity of COSs with different structural characteristics. The correlation between the molecular structure and bioactivities of COSs is described, and new insights into their structure-activity relationship are provided.

Chitin and Chitosan Derivatives as Biomaterial Resources for Biological and Biomedical Applications

Chitin is a long-chain polymer of N-acetyl-glucosamine, which is regularly found in the exoskeleton of arthropods including insects, shellfish and the cell wall of fungi. It has been known that chitin can be used for biological and biomedical applications, especially as a biomaterial for tissue repairing, encapsulating drug for drug delivery. However, chitin has been postulated as an inducer of proinflammatory cytokines and certain diseases including asthma. Likewise, chitosan, a long-chain polymer of N-acetyl-glucosamine and d-glucosamine derived from chitin deacetylation, and chitosan oligosaccharide, a short chain polymer, have been known for their potential therapeutic effects, including anti-inflammatory, antioxidant, antidiarrheal, and anti-Alzheimer effects. This review summarizes potential utilization and limitation of chitin, chitosan and chitosan oligosaccharide in a variety of diseases. Furthermore, future direction of research and development of chitin, chitosan, and chitosan oligosaccharide for biomedical applications is discussed.

In Vitro Studies Toward the Use of Chitin as Nutraceutical: Impact on the Intestinal Epithelium, Macrophages, and Microbiota

SCOPE

Chitin, the most abundant polysaccharide found in nature after cellulose, is known for its ability to support wound healing and to lower plasma-oxidized low-density lipoprotein (LDL) levels. Studies have also revealed immunomodulatory potential but contradicting results are often impossible to coalesce through usage of chitin of different or unknown physicochemical consistency. In addition, only a limited set of cellular models have been used to test the bioactivity of chitin.

METHODS AND RESULTS

Chitin is investigated with well-defined physicochemical consistency for its immunomodulatory potency using THP-1 macrophages, impact on intestinal epithelial barrier using Caco-2 cells, and fermentation by fecal-derived microbiota. Results show that chitin with a degree of acetylation (DA) of ≈83%, regardless of size, does not affect the intestinal epithelial barrier integrity. Large-sized chitin significantly increases acetic acid production by gut microbiota without altering the composition. Exposure of small-sized chitin to THP-1 macrophages lead to significantly increased secretion of IL-1β, IL-8, IL-10, and CXCL10 in a multi-receptor and clathrin-mediated endocytosis dependent manner.

CONCLUSIONS

These findings indicate that small-sized chitin does not harm the intestinal barrier nor affects SCFA secretion and microbiota composition, but does impact immune activity which could be beneficial to subjects in need of immune support or activation.

Animal-Origin Prebiotics Based on Chitin: An Alternative for the Future? A Critical Review

The human gut microbiota has been revealed in recent years as a factor that plays a decisive role in the maintenance of human health, as well as in the development of many non-communicable diseases. This microbiota can be modulated by various dietary factors, among which complex carbohydrates have a great influence. Although most complex carbohydrates included in the human diet come from vegetables, there are also options to include complex carbohydrates from non-vegetable sources, such as chitin and its derivatives. Chitin, and its derivatives such as chitosan can be obtained from non-vegetable sources, the best being insects, crustacean exoskeletons and fungi. The present review offers a broad perspective of the current knowledge surrounding the impacts of chitin and its derived polysaccharides on the human gut microbiota and the profound need for more in-depth investigations into this topic. Overall, the effects of whole insects or meal on the gut microbiota have contradictory results, possibly due to their high protein content. Better results are obtained for the case of chitin derivatives, regarding both metabolic effects and effects on the gut microbiota composition.

Effect of chitooligosaccharides on human gut microbiota and antiglycation

Chitooligosaccharides (COS) have garnered great attention in the field of human healthcare. The prebiotic activities and antiglycation of COS were investigated using a combination of in vitro and in vivo studies. COS supplementation dramatically increased the levels of acetic acid, while reducing the concentrations of propionic and butyric acids. It also decreased the total bacterial population; however, it did not affect diversity and richness of the gut microbiota. In addition, COS modulated the gut microbiota composition by increasing Bacteroidetes, decreasing Proteobacteria and Actinobacteria, and lowering the Firmicutes/Bacteroidetes ratio. COS promoted the generation of beneficial Bacteroides and Faecalibacterium genera, while suppressing the pathogenic Klebsiella genus. The antiglycation activity of COS and acetic acid was dose-dependent. Furthermore, COS prevented the decrease of serum N^ε-(carboxymethyl) lysine (CML) level caused by CML ingestion in a mouse model of diet-induced obesity. To improve host health, COS could be potential prebiotics in food products.

Nondigestible Oligosaccharides with Anti-Obesity Effects

Obesity has an important influence on health conditions, causing a multitude of complications and comorbidities, and drug therapy is considered to be one of the treatment strategies. Nowadays, there is increasing interest in the study of intestinal microbiota regulation of obesity; also, an increasing number of agricultural and sideline products have been found to have anti-obesity potential. In the present review, we summarize an overview of current known and potential anti-obesity oligosaccharides and their molecular structures. We describe their anti-obesity potential activity and the molecular structure associated with this activity, the regulation of intestinal microbiota composition and its mechanism of action, including regulation of the short-chain fatty acid (SCFA) pathway and altering bile acid (BA) pathway. This review will provide new ideas for us to develop new anti-obesity functional foods.

The triple-wavelength overlapping resonance Rayleigh scattering method and the fluorescence quenching method for the determination of chitooligosaccharides using trisodium-8-hydroxypyrene-1,3,6-trisulfonate as a probe

In this assay, the triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method and the fluorescence quenching method for the quantitative detection of chitooligosaccharides (COS) were developed. In the weakly Britton-Robinson buffer solution, COS interacted with Trisodium-8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to form an ion-association complex of HPTS-COS, which increased the RRS intensities at 321 nm, 430 nm and 511 nm and decreased the fluorescence intensities of the system at 512 nm. And the changes in the intensities of both methods were related to the changes in the concentration of COS. Moreover, for the TWO-RRS method, OP-10 made the RRS intensities increased stronger, finally, the three peaks' total was linear to the concentration of COS in the range of 1.00-8.00 μg/mL and the limit of detection (LOD) was 0.247 μg/mL, and for the fluorescence quenching method, the linear range was 0.50-3.50 μg/mL with the LOD of 0.108 μg/mL. Based on these, two new and fast spectral methods with high sensitivity and simplicity for the determination of trace COS had been established. The generation mechanism of the TWO-RRS and the fluorescence quenching was studied. At the same time, the two methods were applied to the determination of COS in health products with satisfactory results.

Carboxymethyl chitosan perturbs inflammation profile and colonic microbiota balance in mice

Carboxymethyl chitosan (CMC) is widely used in food and medicine as a biodegradable polymer. However, its effects on inflammation profile and colon health are not well investigated. In the present study, CMC was given to mice to evaluate its possible effects on body weight, blood glucose level, inflammation factors, intestinal permeability and colon microbiota. Results showed that blood glucose level of CMC treated mice was relatively higher than control ones. Glucose tolerance test revealed that CMC treated mice presented higher peak glucose level and lower lag level. CMC treatment increased serum LDL-c level, decreased serum HDL-c and IL-10 level in the fat tissue. Moreover, CMC treatment downregulated the expression of tight junction protein, occludin and ZO-1, in colon as evaluated by Western blot. Colon microbiota analysis demonstrated that CMC treatment significantly decreased the OTUs and relative species abundance. The level of Enterobacteriaceae, Lachnospiraceae and several other bacteria were much higher in the colon content of CMC treated mice. The results collectively suggest that CMC treatment induces disturbance of glucose and fat metabolism, affects the inflammation profile, perturbs colon microbiota balance.

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.

Nondigestible carbohydrates, butyrate, and butyrate-producing bacteria

Nondigestible carbohydrates (NDCs) are fermentation substrates in the colon after escaping digestion in the upper gastrointestinal tract. Among NDCs, resistant starch is not hydrolyzed by pancreatic amylases but can be degraded by enzymes produced by large intestinal bacteria, including clostridia, bacteroides, and bifidobacteria. Nonstarch polysaccharides, such as pectin, guar gum, alginate, arabinoxylan, and inulin fructans, and nondigestible oligosaccharides and their derivatives, can also be fermented by beneficial bacteria in the large intestine. Butyrate is one of the most important metabolites produced through gastrointestinal microbial fermentation and functions as a major energy source for colonocytes by directly affecting the growth and differentiation of colonocytes. Moreover, butyrate has various physiological effects, including enhancement of intestinal barrier function and mucosal immunity. In this review, several representative NDCs are introduced, and their chemical components, structures, and physiological functions, including promotion of the proliferation of butyrate-producing bacteria and enhancement of butyrate production, are discussed. We also describe the strategies for achieving directional accumulation of colonic butyrate based on endogenous generation mechanisms.

Exploring Effects of Chitosan Oligosaccharides on Mice Gut Microbiota in in vitro Fermentation and Animal Model

Chitosan oligosaccharides (COS) have shown positive effects on host gut health and influence on intestinal microbial community. However, the bioactivity and mechanism of COS on gut microbiota is still poorly understood. Here, we presented systematic studies of COS on mice fecal/gut microbiota. During in vitro fermentation of COS by mice gut microbiota, total bacterial population significantly decreased after 8-h COS treatment but was returned to the normal level after extended incubation. Consumption of COS and production of SCFAs suggested that COS were utilized by the microbe, although the consumption of chitosan pentasaccharides was obviously slower than others. COS treatments on mice fecal samples caused the decrease of potential pathogenic genera Escherichia/Shigella and the increase of genus Parabacteroides. In vivo animal study indicated that COS reduced population of probiotic genera Lactobacillus, Bifidobacterium and harmful genus Desulfovibrio, and increased abundance of genus Akkermansia. Phylum Proteobacteria was significantly inhibited by COS both in the animal model and in vitro fermentation. Our findings suggested that COS could reform the community structure of gut microbiota. The relationship among COS, gut microbiota and host health deserve further study.

Marine chitinolytic enzymes, a biotechnological treasure hidden in the ocean?

Chitinolytic enzymes are capable to catalyze the chitin hydrolysis. Due to their biomedical and biotechnological applications, nowadays chitinolytic enzymes have attracted worldwide attention. Chitinolytic enzymes have provided numerous useful materials in many different industries, such as food, pharmaceutical, cosmetic, or biomedical industry. Marine enzymes are commonly employed in industry because they display better operational properties than animal, plant, or bacterial homologs. In this mini-review, we want to describe marine chitinolytic enzymes as versatile enzymes in different biotechnological fields. In this regard, interesting comments about their biological role, reaction mechanism, production, functional characterization, immobilization, and biotechnological application are shown in this work.

Chitosan oligosaccharides improve the disturbance in glucose metabolism and reverse the dysbiosis of gut microbiota in diabetic mice

The aim of this study is to investigate the effect of chitosan oligosaccharides (COS) on type 2 diabetes mellitus. Wild type C57BL/6J mice or diabetic db/db mice were treated with vehicle or COS for three months. COS treatment significantly decreased the blood glucose (P < 0.01) and reversed the insulin resistance (P < 0.05) in db/db mice, which was accompanied by suppressing the inflammation mediators (P < 0.05), down-regulating the lipogenesis (P < 0.01) and inhibiting the adipocyte differentiation (P < 0.05) in white adipose tissue. Additionally, COS treatment inhibited the reduction of occludin (P < 0.01) and relieved the gut dysbiosis in diabetic mice by promoting Akkermansia (P < 0.01) and suppressing Helicobacter (P < 0.05). Spearman's correlation analysis indicates that the COS-modulated bacteria are positively correlated with inflammation, hyperglycemia and dyslipidemia. The functional profiling based on the microbiota composition implicated that COS treatment may regulate the metabolic pathways of gut microbiota. In summary, COS treatment remarkably improved the glucose metabolism and reshaped the unbalanced gut microbiota of diabetic mice. Our study provided the evidence for application of COS to the treatment of diabetes mellitus.

Chitin Oligosaccharide Modulates Gut Microbiota and Attenuates High-Fat-Diet-Induced Metabolic Syndrome in Mice

Gut microbiota has been proved to be an indispensable link between nutrient excess and metabolic syndrome, and chitin oligosaccharide (NACOS) has displayed therapeutic effects on multiple diseases such as cancer and gastritis. In this study, we aim to confirm whether NACOS can ameliorate high-fat diet (HFD)-induced metabolic syndrome by rebuilding the structure of the gut microbiota community. Male C57BL/6J mice fed with HFD were treated with NACOS (1 mg/mL) in drinking water for five months. The results indicate that NACOS improved glucose metabolic disorder in HFD-fed mice and suppressed mRNA expression of the protein regulators related to lipogenesis, gluconeogenesis, adipocyte differentiation, and inflammation in adipose tissues. Additionally, NACOS inhibited the destruction of the gut barrier in HFD-treated mice. Furthermore, 16S ribosome RNA sequencing of fecal samples demonstrates that NACOS promoted the growth of beneficial intestinal bacteria remarkably and decreased the abundance of inflammogenic taxa. In summary, NACOS partly rebuilt the microbial community and improved the metabolic syndrome of HFD-fed mice. These data confirm the preventive effects of NACOS on nutrient excess-related metabolic diseases.