Simulated digestion and fermentation in vitro by human gut microbiota of polysaccharides from Helicteres angustifolia L

In vitro simulated digestion and fermentation characteristics of pectic polysaccharides from fresh passion fruit (Passiflora edulis f. flavicarpa L.) peel

In this study, two pectic polysaccharides (PFP-T and PFP-UM) were extracted from fresh passion fruit peels using three-phase partitioning (TPP) and sequential ultrasound-microwave-assisted TPP methods, respectively, and their effects on the in vitro gastrointestinal digestion and fecal fermentation characteristics were examined. The results indicate that gastrointestinal digestion has a minimal effect on the physicochemical and structural characteristics of PFP-T and PFP-UM. However, during in vitro fecal fermentation, both undigested PFP-T and PFP-UM are significantly degraded and utilized by intestinal microorganisms, showing increased the total relative abundance of Firmicutes and Bacteroidota in the intestinal flora. Notably, compared with PFP-UM, PFP-T better promoted the reproduction of beneficial bacteria such as Prevotella, Megasphaera and Dialister, while suppressed the growth of harmful genera including Escherichia-Shigella, producing higher content of short-chain fatty acids. Therefore, our findings suggest that PFP-T derived from passion fruit peel has potential as a dietary supplement for promoting intestinal health.

Multivariate comparison of taxonomic, chemical and operational data from 80 different full-scale anaerobic digester-related systems

BACKGROUND

The holistic characterization of different microbiomes in anaerobic digestion (AD) systems can contribute to a better understanding of these systems and provide starting points for bioengineering. The present study investigates the microbiome of 80 European full-scale AD systems. Operational, chemical and taxonomic data were thoroughly collected, analysed and correlated to identify the main drivers of AD processes.

RESULTS

The present study describes chemical and operational parameters for a broad spectrum of different AD systems. With this data, Spearman correlation and differential abundance analyses were applied to narrow down the role of the individual microorganisms detected. The authors succeeded in further limiting the number of microorganisms in the core microbiome for a broad range of AD systems. Based on 16S rRNA gene amplicon sequencing, MBA03, Proteiniphilum, a member of the family Dethiobacteraceae, the genus Caldicoprobacter and the methanogen Methanosarcina were the most prevalent and abundant organisms identified in all digesters analysed. High ratios for Methanoculleus are often described for agricultural co-digesters. Therefore, it is remarkable that Methanosarcina was surprisingly high in several digesters reaching ratios up to 47.2%. The various statistical analyses revealed that the microorganisms grouped according to different patterns. A purely taxonomic correlation enabled a distinction between an acetoclastic cluster and a hydrogenotrophic one. However, in the multivariate analysis with chemical parameters, the main clusters corresponded to hydrolytic and acidogenic microorganisms, with SAOB bacteria being particularly important in the second group. Including operational parameters resulted in digester-type specific grouping of microbes. Those with separate acidification stood out among the many reactor types due to their unexpected behaviour. Despite maximizing the organic loading rate in the hydrolytic pretreatments, these stages turned into extremely robust methane production units.

CONCLUSIONS

From 80 different AD systems, one of the most holistic data sets is provided. A very distinct formation of microbial clusters was discovered, depending on whether taxonomic, chemical or operational parameters were combined. The microorganisms in the individual clusters were strongly dependent on the respective reference parameters.

In vivo absorption, in vitro simulated digestion and fecal fermentation properties of polysaccharides from Pinelliae Rhizoma Praeparatum Cum Alumine and their effects on human gut microbiota

Polysaccharides from Pinelliae Rhizoma Praeparatum Cum Alumine (PPA) have various biological activities, but their properties after oral administration are not clear. In this study, the absorption, digestion and fermentation properties of PPA were studied using in vivo fluorescence tracking, in vitro simulated digestion and fecal fermentation experiments. The absorption experiment showed that fluorescence was only observed in the gastrointestinal system, indicating that PPA could not be absorbed. Simulated digestion results showed that there were no significant changes in the molecular weight, Fourier transform infrared spectroscopy (FT-IR) spectrum, monosaccharides and reducing sugar of PPA during the digestion process, showing that the overall structure of PPA was not damaged. However, the carbohydrate gel electrophoresis bands of PPA enzymatic hydrolysates after simulated digestion were significantly changed, indicating that simulated digestion might impact the configuration of PPA. In vitro fermentation showed that PPA could be degraded by microorganisms to produce short chain fatty acids, leading to a decrease in pH value. PPA can promote the proliferation of Bacteroideaceae, Megasphaera, Bacteroideaceae, and Bifidobacteriaceae, and inhibit the growth of Desulfobacteriota and Enterobacteriaceae. The results indicated that PPA could treat diseases by regulating gut microbiota, providing a scientific basis for the application and development of PPA.

Interactions between intestinal microbial fermentation products of Pleurotus eryngii polysaccharide with gut mucus

Recently, Pleurotus eryngii (P. eryngii) polysaccharide (PEP) has received a lot of attention from many researchers as the primary active substance. The PEP influences the gut microbiota in several ways, including the interaction of fermentation products with the intestinal mucus layer (IML) and intestinal epithelial cells. Herein, we characterized interactions between the IML and PEP after degradation by the gut microbes. Our results showed that fermented P. eryngii polysaccharide (FPEP) can interact with intestinal mucus (IM), and this interaction can reduce the degree of molecular aggregation of polysaccharides. At the same time, the fermentation time of FPEP also affects the interaction between the two. SEM showed that the FPEP solution tended to aggregate into larger particles, while with the addition of IM, the FPEP molecules were dispersed. Particle size measurements unveil substantial differences in the fermented polysaccharides' particle size between the group with supplementary IM (0 hours of fermentation: 485.1 ± 11.3 nm) and the group without IM (0 hours of fermentation: 989.33 ± 21.3 nm). Remarkably, within the group with added IM, the particle size reached its maximum at 24 hours of fermentation (585.87 ± 42.83 nm). Additionally, turbidity assessments demonstrate that, during the 12-hour interaction period, the 24-hour fermented polysaccharides consistently exhibit the highest OD values, ranging between 0.57 and 0.61. This work investigates the interaction between FPEP and IM, predicting the adhesion of polysaccharides to IM. Meanwhile, this provides a theoretical basis for further studies on the absorption and transport pathways of PEP and provides a novel research viewpoint on intestinal digestion and absorption.

Molecular Mechanism of Polysaccharides Extracted from Chinese Medicine Targeting Gut Microbiota for Promoting Health

The accumulating evidence revealed that gut microbiota plays an important role in pathological process of disease including obesity, type 2 diabetes mellitus, heart failure, and non-alcoholic fatty liver disease. Polysaccharides extracted from Chinese medicine (CM) can not only alleviate pathological status but also promote health by anti-inflammatory, regulating immunity, lowering blood glucose and lipids, anti-cancer, and anti-oxidation. The alterations of gut microbiota composition and metabolism pathways are the potential mechanisms of CM polysaccharides treatment. In addition, they exert functions through gut-organ axis or play an indirect role by synergistic actions with other drugs or components mediated by gut microbiota. This review summarizes the molecular mechanisms of CM polysaccharides interacted with intestinal microbial inhabitants as potential prebiotics for promoting health.

Effect of in vitro digestion and fermentation of kiwifruit pomace polysaccharides on structural characteristics and human gut microbiota

Kiwifruit pomace is abundant in polysaccharides that exhibit diverse biological activities and prebiotic potential. This study delves into the digestive behavior and fermentation characteristics of kiwifruit pomace polysaccharides (KFP) through an in vitro simulated saliva-gastrointestinal digestion and fecal fermentation. The results reveal that following simulated digestion of KFP, its molecular weight reduced by 4.7%, and the reducing sugar (CR) increased by 9.5%. However, the monosaccharide composition and Fourier transform infrared spectroscopy characteristics showed no significant changes, suggesting that KFP remained undigested. Furthermore, even after saliva-gastrointestinal digestion, KFP retained in vitro hypolipidemic and hypoglycemic activities. Subsequently, fecal fermentation significantly altered the physicochemical properties of indigestible KFP (KFPI), particularly leading to an 89.71% reduction in CR. This indicates that gut microbiota could decompose KFPI and metabolize it into SCFAs. Moreover, after 48 h of KFPI fecal fermentation, it was observed that KFPI contributed to maintaining the balance of gut microbiota by promoting the proliferation of beneficial bacteria like Bacteroides, Lactobacillus, and Bifidobacterium, while inhibiting the unfavorable bacteria like Bilophila. In summary, this study offers a comprehensive exploration of in vitro digestion and fecal fermentation characteristics of KFP, providing valuable insights for potential development of KFP as a prebiotic for promoting intestinal health.

Recent advances in the influences of drying technologies on physicochemical properties and biological activities of plant polysaccharides

Plant polysaccharides, as significant functional macromolecules with diverse biological properties, are currently receiving increasing attention. Drying technologies play a pivotal role in the research, development, and application of various foods and plant polysaccharides. The chemical composition, structure, and function of extracted polysaccharides are significantly influenced by different drying technologies (e.g., microwave, infrared, and radio frequency) and conditions (e.g., temperature). This study discusses and compares the principles, advantages, disadvantages, and effects of different drying processes on the chemical composition as well as structural and biological properties of plant polysaccharides. In most plant-based raw materials, molecular degradation, molecular aggregation phenomena along with intermolecular interactions occurring within cell wall components and cell contents during drying represent primary mechanisms leading to variations in chemical composition and structures of polysaccharides. These differences further impact their biological properties. The biological properties of polysaccharides are determined by a combination of multiple relevant factors rather than a single factor alone. This review not only provides insights into selecting appropriate drying processes to obtaining highly bioactive plant polysaccharides but also offers a fundamental theoretical basis for the structure-function relationship of these compounds.

Catabolism of Dictyophora indusiata Polysaccharide and Its Impacts on Gut Microbial Composition during In Vitro Digestion and Microbial Fermentation

Dictyophora indusiata is one of the most famous edible mushrooms in China. D. indusiata polysaccharide (DP) has attracted increasing attention because of its multiple beneficial effects. In this study, the in vitro simulated digestion and microbial fermentation were designed to reveal the potential catabolic property of DP and its impacts on the modulation of gut microbial composition. The results showed that the reducing sugar content, total polysaccharides content, molecular weight, and rheological property of DP were not significantly altered under in vitro simulated digestive conditions. However, the molecular weight, apparent viscosity, and total polysaccharides content of indigestible DP (DPI) significantly decreased during in vitro fecal fermentation, and the reducing sugar content and the release of free monosaccharides notably increased, suggesting that DP could be degraded and used by gut microbiota. Additionally, the relative abundances of several beneficial bacteria, such as Bacteroides, Catenibacterium, Parabacteroides, and Megamonas, increased significantly, indicating that DP can regulate the composition and abundance of gut microbiota. Moreover, DP could also promote the production of SCFAs, thus changing the acid-base environment of the large intestine. The results of this study are beneficial for deeply clarifying the catabolic behavior of DP in the gastrointestinal tract, which can provide a theoretical basis for developing microbiota-directed products based on DP.

Effects of in vitro simulated digestion and fecal fermentation of polysaccharides from straw mushroom (Volvariella volvacea) on its physicochemical properties and human gut microbiota

Herein, the fermentation and digestion behavior of Volvariella volvacea polysaccharide (VVP) were examined through the in vitro simulation experiment. The results revealed that succeeding the simulated salivary gastrointestinal digestion, the molecular weight of VVP was reduced by only 8.9 %. In addition, the reducing sugar, uronic acid, monosaccharide composition and Fourier transform infrared spectroscopy characteristics of VVP did not change significantly, which indicate that saliva-gastrointestinal could not digest VVP. However, 48 h of fecal fermentation of VVP dramatically reduced its molecular weight by 40.4 %. Furthermore, the molar ratios of the monosaccharide composition altered considerably due to the degradation of VVP by microorganisms and the metabolysis into different short-chain fatty acids (SCFAs). Meanwhile, the VVP also raised the proportion of Bacteroidetes to Firmicutes and promoted the proliferation of some beneficial bacteria including Bacteroides and Phascolarctobacterium, whereas it inhibited the growth of unfavorable bacteria such as Escherichia-shigella. Therefore, VVP has the potential to have a positive influence on health and hinder diseases by improving the intestinal microbial environment. These findings provide a theoretical foundation to further develop Volvariella volvacea as a healthy functional food.

In vitro digestion and human gut microbiota fermentation of Bletilla striata polysaccharides and oligosaccharides

Background

Bletilla striata is one of the commonly used traditional Chinese medicine. B. striata polysaccharides (BP) and oligosaccharides (BO) are one of the main components of B. striata, which have been proved to have a variety of biological activities. However, the digestion and fermentation characteristics of BP and BO are still unclear.

Methods

The study evaluated different prebiotic effects of BP and BO by in vitro simulating digestion and gut microbiota fermentation.

Results

The results show that the simulating saliva partly degraded BP, but had no effect on BO. The molecular weights of BP and BO remained basically unchanged in gastric and intestinal digestion. In addition, BP and BO could be rapidly degraded and utilized by gut microbiota. During in vitro fermentation, the growth rates of the BP and BO groups were higher than that of the Control group and the pH value and total carbohydrate content in BP group and BO group decreased significantly. Although the reducing sugar level in the BO group decreased rapidly, it remained at a low level in the BP group. Both BP and BO improved the composition and structure of gut microbiota, indicative of the upregulated abundances of Streptococcus and Veillonella, and the downregulated populations of Escherichia and Bacteroides. There were differences in the SCFA production by gut microbiota and antioxidant activities between the BP and BO groups. The fermentation broth of the BP group displayed a stronger suppression of O₂-, but a higher scavenging effect on DPPH for the BO group.

Conclusions

BP and BO displayed different digestion and fermentation characteristics in vitro due to their distinct polymerization degrees. The study point towards the potential of BP and BO as prebiotics in the application to human diseases by selectively regulating gut microbiota in the future.

In vitro simulated digestion of and microbial characteristics in colonic fermentation of polysaccharides from four varieties of Tibetan tea

Polysaccharides as a functional prebiotic have numerous activities such as regulating intestinal microorganisms and polysaccharide is one of the functional active components in tea has been known. In this study, we aimed to investigate the physicochemical characteristics of polysaccharides from four kinds of Tibetan teas at simulated digestion stages and the effect on the microbiota of fecal fermentation stages in vitro. The results revealed that Tibetan tea polysaccharides were partially digested during digestion. Additionally, during in vitro fecal microbial fermentation, Tibetan tea polysaccharides can promote the growth of some beneficial bacteria such as Bifidobacterium, Prevotella and Phascolarctobacterium to change the composition of intestinal microorganisms and promote the production of short-chain fatty acids (SCFAs). Finally, a strong correlation was found between the production of SCFAs and microorganisms including Bacteroides, Bifidobacterium and Lachnoclostridium. These results suggest that Tibetan tea polysaccharides could be developed as a prebiotic to regulate human gut microbiota.

In vitro digestion and fecal fermentation of Siraitia grosvenorii polysaccharide and its impact on human gut microbiota

In this study, the structure of Siraitia grosvenorii polysaccharides (SGPs) changed significantly after digestion. After 48 h of in vitro fecal fermentation, M_w decreased and the content of C_R showed a trend of increasing and then decreasing. The monosaccharide composition (glucose) of SGPs showed a trend of decreasing and then stabilizing during fecal fermentation, indicating that SGPs were partially degraded during in vitro fermentation and significantly degraded and utilized by the human intestinal microbiota. In addition, SGPs fermentation for 48 h increased the production of SCFAs especially acetic acid, propionic acid, and butyric acid. Moreover, after in vitro digestion and enzymatic digestion, the in vitro hypoglycemic activity of SGPs remained relatively high afterward, albeit reduced. This study contributes to a better understanding of the potential digestion and enzymatic mechanisms of SGP, which is important for the future development of SGP as a functional food and drug.

In vitro simulated digestion affecting physicochemical characteristics and bioactivities of polysaccharides from barley (Hordeum vulgare L.) grasses at different growth stages

In this study, three polysaccharides (BGPs: BGPs-Z21, BGPs-Z23, and BGPs-Z31) were successively extracted from barley (Hordeum vulgare L.) grasses (BG) at different growth stages, including seedling (Z21), tillering (Z23), and stem elongation (Z31). The effects of in vitro simulated saliva-gastrointestinal digestion on the physicochemical characteristics and biological activities of BGPs were investigated and compared. Results showed that the simulated saliva-gastrointestinal digestion had considerable influences on reducing sugar content, chemical components, monosaccharide constituents, and molecular weights of BGPs but hardly affected their preliminarily structural characteristics. Moreover, the antioxidant activities of BGPs were weakened after the simulated saliva-gastrointestinal digestion, but their bile acid-binding capacities were remarkably enhanced. The digested BGPs-Z31 by gastric juice possessed better antioxidant benefit, and bile acid-binding capacity (80.33 %) than other digested products. Overall, these results indicated that BGPs obtained from BG are valuable for functional foods as promising bioactive ingredients.

Digestive Characteristics of Hericium erinaceus Polysaccharides and Their Positive Effects on Fecal Microbiota of Male and Female Volunteers During in vitro Fermentation

Hericium erinaceus polysaccharides (HEPs) have attracted widespread attention in regulating gut microbiota (GM). To investigate digestibility and fermentation of HEPs and their effects on GM composition, three polysaccharide fractions, namely, HEP-30, HEP-50, and HEP-70, were fractionally precipitated with 30%, 50%, and 70% ethanol concentrations (v/v) from hot water-soluble extracts of Hericium erinaceus, respectively. Three kinds of prepared HEPs were structurally characterized and simulated gastrointestinal digestion, and their effects on human fecal microbiota fermentations of male and female and short-chain fatty acid (SCFA) production in vitro were clarified. Under digestive conditions simulating saliva, stomach, and small intestine, HEPs were not significantly influenced and safely reached the distal intestine. After 24 h of in vitro fermentation, the content of SCFAs was significantly enhanced (p < 0.05), and the retention rates of total and reducing sugars and pH value were significantly decreased (p < 0.05). Thus, HEPs could be utilized by GM, especially HEP-50, and enhanced the relative abundance of SCFA-producing bacteria, e.g., Bifidobacterium, Faecalibacterium, Blautia, Butyricicoccus, and Lactobacillus. Furthermore, HEPs reduced the relative abundances of opportunistic pathogenic bacteria, e.g., Escherichia-Shigella, Klebsiella, and Enterobacter. This study suggests that gradual ethanol precipitation is available for the preparation of polysaccharides from Hericium erinaceus, and the extracted polysaccharide could be developed as functional foods with great development value.

Metabolic stimulation-elicited transcriptional responses and biosynthesis of acylated triterpenoids precursors in the medicinal plant Helicteres angustifolia

BACKGROUND

Helicteres angustifolia has long been used in Chinese traditional medicine. It has multiple pharmacological benefits, including anti-inflammatory, anti-viral and anti-tumor effects. Its main active chemicals include betulinic acid, oleanolic acid, helicteric acid, helicterilic acid, and other triterpenoid saponins. It is worth noting that some acylated triterpenoids, such as helicteric acid and helicterilic acid, are characteristic components of Helicteres and are relatively rare among other plants. However, reliance on natural plants as the only sources of these is not enough to meet the market requirement. Therefore, the engineering of its metabolic pathway is of high research value for enhancing the production of secondary metabolites. Unfortunately, there are few studies on the biosynthetic pathways of triterpenoids in H. angustifolia, hindering its further investigation.

RESULTS

Here, the RNAs of different groups treated by metabolic stimulation were sequenced with an Illumina high-throughput sequencing platform, resulting in 121 gigabases of data. A total of 424,824 unigenes were obtained after the trimming and assembly of the raw data, and 22,430 unigenes were determined to be differentially expressed. In addition, three oxidosqualene cyclases (OSCs) and four Cytochrome P450 (CYP450s) were screened, of which one OSC (HaOSC1) and one CYP450 (HaCYPi3) achieved functional verification, suggesting that they could catalyze the production of lupeol and oleanolic acid, respectively.

CONCLUSION

In general, the transcriptomic data of H. angustifolia was first reported and analyzed to study functional genes. Three OSCs, four CYP450s and three acyltransferases were screened out as candidate genes to perform further functional verification, which demonstrated that HaOSC1 and HaCYPi3 encode for lupeol synthase and β-amyrin oxidase, which produce corresponding products of lupeol and oleanolic acid, respectively. Their successful identification revealed pivotal steps in the biosynthesis of acylated triterpenoids precursors, which laid a foundation for further study on acylated triterpenoids. Overall, these results shed light on the regulation of acylated triterpenoids biosynthesis.

Lactobacillus plantarum ZJ316 improves the quality of Stachys sieboldii Miq. pickle by inhibiting harmful bacteria growth and degrading nitrite, promoting the gut microbiota health in vitro

Microbial contamination and nitrite accumulation are two major concerns on the quality control of fermented vegetables. In the present study, a lactic acid bacteria strain Lactobacillus plantarum ZJ316 (ZJ316) was...

In vitro digestive characteristics and microbial degradation of polysaccharides from lotus leaves and related effects on the modulation of intestinal microbiota

Polysaccharides exist as one of the most abundant components in lotus leaves, which attract increasing attention owing to their promising health-promoting benefits. In this study, the digestive and microbial degradation characteristics of lotus leaf polysaccharides (LLP) were studied by using an in vitro gastrointestinal model. The results suggested that LLP was stable in the human upper gastrointestinal tract in vitro according to its digestive stabilities at different simulated digestion stages. Conversely, the indigestible LLP (LLPI) could be remarkably utilized by intestinal microbiota in human feces during in vitro fermentation, and its fermentability was 58.11% after the in vitro fermentation of 48 h. Indeed, the microbial degradation characteristics of LLPI during in vitro fermentation by human fecal inoculum were revealed. The results showed that the content of reducing sugars released from LLPI obviously increased from 0.498 to 2.176 mg/mL at the initial fermentation stage (0–6 h), and its molecular weight sharply decreased from 4.08 × 10⁴ to 2.02 × 10⁴ Da. Notably, the molar ratios of arabinose (Ara), galactose (Gal), and galacturonic acid (GalA) in LLPI decreased from 2.89 to 1.40, from 5.46 to 3.72, and from 21.24 to 18.71, respectively, suggesting that the utilization of arabinose and galactose in LLPI by intestinal microbiota was much faster than that of galacturonic acid at the initial fermentation stage. Additionally, LLPI could remarkably regulate gut microbial composition by increasing the abundances of several beneficial microbes, including Bacteroides, Bifidobacterium, Megamonas, and Collinsella, resulting in the promoted generation of several short-chain fatty acids, especially acetic, propionic, and butyric acids. The findings from the present study are beneficial to better understanding the digestive and microbial degradation characteristics of LLP, which indicate that LLP can be used as a potential prebiotic for the improvement of intestinal health.

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LLP was stable in the human upper gastrointestinal tract in vitro.

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The indigestible LLP could be remarkably utilized by intestinal microbiota.

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Arabinose and galactose were quickly utilized at the initial fermentation stage.

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Bacteroides, Bifidobacterium, Megamonas, and Collinsella obviously increased.

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SCFAs, especially acetic, propionic, and butyric acids, remarkably promoted.

Development and evaluation of a novel nanofibersolosome for enhancing the stability, in vitro bioaccessibility, and colonic delivery of cyanidin-3-O-glucoside

The development of colon-specific carrier systems using polysaccharides for oral delivery of nutraceuticals is of great importance for the treatment and/or prevention of inflammatory bowel diseases. In this study, self-assembly with the assistance of vortexing and pulsed-ultrasonication was employed to develop a Fibersol®-2 (a digestion-resistant polysaccharide) and lipoid S75 based novel nanocarrier (denoted as nanofibersolosome) for the colonic delivery of cyanidin-3-O-glucoside (C3G). A series of nanofibersolosome formulations (CFS-0.5-4, 0.5-4 represent the ratios of Fibersol®-2:lipoid S75) were developed and their performance was compared with Fibersol®-2-free reference lipid formulation (CFS-0). The nanofibersolosomes (<150 nm) were spherical and unilamellar with high negative surface charge (-38 to -51 mV) and good encapsulation efficiency (EE > 90%). They performed much better than CFS-0 in retaining their physical properties during freeze drying, preventing particle aggregation, and retaining C3G during storage (4 and 25 ℃) and thermal treatments (40, 60, and 80 ℃). They also exhibited significantly higher stability during simulated gastrointestinal digestion than CFS-0. These desirable features of the nanofibersolosomes (especially CFS-0.5 and CFS-1) led to the efficient delivery of higher concentrations of C3G to the colon than CFS-0. Moreover, gastrointestinal-digested and colonic-fermented nanofibersolosome samples exhibited significantly higher DPPH radical scavenging activity and stronger promoting effect on short-chain fatty acid generation than CFS-0. These in vitro findings indicate that the novel nanofibersolosome possesses great potential for the colonic delivery of C3G and likely other hydrophilic labile phytochemicals that merits further evaluation in in vivo models.

Prebiotic characteristics of arabinogalactans during in vitro fermentation through multi-omics analysis

BACKGROUND AND OBJECTIVES

Dietary fibers have beneficial effects on human health through the interaction with gut microbiota. Larch wood arabinogalactan (LA-AG) is one kind of complex soluble dietary fibers that may be utilized by human gut microbiota.

METHODS AND RESULTS

In this study, the LA-AG degradation by gut microbiota were characterized by investigating the change of LA-AG, microbiota composition, and the production of short-chain fatty acids (SCFAs), lactic acid, succinic acid, as well as volatile organic metabolites. During the fermentation, pH decreased continuously, along with the organic acids (especially acetic acid and lactic acid) accumulating. LA-AG was degraded by gut microbiota then some beneficial metabolites were produced. In addition, LA-AG inhibited the proliferation of some gut microbiota (Unclassified_Enterobacteriaceae and Citrobacter) and the accumulation of some metabolites (Sulfide and indole) released by gut microbiota.

CONCLUSION

LA-AG was partly fermentable fibers with prebiotic potential for human gut health.

Simulated digestion and fecal fermentation behaviors of exopolysaccharides from Paecilomyces cicadae TJJ1213 and its effects on human gut microbiota

This study aimed to explore the in vitro simulated digestion and fecal fermentation behaviors of two purified exopolysaccharide fractions (EPS1 and EPS2) from Paecilomyces cicadae TJJ1213 and its effects on human gut microbiota composition. Results showed that EPS1 and EPS2 could not be digested by saliva-gastrointestinal. After fecal fermentation, however, the molecular weight of EPS1 and EPS2 significantly decreased, and the molar ratios of the monosaccharide composition remarkably changed, indicating that EPS1 and EPS2 could be degraded and consumed by human gut microbiota. Notably, EPS1 and EPS2 could significantly modulate the composition, via increasing the relative abundances of Bacteroides and Phascolarctobacterium and decreasing the pathogenic bacteria Escherichia-Shigella, Klebsiella and Fusobacterium. In addition, EPS1 and EPS2 also could promote the production of short-chain fatty acids during fermentation for 24 h. These results suggest that EPS from Paecilomyces cicadae TJJ1213 can be used as a functional food to improve health and prevent diseases by promoting gut health.

An in vitro batch fermentation protocol for studying the contribution of food to gut microbiota composition and functionality

Knowledge of the effect of foods on gut microbiota composition and functionality is expanding. To isolate the effect of single foods and/or single nutrients (i.e., fiber, polyphenols), this protocol describes an in vitro batch fermentation procedure to be carried out after an in vitro gastrointestinal digestion. Therefore, this is an extension of the previous protocol described by Brodkorb et al. (2019) for studying in vitro digestion. The current protocol uses an oligotrophic fermentation medium with peptone and a high concentration of fecal inoculum from human fecal samples both to provide the microbiota and as the main source of nutrients for the bacteria. This protocol is recommended for screening work to be performed when many food samples are to be studied. It has been used successfully to study gut microbiota fermentation of different foodstuffs, giving insights into their functionality, community structure or ability to degrade particular substances, which can contribute to the development of personalized nutrition strategies. The procedure does not require a specific level of expertise. The protocol takes 4-6 h for preparation of fermentation tubes and 20 h for incubation.

Dietary Fiber Modulates the Fermentation Patterns of Cyanidin-3-O-Glucoside in a Fiber-Type Dependent Manner

The interactions between cell-wall polysaccharides and polyphenols in the gastrointestinal tract have attracted extensive attention. We hypothesized that dietary fiber modulates the fermentation patterns of cyanidin-3-O-glucoside (C3G) in a fiber-type-dependent manner. In the present study, the effects of four dietary fibers (fructose-oligosaccharides, pectin, β-glucan and arabinoxylan) on the modulation of C3G fermentation patterns were investigated through in vitro fermentation inoculated with human feces. The changes in gas volume, pH, total carbohydrate content, metabolites of C3G, antioxidant activity, and microbial community distribution during in vitro fermentation were analyzed. After 24 h of fermentation, the gas volume and total carbohydrate contents of the four dietary-fiber-supplemented groups respectively increased and decreased to varying degrees. The results showed that the C3G metabolites after in vitro fermentation mainly included cyanidin, protocatechuic acid, 2,4,6-trihydroxybenzoic acid, and 2,4,6-trihydroxybenzaldehyde. Supplementation of dietary fibers changed the proportions of C3G metabolites depending on the structures. Dietary fibers increased the production of short-chain fatty acids and the relative abundance of gut microbiota Bifidobacterium and Lactobacillus, thus potentially maintaining colonic health to a certain extent. In conclusion, the used dietary fibers modulate the fermentation patterns of C3G in a fiber-type-dependent manner.

Catechin-grafted arabinoxylan conjugate: Preparation, structural characterization and property investigation

In this study, a high molecular weight arabinoxylan (AX, Mw: 694 kDa) from wheat bran was alkaline extracted and covalently linked with Catechin (CA) by free radical catalytic reaction. Comparing to AX, arabinoxylan-catechin (AX-CA) conjugates demonstrated an extra UV-vis absorption peak at 274 nm, a new FT-IR absorption band at 1516 cm^-1 and new proton signals at 6.5-7.5 ppm, which all confirmed the covalently linked structure. Grafting CA onto AX not only decreased the molecular weight, thermal stability and apparent viscosity of AX, but also enhanced its inhibition effects on starch digestibility in vitro. The in vitro fermentation test with pig feces showed that the degradation & utilization rate of AX, the total short-chain fatty acid (SCFA) and acetic acid levels produced all were significantly delayed after grafting. This study provided a novel approach to synthesize AX-CA conjugates that could be a novel dietary fiber of enhanced functional/bioactive properties using in the fields of functional foods and medicine.

Dynamic changes of structural characteristics of snow chrysanthemum polysaccharides during in vitro digestion and fecal fermentation and related impacts on gut microbiota

The in vitro simulated saliva-gastrointestinal digestion and human fecal fermentation of snow chrysanthemum polysaccharides (JHP) were investigated. Results showed that reducing sugar contents of JHP increased during the gastrointestinal digestion, and glucose released with the decrease of its molecular weight, suggesting that JHP could be partially degraded under the gastrointestinal digestion. Furthermore, after in vitro fecal fermentation, the molecular weight and molar ratio of constituent monosaccharides (galactose and galacturonic acid) of the indigestible JHP (JHP-I) significantly decreased, and both monosaccharides and oligosaccharides released, suggesting that JHP-I could be further degraded and consumed by gut microbiota. Some beneficial bacteria, such as genera Bifidobacterium, Lactobacillus, Megamonas, and Megasphaera, significantly increased, suggesting that JHP-I could change the composition and abundance of gut microbiota. These results suggest that JHP is a potential source of prebiotics, and can be helpful for better understanding of the potential digestion and fermentation mechanism of JHP.

Galactofucan from Laminaria japonica is not degraded by the human digestive system but inhibits pancreatic lipase and modifies the intestinal microbiota

The effects of galactofucan from Laminaria japonica on the digestion and intestinal microbiota of human were investigated in the present study. Crude fraction of the sulfated polysaccharide from L. japonica (CF) and its molecular-weight homogeneous fraction (CGF-3) were prepared and characterized. In the simulated digestion model for the human saliva and gastrointestinal tract, no obvious changes in the molecular weight or the reducing sugar content of CGF-3 were observed, indicating CGF-3 is resistant to the human digestive system. Then CGF-3 did not affect the α-amylase activity while it dose-dependently inhibited the activity of pancreatic lipase partly depending on its sulfate groups. In the in vitro fermentation with the human fecal microbiota, CF did not change the total carbohydrate, reducing sugar and short chain fatty acids contents, which indicated CF was not utilized by the microbiota. However, the microbiota composition was modulated greatly by CF intervention. These findings shed a light on the better understanding of the impacts of dietary galactofucan on the digestion and intestinal microbiota.

In vitro simulated digestion and fecal fermentation of polysaccharides from loquat leaves: Dynamic changes in physicochemical properties and impacts on human gut microbiota

The aim of this study was to well understand the dynamic changes of physicochemical properties of polysaccharides from loquat leaves (LLP) during in vitro simulated saliva-gastrointestinal digestion and fecal fermentation and its related impacts on human gut microbiota. Results showed that the contents of reducing sugar of LLP slightly increased during the gastrointestinal digestion, and its molecular weight also slightly decreased, suggesting that LLP could be slightly degraded under the gastrointestinal digestion conditions. Moreover, during the fecal fermentation, the molecular weight of the indigestible LLP (LLP-I) significantly decreased, and the molar ratio of constituent monosaccharides of LLP-I, such as glucuronic acid, galacturonic acid, galactose, and arabinose, significantly changed, indicating that LLP-I could be degraded and consumed by human gut microbiota. Indeed, some beneficial bacteria such as Megasphaera, Megamonas, Bifidobacterium, Phascolarctobacterium, and Desulfovibrio significantly increased, suggesting that LLP-I could change the composition and abundance of gut microbiota. LLP-I could also promote the production of health-promoting short chain fatty acids. Results from this study are benefical to well understand the in vitro digestion and fecal fermentation behaviors of LLP, and LLP can be developed as a potential prebiotic in the functional food industry.

Polysaccharide from Pleurotus nebrodensis: Physicochemical, structural characterization and in vitro fermentation characteristics

A high Mw (5012 kDa) polysaccharide (PNPS) from the fruiting body of Pleurotus nebrodensis was isolated using water extraction followed by ethanol precipitation. The structural characteristics and in vitro fermentation behaviors of this polysaccharide was investigated. Chemical composition analysis showed the total sugar content of PNPS was up to 97.20 ± 1.80 wt%. Monosaccharide composition analysis showed PNPS contained mainly glucose (89.22 ± 5.70 mol%) while small percentage of mannose (5.60 ± 0.74 mol%) and galactose (5.18 ± 0.33 mol%) were also detected. According to the linkage pattern analysis (methylation analysis), PNPS comprised mainly 4-β-D-Glcp (58.90 mol%), while other residues including α-D-Glcp, 6-α-D-Galp, 3,6-α-D-Manp, 3-β-D-Glcp and 6-α-D-Glcp were detected with a comparable amount. Combined with results from 1D and 2D NMR spectrum, a proposed structure of PNPS was presented. In vitro fermentation of PNPS by gut microbiota showed total SCFA production of all treatment groups was higher than negative control group (NC) significantly (p < 0.05) after 48 h of fermentation. The formation of SCFAs was mainly acetic acid, followed by propionic acid and butyric acid, and the pH was decreased from 6.95 to 4.70. After 72 h, the total sugar content decreased from 5.813 ± 0.87 mg/L to 0.23 ± 0.065 mg/L, and the molecular weight of PNPS decreased.

In vitro fermentation of Gracilaria lemaneiformis sulfated polysaccharides and its agaro-oligosaccharides by human fecal inocula and its impact on microbiota

The fermentation behaviour of sulfated polysaccharides (GLP) and their agaro-oligosaccharides (GLO) derived from Gracilaria lemaneiformis were examined. During in vitro fermentation, GLP and GLO increased the concentrations of short chain fatty acids (SCFAs) and modulated the composition and diversity of gut microorganisms compared with control groups. GLP increased the abundance of Bacteroidetes and decreased the abundance of Firmicutes, while GLO increased the abundance of Firmicutes and Actinobacteria. Moreover, the abundances of potential pathogenic bacteria were reduced. Molecular weight and intrinsic viscosity of GLP decreased significantly from 2.15 × 10⁵ to 1.22 × 10⁵ Da, 374.45-113.91 mL/g, respectively. Furthermore, GLP was degraded into smaller degree of polymerization of oligosaccharides, with no significant change observed in GLO. Overall, this study revealed GLP and GLO could be beneficial for gastrointestinal tract by producing SCFAs and modulating intestinal microbes, indicating GLP and GLO are potentially sources of prebiotics in functional foods.