In vitro digestibility and prebiotic potential of curdlan (1 → 3)-β- d -glucan oligosaccharides in Lactobacillus species

Food carbohydrates in the gut: structural diversity, microbial utilization, and analytical strategies

Carbohydrates, which are a vital dietary component, undergo digestion and gut fermentation through microbial enzymes to produce beneficial short-chain fatty acids. Certain carbohydrates selectively modulate the gut microbiota, impacting host health. Carbohydrate-active enzymes within the gut microbiota significantly contribute to carbohydrate utilization and microbial diversity. Despite their importance, the structural complexity of carbohydrates poses analytical challenges. However, recent advancements, notably, mass spectrometry, have allowed for their characterization and functional analysis. This review examines the intricate relationship between dietary carbohydrates and the gut microbiota, highlighting the crucial role of advanced analytical techniques in understanding their diversity and implications. These advancements provide valuable insights into carbohydrate bioactivity. Integrating high-throughput analysis with next-generation sequencing provides deeper insights into gut microbial interactions, potentially revealing which carbohydrate structures are beneficial for gut health.

Polyphasic identification of Rhizopus oryzae and evaluation of physical fermentation parameters in potato starch processing liquid waste for β-glucan production

Β-glucans are polysaccharide macromolecules that can be found in the cell walls of molds, such as Rhizopus oryzae. They provide functional properties in food systems and have immunomodulatory activity, anticancer, and prebiotic effects; reduce triglycerides and cholesterol; and prevent obesity, among others benefits. Furthermore, potato starch production requires a large amount of water, which is usually discharged into the environment, creating problems in soils and bodies of water. The physical parameters to produce β-glucans were determined, liquid waste from potato starch processing was used and native Rhizopus oryzae was isolated and identified from cereal grains. The isolates grew quickly on the three types of agars used at 25 °C and 37 °C, and they did not grow at 45 °C. Rhizopus oryzae M10A1 produced the greatest amount of β-glucans after six days of culture at 30 °C, pH 6, a stirring rate of 150 rpm and a fermentation volume of 250 mL. By establishing the physical fermentation parameters and utilizing the liquid waste from potato starch, Rhizopus oryzae M10A1 yielded 397.50 mg/100 g of β-glucan was obtained.

In vitro batch fermentation demonstrates variations in the regulation of gut microbiota and metabolic functions by β-glucans of differing structures

The gut microbiota is widely acknowledged as a crucial factor in regulating host health. The structure of dietary fibers determines changes in the gut microbiota and metabolic differences resulting from their fermentation, which in turn affect gut microbe-related health effects. β-Glucan (BG) is a widely accessible dietary fiber to humans, and its structural characteristics vary depending on the source. However, the interactions between different structural BGs and gut microbiota remain unclear. This study used an in vitro fermentation model to investigate the effects of BG on gut microbiota, and microbiomics and metabolomics techniques to explore the relationship between the structure of BG, bacterial communities, and metabolic profiles. The four sources of BG (barley, yeast, algae, and microbial fermentation) contained different types and proportions of glycosidic bonds, which differentially altered the bacterial community. The BG from algal sources, which contained only β(1 → 4) glycosidic bonds, was the least metabolized by the gut microbiota and caused limited metabolic changes. The other three BGs contain more diverse glycosidic bonds and can be degraded by bacteria from multiple genera, causing a wider range of metabolic changes. This work also suggested potential synergistic degradation relationships between gut bacteria based on BG. Overall, this study deepens the structural characterization-microbial-functional understanding of BGs and provides theoretical support for the development of gut microbiota-targeted foods.

Structural and functional analysis of SpGlu64A: a novel glycoside hydrolase family 64 laminaripentaose-producing β-1,3-glucanase from Streptomyces pratensis

Laminaripentaose (L5)-producing β-1,3-glucanases can preferentially cleave the triple-helix curdlan into β-1,3-glucooligosaccharides, especially L5. In this study, a newly identified member of the glycoside hydrolase family 64, β-1,3-glucanase from Streptomyces pratensis (SpGlu64A), was functionally and structurally characterized. SpGlu64A shared highest identity (30%) with a β-1,3-glucanase from Streptomyces matensis. The purified SpGlu64A showed maximal activity at pH 7.5 and 50 °C, and exhibited strict substrate specificity toward curdlan (83.1 U·mg-1). It efficiently hydrolyzed curdlan to produce L5 as the end product. The overall structure of SpGlu64A consisted of a barrel domain and a mixed (α/β) domain, which formed an unusually wide groove with a crescent-like structure. In the two complex structures (SpGlu64A-L3 and SpGlu64A-L4), two oligosaccharide chains were captured and the triple-helical structure was relatively compatible with the wide groove, which suggested the possibility of binding to the triple-helical β-1,3-glucan. A catalytic framework (β6-β9-β10) and the steric hindrance formed by the side chains of residues Y161, N163, and H393 in the catalytic groove were predicted to complete the exotype-like cleavage manner. On the basis of the structure, a fusion protein with the CBM56 domain (SpGlu64A-CBM) and a mutant (Y161F; by site-directed mutation) were obtained, with 1.2- and 1.7-fold increases in specific activity, respectively. Moreover, the combined expression of SpGlu64A-CBM and -Y161F improved the enzyme activity by 2.63-fold. The study will not only be helpful in understanding the reaction mechanism of β-1,3-glucanases but will also provide a basis for further enzyme engineering.

Grafting chlorogenic acid enhanced the antioxidant activity of curdlan oligosaccharides and modulated gut microbiota

In this study, the effects of grafting chlorogenic acid (CA) on the antioxidant and probiotic activities of curdlan oligosaccharides (CDOS) were investigated. CDOS with degrees of polymerization of 3-6 was first obtained by degradation of curdlan with hydrogen peroxide and then grafted with CA using a free radical-mediated method under an ultrasonication-assisted Fenton system. The thermal stability and antioxidant ability of CDOS were enhanced after grafting with CA. In vitro fermentation, supplementation of CDOS-CA stimulated the proliferation of Prevotella and Faecalibacterium while inhibiting the growth of harmful microbiota. Notably, the concentration of total short-chain fatty acids and the relative abundance of beneficial bacteria markedly increased after fermentation of CDOS-CA, indicating that CA grafting could improve the probiotic activity of CDOS. Overall, the covalent binding of CDOS and CA could enhance the antioxidant and probiotic activities of CDOS, suggesting potential improvements in gastrointestinal and colonic health.

Structural insights into curdlan degradation via a glycoside hydrolase containing a disruptive carbohydrate-binding module

BACKGROUND

Degradation via enzymatic processes for the production of valuable β-1,3-glucooligosaccharides (GOS) from curdlan has attracted considerable interest. CBM6E functions as a curdlan-specific β-1,3-endoglucanase, composed of a glycoside hydrolase family 128 (GH128) module and a carbohydrate-binding module (CBM) derived from family CBM6.

RESULTS

Crystallographic analyses were conducted to comprehend the substrate specificity mechanism of CBM6E. This unveiled structures of both apo CBM6E and its GOS-complexed form. The GH128 and CBM6 modules constitute a cohesive unit, binding nine glucoside moieties within the catalytic groove in a singular helical conformation. By extending the substrate-binding groove, we engineered CBM6E variants with heightened hydrolytic activities, generating diverse GOS profiles from curdlan. Molecular docking, followed by mutation validation, unveiled the cooperative recognition of triple-helical β-1,3-glucan by the GH128 and CBM6 modules, along with the identification of a novel sugar-binding residue situated within the CBM6 module. Interestingly, supplementing the CBM6 module into curdlan gel disrupted the gel's network structure, enhancing the hydrolysis of curdlan by specific β-1,3-glucanases.

CONCLUSIONS

This study offers new insights into the recognition mechanism of glycoside hydrolases toward triple-helical β-1,3-glucans, presenting an effective method to enhance endoglucanase activity and manipulate its product profile. Furthermore, it discovered a CBM module capable of disrupting the quaternary structures of curdlan, thereby boosting the hydrolytic activity of curdlan gel when co-incubated with β-1,3-glucanases. These findings hold relevance for developing future enzyme and CBM cocktails useful in GOS production from curdlan degradation.

Effects of In Vitro Fermentation of Polysialic Acid and Sialic Acid on Gut Microbial Community Composition and Metabolites in Healthy Humans

The influence of polysialic acid (PSA) and sialic acid (SA) on the gut microbial community composition and metabolites in healthy humans was investigated using a bionic gastrointestinal reactor. The results indicated that PSA and SA significantly changed the gut microbiota and metabolites to different degrees. PSA can increase the relative abundances of Faecalibacterium and Allisonella, whereas SA can increase those of Bifidobacterium and Megamonas. Both can significantly increase the content of short-chain fatty acids. The results of metabolome analysis showed that PSA can upregulate ergosterol peroxide and gallic acid and downregulate the harmful metabolite N-acetylputrescine. SA can upregulate 4-pyridoxic acid and lipoic acid. PSA and SA affect gut microbiota and metabolites in different ways and have positive effects on human health. These results will provide a reference for the further development of PSA- and SA-related functional foods and health products.

Comprehensive evaluation of the prebiotic properties of Dendrobium officinale polysaccharides, β-glucan, and inulin during in vitro fermentation via multi-omics analysis

Dietary fiber is crucial for human health mainly due to its impact on gut microbiota structure and metabolites. This study aimed to investigate the impact of Dendrobium officinale polysaccharides (DOP) and two common fibers (β-glucan and inulin) on the gut microbiome structure and metabolic profile in vitro. Fecal samples were obtained from 30 healthy volunteers, which were then individually subjected to fermentation with each type of fiber. The results revealed that all fibers were efficiently degraded by gut microbiota, with DOP exhibiting a slower fermentation rate compared to β-glucan and inulin. The fermentation of all fibers led to a significant increase in the production of short-chain fatty acids (SCFAs) and a reduction in branched-chain fatty acids (BCFAs), sulfides, phenols, and indole. Moreover, the abundance of unclassified Enterobacteriaceae, which was positively correlated with sulfide, phenols, and indole levels, was significantly reduced by all fibers. Additionally, DOP specifically promoted the growth of Parabacteroides, while β-glucan and inulin promoted the growth of Bifidobacterium and Faecalibacterium. Taken together, these findings enhance our understanding of the role of DOP, β-glucan, and inulin in modulating gut microbiota and metabolites, where the fermentation with fecal bacteria from different volunteers could provide valuable insights for personalized therapeutic approaches.

Gypsum-Related Impact on Antibiotic-Loaded Composite Based on Highly Porous Hydroxyapatite-Advantages and Disadvantages

Highly porous hydroxyapatite is sometimes considered toxic and useless as a biomaterial for bone tissue regeneration because of the high adsorption of calcium and phosphate ions from cell culture media. This negatively affects the osteoblast's growth in such ion-deprived media and suggests "false cytotoxicity" of tested hydroxyapatite. In our recent study, we showed that a small addition of calcium sulfate dihydrate (CSD) may compensate for this adsorption without a negative effect on other properties of hydroxyapatite-based biomaterials. This study was designed to verify whether such CSD-supplemented biomaterials may serve as antibiotic carriers. FTIR, roughness, mechanical strength analysis, drug release, hemocompatibility, cytotoxicity against human osteoblasts, and antibacterial activity were evaluated to characterize tested biomaterials. The results showed that the addition of 1.75% gypsum and gentamicin caused short-term calcium ion compensation in media incubated with the composite. The combination of both additives also increased antibacterial activity against bacteria representative of bone infections without affecting osteoblast proliferation, hemocompatibility, and mechanical parameters. Thus, gypsum and antibiotic supplementation may provide advanced functionality for bone-regeneration materials based on hydroxyapatite of a high surface area and increasingly high Ca2+ sorption capacity.

Unlocking the benefits of split gill mushroom: Chemical analysis and prebiotic properties of schizophyllan extract

The edible split gill mushroom is considered both a nutritive and therapeutic superfood, as well as rich in schizophyllan and protein. Prebiotic properties and other biological effects distinguish the schizophyllan (β-glucan). Thus, this research investigates the identity of the mushroom strain, the nutritional composition of this mushroom, and the schizophyllan extract for further analysis, including its prebiotic activity and so on. The experimental results revealed that this mushroom was identified as Schizophyllum commune, comprising more excellent carbohydrates, protein, crude fiber, lower fat, and no heavy metal detection. Moreover, this extract consisted of pharmaceutical hydrophobin (14.0-18.5 kDa), lectin protein (21-35 kDa), bioactive purpurin or red pigment, including the prebiotic β-glucan stimulating the proliferation of probiotic bacteria isolated from yogurt. Therefore, both S. commune and the schizophyllan extract can be used as a prebiotic candidate, functional food, and nutraceutical product.

Gut firmicutes: Relationship with dietary fiber and role in host homeostasis

Firmicutes and Bacteroidetes are the predominant bacterial phyla colonizing the healthy human gut. Accumulating evidence suggests that dietary fiber plays a crucial role in host health, yet most studies have focused on how the dietary fiber affects health through gut Bacteroides. More recently, gut Firmicutes have been found to possess many genes responsible for fermenting dietary fiber, and could also interact with the intestinal mucosa and thereby contribute to homeostasis. Consequently, the relationship between dietary fiber and Firmicutes is of interest, as well as the role of Firmicutes in host health. In this review, we summarize the current knowledge regarding the molecular mechanism of dietary fiber degradation by gut Firmicutes and explain the communication pathway of the dietary fiber-Firmicutes-host axis, and the beneficial effects of dietary fiber-induced Firmicutes and their metabolites on health. A better understanding of the dialogue sustained by the dietary fiber-Firmicutes axis and the host could provide new insights into probiotic therapy and novel dietary interventions aimed at increasing the abundance of Firmicutes (such as Faecalibacterium, Lactobacillus, and Roseburia) to promote health.

Antioxidant Activities and Prebiotic Activities of Water-Soluble, Alkali-Soluble Polysaccharides Extracted from the Fruiting Bodies of the Fungus Hericium erinaceus

In this study, the digestion and fermentation properties of the bioactive water-soluble polysaccharide (HEP-W), and alkali-soluble polysaccharide (HEP-A) from Hericium erinaceus and the impact on the human colonic microbiota were determined using simulated saliva-gastrointestinal digestion and human fecal fermentation models in vitro. The basic physicochemical properties of HEP-W and HEP-A were determined at the same time. The results showed that the in vitro simulated digestion had almost no effect on the physicochemical properties of HEP-W and HEP-A, indicating that HEP-W and HEP-A were partially degraded. During fermentation, HEP-W and HEP-A increased the relative abundance of the dominant butyric acid-producing genera, the microbial community structure was significantly regulated, the gas production and short-chain fatty acid production in the fermentation broth were significantly increased, and the pH of the fermentation broth was reduced. There were structural and other differences in HEP-W and HEP-A due to different extraction methods, which resulted in different results. These results suggest that HEP-W and HEP-A may be potential gut microbial manipulators to promote gut health by promoting the production of beneficial metabolites by intestinal microorganisms using different butyric acid production pathways.

Sustainable production and pharmaceutical applications of β-glucan from microbial sources

β-glucans are a large class of complex polysaccharides found in abundant sources. Our dietary sources of β-glucans are cereals that include oats and barley, and non-cereal sources can consist of mushrooms, microalgae, bacteria, and seaweeds. There is substantial clinical interest in β-glucans; as they can be used for a variety of diseases including cancer and cardiovascular conditions. Suitable sources of β-glucans for biopharmaceutical applications include bacteria, microalgae, mycelium, and yeast. Environmental factors including culture medium can influence the biomass and ultimately β-glucan content. Therefore, cultivation conditions for the above organisms can be controlled for sustainable enhanced production of β-glucans. This review discusses the various sources of β-glucans and their cultivation conditions that may be optimised to exploit sustainable production. Finally, this article discusses the immune-modulatory potential of β-glucans from these sources.

Interaction of beta-glucans with gut microbiota: Dietary origins, structures, degradation, metabolism, and beneficial function

Beta-glucan (BG), a polysaccharide comprised of interfacing glucose monomers joined via beta-glycosidic linkages, can be defined as a type of dietary fiber with high specificity based on its interaction with the gut microbiota. It can induce similar interindividual microbiota responses, thereby having beneficial effects on the human body. In this paper, we review the four main sources of BG (cereals, fungi, algae, and bacteria) and their differences in structure and content. The interaction of BG with gut microbiota and the resulting health effects have been highlighted, including immune enhancement, regulation of serum cholesterol and insulin levels, alleviation of obesity and improvement of cognitive disorders. Finally, the application of BG in food products and its beneficial effects on the gut microbiota of consumers were discussed. Although some of the mechanisms of action remain unclear, revealing the beneficial functions of BG from the perspective of gut microbiota can help provide theoretical support for the development of diets that target the regulation of microbiota.

Production of a Series of Long-Chain Isomaltooligosaccharides from Maltose by Bacillus subtilis AP-1 and Associated Prebiotic Properties

Bacillus subtilis strain AP-1, which produces α-glucosidase with transglucosidase activity, was used to produce a series of long-chain isomaltooligosaccharides (IMOs) with degree of polymerization (DP) ranging from 2 to 14 by direct fermentation of maltose. A total IMOs yield of 36.33 g/L without contabacillusmination from glucose and maltose was achieved at 36 h of cultivation using 50 g/L of maltose, with a yield of 72.7%. IMOs were purified by size exclusion chromatography with a Superdex 30 Increase column. The molecular mass and DP of IMOs were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Subsequently, linkages in produced oligosaccharides were verified by enzymatic hydrolysis with α-amylase and oligo-α-1,6-glucosidase. These IMOs showed prebiotic properties, namely tolerance to acidic conditions and digestive enzymes of the gastrointestinal tract, stimulation of probiotic bacteria growth to produce short-chain fatty acids and no stimulating effect on pathogenic bacteria growth. Moreover, these IMOs were not toxic to mammalian cells at up to 5 mg/mL, indicating their biocompatibility. Therefore, this research demonstrated a simple and economical method for producing IMOs with DP2–14 without additional operations; moreover, the excellent prebiotic properties of the IMOs offer great prospects for their application in functional foods.

Interaction between β-glucans and gut microbiota: a comprehensive review

Gut microbiota (GMB) in humans plays a crucial role in health and diseases. Diet can regulate the composition and function of GMB which are associated with different human diseases. Dietary fibers can induce different health benefits through stimulation of beneficial GMB. β-glucans (BGs) as dietary fibers have gained much interest due to their various functional properties. They can have therapeutic roles on gut health based on modulation of GMB, intestinal fermentation, production of different metabolites, and so on. There is an increasing interest in food industries in commercial application of BG as a bioactive substance into food formulations. The aim of this review is considering the metabolizing of BGs by GMB, effects of BGs on the variation of GMB population, influence of BGs on the gut infections, prebiotic effects of BGs in the gut, in vivo and in vitro fermentation of BGs and effects of processing on BG fermentability.

Encapsulation of polyphenols in pH-responsive micelles self-assembled from octenyl-succinylated curdlan oligosaccharide and its effect on the gut microbiota

An amphiphilic polymer based on octenyl succinic anhydride-modified curdlan oligosaccharide (MCOS) was synthesized. The critical micelle concentration of MCOS was 3.91 μg·mL-1. MCOS could self-assemble into spherical micelles with a particle size of 230.1 nm and a zeta potential of - 37.9 mV. When used for polyphenol encapsulation, the loading capacity of curcumin and quercetin-co-encapsulated micelles was higher than that of single-polyphenol encapsulated micelles. In vitro gastrointestinal release test showed that the MCOS micelle presented a pH-dependent release, released a little polyphenol in simulated gastric fluid, but presented sustained release in the simulated intestinal fluid. The gastrointestinal-digested polyphenol-loaded micelles exhibited excellent antioxidant ability. In vitro human fecal fermentation indicated that the MCOS carrier could promote the production of short-chain fatty acids by gut microbiota and exhibited the highest relative abundance of Megamonas. In addition, the supplementation of curcumin and quercetin-co-loaded MCOS micelles increased the relative abundance of Bifidobacterium and inhibited the growth of Escherichia_Shigella. These findings indicated that the MCOS carrier can be potentially used for the colon-targeted delivery of hydrophobic polyphenols due to its pH-responsive property.

One-Pot Three-Enzyme System for Production of a Novel Prebiotic Mannosyl-β-(1 → 4)-Fructose Using a d-Mannose Isomerase from Xanthomonas phaseoli

The present supply of prebiotics is entirely inadequate to meet their demand. To produce novel prebiotics, a d-mannose isomerase (XpMIaseA) from Xanthomonas phaseoli was first produced in Komagataella phaffii (Pichia pastoris). XpMIaseA shared the highest amino acid sequence identity (58.0%) with the enzyme from Marinomonas mediterranea. Efficient secretory production of XpMIaseA (282.0 U mL^-1) was achieved using high cell density fermentation. The optimal conditions of XpMIaseA were pH 7.5 and 55 °C. It showed a broad substrate specificity, which isomerized d-mannose, d-talose, mannobiose, epilactose, and mannotriose. XpMIaseA was employed to construct a one-pot three-enzyme system for the production of mannosyl-β-(1 → 4)-fructose (MF) using mannan (5%, w/v) as the substrate. The equilibrium yield of MF was 58.2%. In in vitro fermentations, MF significantly stimulated (≤3.2-fold) the growth of 12 among 15 tested Bifidobacterium and Lactobacillus strains compared with fructo-oligosaccharides. Thus, the novel d-mannose isomerase provides a one-pot bioconversion strategy for efficiently producing novel prebiotics.

In vitro fermentation of Bangia fusco-purpurea polysaccharide by human gut microbiota and the protective effects of the resultant products on Caco-2 cells from lipopolysaccharide-induced injury

Polysaccharide extracted from red seaweed Bangia fusco-purpurea (BFP) is a novel sulfated galactan, differed from agarans and carrageenans in fine structure. In this study, in vitro fermentation characteristics of BFP by human gut microbiota and its protective effect on lipopolysaccharide (LPS)-induced injury in Caco-2 cells were investigated. Our results showed that BFP was mainly degraded at transverse colon for 18 h fermentation by gut microbiota with reduced molecular weight. Meanwhile, BFP fermentation was associated with increased short-chain fatty acids (SCFAs) as compared to control group, especially acetic acid was increased to 129.53 ± 0.24 from 82.14 ± 0.23 mmol/L, and butyric acid was up to 1.56 ± 0.004 from 0.62 ± 0.01 mmol/L. Furthermore, BFP promoted abundances of Bacteroidetes and Firmicutes, while decreased numbers of Proteobacteria. The up-regrated beneficial differential metabolites were SCFAs, L-proline, arginine, folic acid, pyridoxamine, thiamine, etc. (p < 0.05), and their related metabolic pathways mainly included mTOR, arginine biosynthesis, and vitamin metabolism. Notably, BFP fermentation products at transverse colon significantly restored cell viability of LPS-treated Caco-2 cells from 73.79 ± 0.48 % to 93.79-99.64 %, which might be caused by increased beneficial differential metabolites (e.g., SCFAs). Our findings suggest that BFP has prebiotic potential and can enhance gut health.

Revalorization of Cava (Spanish Sparkling Wine) Lees on Sourdough Fermentation

Cava lees are a sparkling wine by-product formed of dead microorganisms, tartaric acid and other inorganic compounds, with a potential for enhancing microbial growth. Lees are rich in antioxidant compounds as well as β-glucans and mannoproteins. The aim of this study was to evaluate the effect of different concentrations of cava lees (0–2% w/w) on the microbiota (LAB and yeasts) responsible for sourdough fermentation (8 days) to revalorize this by-product of the wine industry. The results showed that 2% cava lees promoted microbial growth and survival in both wheat and rye sourdoughs, except for yeast growth in rye, which stopped at day 3 of fermentation. Moreover, sourdough with lees achieved lower pH values as well as higher concentrations of organic acids, especially lactic and acetic acids (p < 0.05). To sum up, the use of cava lees in sourdough formulation promotes the growth and survival of microorganisms, which, in consequence, promotes a lower pH and greater amounts of organic acids. This could lead to microbial stability as well as changes in bread flavor.

Fermentation profile, cholesterol-reducing properties and chemopreventive potential of β-glucans from Levilactobacillus brevis and Pediococcus claussenii - a comparative study with β-glucans from different sources

The aim of the present study was to investigate whether β-glucans obtained from the lactic acid bacteria (LAB) Levilactobacillus (L.) brevis and Pediococcus (P.) claussenii exhibit similar physiological effects such as cholesterol-binding capacity (CBC) as the structurally different β-glucans from oat, barley, and yeast as well as curdlan. After in vitro fermentation, fermentation supernatants (FSs) and/or -pellets (FPs) were analyzed regarding the concentrations of short-chain fatty acids (SCFAs), ammonia, bile acids, the relative abundance of bacterial taxa and chemopreventive effects (growth inhibition, apoptosis, genotoxicity) in LT97 colon adenoma cells. Compared to other glucans, the highest CBC was determined for oat β-glucan (65.9 ± 8.8 mg g^-1, p < 0.05). Concentrations of SCFA were increased in FSs of all β-glucans (up to 2.7-fold). The lowest concentrations of ammonia (down to 0.8 ± 0.3 mmol L^-1) and bile acids (2.5-5.2 μg mL^-1) were detected in FSs of the β-glucans from oat, barley, yeast, and curdlan. The various β-glucans differentially modulated the relative abundance of bacteria families and reduced the Firmicutes/Bacteroidetes ratio. Treatment of LT97 cells with the FSs led to a significant dose-dependent growth reduction and increase in caspase-3 activity without exhibiting genotoxic effects. Though the different β-glucans show different fermentation profiles as well as cholesterol- and bile acid-reducing properties, they exhibit comparable chemopreventive effects.

Prebiotic activity of paramylon isolated from heterotrophically grown Euglena gracilis

Paramylon from Euglena gracilis is an insoluble crystalline β-1,3-glucan which have pharmaceutical and nutraceuticals applications. The present study aims to check the prebiotic potential of paramylon derived from heterotrophically grown E. gracilis in bioreactor. The Paramylon was extracted using sodium dodecyl sulfate from E. gracilis biomass. The Fourier Transform-Infra Red spectroscopy and scanning electron microscopy demonstrated the isolated paramylon to be equivalent to that of analytical standard. The prebiotic activity of E. gracilis cell extract and isolated paramylon was studied. E. gracilis cell extract as well as isolated paramylon led to cell number enhancement of Lacfid (Lactobacillus) strain exhibiting the prebiotic activities.

Growth-Promoting Effect of Cava Lees on Lactic Acid Bacteria Strains: A Potential Revalorization Strategy of a Winery By-Product

The growing trend of circular economy has prompted the design of novel strategies for the revalorization of food industry by-products. Cava lees, a winery by-product consisting of non-viable cells of Saccharomyces cerevisiae rich in β-glucans and mannan-oligosaccharides, can be used as a microbial growth promoter, with potential food safety and health applications. The aim of this study was to assess in vitro the effect of cava lees on the growth of 21 strains of lactic acid bacteria (LAB) species commonly used as starter cultures and/or probiotics. Firstly, 5% of cava lees was selected as the most effective amount for enhancing microbial counts. After screening different LAB, statistically significantly (p < 0.05) higher microbial counts were found in 12 strains as a consequence of cava lees supplementation. Moreover, a greater and faster reduction in pH was observed in most of these strains. The growth-promoting effects of cava lees on LAB strains supports the potential revalorization of this winery by-product, either to improve the safety of fermented products or as a health-promoting prebiotic that may be selectively fermented by probiotic species.

Therapeutic and Industrial Applications of Curdlan With Overview on Its Recent Patents

Curdlan is an exopolysaccharide, which is composed of glucose linked with β-(1,3)-glycosidic bond and is produced by bacteria, such as Alcaligenes spp., Agrobacterium spp., Paenibacillus spp., Rhizobium spp., Saccharomyces cerevisiae, Candida spp., and fungal sources like Aureobasidium pullulan, Poria cocos, etc. Curdlan has been utilized in the food and pharmaceutical industries for its prebiotic, viscosifying, and water-holding properties for decades. Recently, the usefulness of curdlan has been further explored by the pharmaceutical industry for its potential therapeutic applications. Curdlan has exhibited immunoregulatory and antitumor activity in preclinical settings. It was observed that curdlan can prevent the proliferation of malarial merozoites in vivo; therefore, it may be considered as a promising therapy for the treatment of end-stage malaria. In addition, curdlan has demonstrated potent antiviral effects against human immunodeficiency virus (HIV) and Aedes aegypti virus. It has been suggested that the virucidal properties of curdlans should be extended further for other deadly viruses, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2/COVID-19). The prebiotic property of curdlan would confer beneficial effects on the host by promoting the growth of healthy microbiota in the gut and consequently help to reduce gastrointestinal disorders. Therefore, curdlan can be employed in the manufacture of prebiotics for the management of various gastrointestinal dysbiosis problems. Studies on the mechanism of action of curdlan-induced suppression in microbial and tumor cells at the cellular and molecular levels would not only enhance our understanding regarding the therapeutic effectiveness of curdlan but also help in the discovery of new drugs and dietary supplements. The primary focus of this review is to highlight the therapeutic interventions of curdlan as an anticancer, anti-malaria, antiviral, and antibacterial agent in humans. In addition, our review provides the latest information about the chemistry and biosynthesis of curdlan and its applications for making novel dairy products, functional foods, and nutraceuticals and also details about the recent patents of curdlan and its derivatives.

In Vitro Fermentation Characteristics and Fiber-Degrading Enzyme Kinetics of Cellulose, Arabinoxylan, β-Glucan and Glucomannan by Pig Fecal Microbiota

Non-digestible polysaccharides are of great significance to human and animal intestinal health. Cellulose, arabinoxylan, β-glucan and glucomannan were selected in the present study to investigate the fermentation characteristics and fiber-degrading enzyme kinetics by inoculating pig fecal microbiota in vitro. Our results showed that fermentation of arabinoxylan and β-glucan produced the highest amount of acetate and lactate, respectively. The abundance of Prevotella_9 was the highest in β-glucan group and positively correlated with lactate and acetate. Glucomannan fermentation produced the highest amount of butyrate, and the abundance of Lachnospiraceae_XPB_1014_group and Bacteroides were the lowest. A significant negative correlation was found between Lachnospiraceae_XPB_1014_group, Bacteroides and butyrate. Exo-β-1,4-xylanase had the highest activity at 24 h during arabinoxylan fermentation. The activity of β-glucosidase and β-mannosidase at 36 h were higher than those at 15 h in the glucomannan group. The abundance of Prevotella_9 was positively correlated with β-glucosidase while Lachnospiraceae_XPB_1014_group and Bacteroides were negatively correlated with β-xylosidase. Our findings demonstrated the β-glucan and arabinoxylan promote proliferation of Prevotella_9, with the preference to secret β-glucosidase, β-mannosidase and the potential to produce lactate and acetate. Butyrate production can be improved by inhibiting the proliferation of Lachnospiraceae_XPB_1014_group and Bacteroides, which have the lack of potential to secret β-xylosidase.

Metabolic profiles of oligosaccharides derived from four microbial polysaccharides by faecal inocula from type 2 diabetes patients

In vitro digestion of curdlan oligosaccharides (COSs), pullulan oligosaccharides (POSs), xanthan gum oligosaccharides (XGOSs) and gellan gum oligosaccharides (GGOSs) was investigated. These four oligosaccharides showed resistance to simulated saliva and gastric and small intestinal fluid. In further fermentation with faecal microbiota from healthy subjects and type 2 diabetes (T2D) patients, COS fermentation significantly increased the abundance of Bifidobacterium spp. and Lactobacillus spp. and the production of short-chain fatty acids in healthy and T2D groups. Digestion of XGOS enhanced the growth of the Clostridium leptum subgroup and significantly increased butyric acid production in healthy and T2D groups. Sole fermentation with COS, POS, XGOS and GGOS exhibited different metabolic profiles between healthy and T2D groups, and more small molecule polyols were produced in the T2D group than in the healthy group. This study provides a novel perspective on the reconstruction of gut microbiota and metabolism by POS, COS, GGOS and XGOS intervention.

Dietary Curdlan Enhances Bifidobacteria and Reduces Intestinal Inflammation in Mice

β-glucan consumption is known for its beneficial health effects, but the mode of action is unclear. While humans and mice lack the required enzymes to digest β-glucans, certain intestinal microbes can digest β-glucans, triggering gut microbial changes. Curdlan, a particulate β-glucan isolated from Alcaligenes faecalis, is used as a food additive. In this study we determined the effect of curdlan intake in mice on the intestinal microbiota and dextran sodium sulfate (DSS)-induced intestinal inflammation. The effect of curdlan on the human intestinal microbiota was assessed using i-screen, an assay for studying anaerobic microbial interactions. Mice received oral gavage with vehicle or curdlan for 14 days followed by DSS for 7 days. The curdlan-fed group showed reduced weight loss and colonic inflammation compared to the vehicle-fed group. Curdlan intake did not induce general microbiota community changes, although a specific Bifidobacterium, closely related to Bifidobacterium choerinum, was observed to be 10- to 100-fold more prevalent in the curdlan-fed group under control and colitis conditions, respectively. When tested in i-screen, curdlan induced a global change in the microbial composition of the healthy intestinal microbiota from a human. Overall, these results suggest that dietary curdlan induces microbiota changes that could reduce intestinal inflammation.

Systematic assessment of oat β-glucan catabolism during in vitro digestion and fermentation

β-Glucan as a component of grain cell walls is consumed daily. However, little is known about whether β-glucan is influenced by the gastrointestinal environment. In this study, we aim to investigate the integrated metabolic process of cereal β-glucan. In vitro simulated digestion and fermentation combined with microbiome and metabolome analysis were used to profile the metabolism of β-glucan. Intriguingly, we found that β-glucan was not hydrolyzed by digestive enzymes but partially degraded by gastric acid environment during in vitro digestion. Moreover, β-glucan was utilized by gut microbiota to produce acetate, propionate and butyrate, concurrently, the relative abundance of Lactobacillus significantly increased and Escherichia-Shigella significantly decreased. The correlation analysis between metabolomics datasets and microorganisms revealed that β-glucan catabolism was also accompanied by amino acid catabolism and linoleic acid biosynthesis. Our study offered a forceful basis for the further exploration of the role of β-glucan and gut microbiota in host health.

Effects of Laetiporus sulphureus-Fermented Wheat Bran on Growth Performance, Intestinal Microbiota and Digesta Characteristics in Broiler Chickens

Simple Summary

This study investigated the effects of a Laetiporussulphureus-fermented wheat bran (LS) supplementation on the microbiota and digesta characteristics of broiler chickens. Results showed that a 5% LS supplementation could potentially enhance the feed conversion ratio and European Broiler Index (EBI) of the broilers by elevating the family Lactobacillaceae and suppressing the phylum Proteobacteria’s population. This could also change the intestinal environments by elevating the ileal and cecal lactic acid concentrations as well as lowering the pH and ammonium nitrate, thereby potentially favoring the growth and health of the broilers.

Abstract

This study investigated the effects of a Laetiporus sulphureus-fermented wheat bran (LS) supplementation on the microbiota and digesta characteristics of broiler chickens. Two hundred and forty male broilers (Ross 308) were randomly allocated into three groups fed with a corn–soybean-based diet (control), and the control diet being replaced with 5% wheat bran (WB) and 5% LS, respectively. Each group had four replicates and 20 birds per pen. Metagenomics analysis results of the ileum microbiota showed that, at the family level, the 5% LS groups had over 40% higher Lactobacillaceae compared to the control group in a mean difference comparison. Heat maps showed that, at the phylum level, the population of Firmicutes was higher and Proteobacteria was lower in the ileum of 5% LS compared to the control group. Results of the stack column plots of the top ten OTUs at the family level showed that a 5% LS and 5% WB supplementation altered the broiler microbiota distribution by increasing the relative abundance of Lactobacillaceae. Cecal microbiota analysis showed that the 5% LS-supplemented group had approximately 5% and 3% higher Veillonellaceae and Lactobacillaceae, respectively. Stack column plots of the top ten OTUs indicated that the distribution of cecal bacteria in each group was not markedly different. Both the ileum and cecum digesta in the 5% LS supplementation group had a slight and not significant elevation on the total VFA, while the pH values and ammonia nitrogen were significantly lowered compared to the control and 5% WB groups (p < 0.05). In addition, the 5% LS supplementation group had a significantly higher lactic acid concentration in both the ileum and cecum compared to the control and 5% WB groups (p < 0.05). In conclusion, a 5% LS supplementation could potentially enhance the feed conversion ratio and European Broiler Index (EBI) of broilers by elevating the family Lactobacillaceae and suppressing the phylum Proteobacteria’s population, thus creating changed intestinal environments that may potentially favor the growth and health of the broilers.

Bringing the digestibility of prebiotics into focus: update of carbohydrate digestion models

Oro-gastrointestinal digestion of dietary carbohydrates involves up to six different carbohydrases in a multistage process. Enzymes from the small intestinal brush border membrane play a major role in the digestibility of these substrates. However, to date, the inclusion of these small intestinal enzymes has been dismissed in most in vitro studies carried out, despite their importance in the degradation of carbohydrates. Several in vitro and in vivo studies have demonstrated the capability of brush border enzymes to degrade certain "non-digestible" carbohydrates to a different extent depending on their structural composition (monomeric composition, glycosidic linkage, etc.). In this sense, considering the available evidence, mucosal disaccharidases embedded in the small intestinal brush border membrane vesicles must be considered in addition to α-amylases; therefore, new approaches for the evaluation of the digestibility of carbohydrates have been recently reported. These new methods based on the utilization of the small intestinal enzymes present in the brush border membrane aim to fulfill the final and key step of the digestion of carbohydrates in the small intestine. Here, rat small intestinal extract enzymes as well as brush border membrane vesicles from pig have emerged as very reliable and useful tools to evaluate carbohydrate digestion. Thus, this review aims to go briefly through the most relevant digestion methods for carbohydrates that are currently available and to highlight the new improved methods, which include mammalian intestinal enzymes, and their current use in the evaluation of the digestibility of prebiotics.

In vitro prebiotic potential, digestibility and biocompatibility properties of laminari-oligosaccharides produced from curdlan by β-1,3-endoglucanase from Clostridium thermocellum

Curdlan or laminarin, a β-1,3-glucan was hydrolysed by β-1,3-endoglucanase (CtLam81A) from Clostridium thermocellum to produce laminari-oligosaccharides. TLC analysis of hydrolysed curdlan showed the presence of laminari-oligosaccharides of the degree of polymerization, DP2-DP7. This mixture of laminari-oligosaccharides displayed prebiotic properties. Laminari-oligosaccharides showed an increase in the growth of probiotic bacteria such as Lactobacillus plantarum DM5 and Lactobacillus acidophilus, while they did not promote the growth of non-probiotic bacteria (Escherichia coli and Enterobacter aerogenes). Laminari-oligosaccharides showed higher prebiotic activity score of 0.92 ± 0.01 and 0.64 ± 0.08 for L. plantarum DM5 and L. acidophilus NRRL B-4496, respectively, similar to those shown by inulin. Laminari-oligosaccharides showed higher resistance or low digestibility against α-amylase, artificial gastric juice and intestinal fluid than inulin indicating their bioavailability to the probiotic bacteria present in the gastrointestinal tract of human. The probiotic bacteria consumed laminaribiose and laminariotriose more readily than higher laminari-oligosaccharides as carbon source for their growth. The in vitro cytotoxicity assay of laminari-oligosaccharides (1 mg/ml) on human embryonic kidney (HEK 293) cells showed that the cell viability was not affected even after 72 h indicating their biocompatible nature. All the results amply indicated that laminari-oligosaccharides can serve as potential prebiotic additives for functional food products.

Taxogenomic assessment and genomic characterisation of Weissella cibaria strain 92 able to metabolise oligosaccharides derived from dietary fibres

The importance of the gut microbiota in human health has led to an increased interest to study probiotic bacteria. Fermented food is a source of already established probiotics, but it also offers an opportunity to discover new taxa. Four strains of Weissella sp. isolated from Indian fermented food have been genome sequenced and classified into the species W. cibaria based on whole-genome phylogeny. The genome of W. cibaria strain 92, known to utilise xylooligosaccharides and produce lactate and acetate, was analysed to identify genes for oligosaccharide utilisation. Clusters including genes involved in transportation, hydrolysis and metabolism of xylooligosaccharides, arabinooligosaccharides and β-glucosides were identified. Growth on arabinobiose and laminaribiose was detected. A 6-phospho-β-glucosidase clustered with a phosphotransferase system was found upregulated during growth on laminaribiose, indicating a mechanism for laminaribiose utilisation. The genome of W. cibaria strain 92 harbours genes for utilising the phosphoketolase pathway for the production of both acetate and lactate from pentose and hexose sugars but lacks two genes necessary for utilising the pentose phosphate pathway. The ability of W. cibaria strain 92 to utilise several types of oligosaccharides derived from dietary fibres, and produce lactate and acetate makes it interesting as a probiotic candidate for further evaluation.

Chemistry and microbial sources of curdlan with potential application and safety regulations as prebiotic in food and health

Curdlan - a homopolysaccharide is comprised of glucose using β-1,3-glycosidic bond and produced by different types of microorganisms as exopolysaccharide. Curdlan gel is stable during freezing and thawing processes which find several applications in food and pharmaceutical industries. It acts as a prebiotic, stabilizer and water-holding, viscosifying and texturing agent. Additionally, curdlan gel is used as a food factor to develop the new products e.g. milk fat substitute, non-fat whipped cream, retorting (freeze-drying) process of Tofu, low-fat sausage, and low-fat hamburger. However, a great variation exists among different countries regarding the regulatory aspects of curdlan as food additives, dietary components or prebiotic substances. Therefore, the present review paper aims to discuss safety issues and the establishment of common guidelines and legislation globally, focusing on the use the applications of curdlan in the food sector including the development of noodles, meat-based products, and fat-free dairy products. This review analyzes and describes in detail the potential of curdlan as a sustainable alternative additive in health and food industries, emphasizing on the chemical composition, production, properties, and potential applications.

Evaluation of the impact of a rat small intestinal extract on the digestion of four different functional fibers

The degree of digestion, modulated by rat small intestinal extract on different functional fibers was investigated.

Curdlan (Alcaligenes faecalis) (1→3)-β-d-Glucan Oligosaccharides Drive M1 Phenotype Polarization in Murine Bone Marrow-Derived Macrophages via Activation of MAPKs and NF-κB Pathways

Functional oligosaccharides, particularly curdlan (1→3)-β-d-glucan oligosaccharides (GOS), play important roles in modulating host immune responses. However, the molecular mechanisms underlying the immunostimulatory effects of GOS on macrophage polarization are not clear. In this work, GOS (5–1000 µg/mL) were non-toxic to bone marrow-derived macrophages (BMDMs) with improved pinocytic and bactericidal capacities. Incubation with GOS (100 µg/mL) induced M1 phenotype polarization of BMDMs as evidenced by increased CD11c⁺/CD86⁺ (10.1%) and M1 gene expression of inducible nitric oxide synthase, interleukin (IL)-1β, and chemokine C-C-motif ligand 2. Accordingly, the secretion of cytokines IL-1β, IL-6, monocyte chemotactic protein-1, and tumor necrosis factor-α, as well as the nitrite release of BMDMs were increased by GOS (100 µg/mL). Expression of mitogen-activated protein kinases (MAPKs) of phosphorylated (p)-c-Jun amino-terminal kinase, p-extracellular signal regulated kinase, and p-p38 in BMDMs were increased by GOS, as well as the p-Stat1. Moreover, nuclear factor-kappa B (NF-κB) p-p65 expression in BMDMs was promoted by GOS while it suppressed IκBα expression. Receptor blocking with anti-CR3 (CD11b/CD18) and anti-toll-like receptor (TLR) 2 antibodies diminished GOS induced M1 phenotype polarization with reduced mRNA expression of M1 genes, decreased cytokine and nitrite releases, and suppressed signaling pathway activation. Thus, CR3 (CD11b/CD18) and TLR2 mediated activation of MAPKs and NF-κB pathways are responsible for GOS induced polarization of BMDMs.