Structural diversity of fungal glucans

Formulation, Characterization and Optimization of β-Glucan and Pomegranate Juice Based Films for Its Potential in Diabetes

The aim of this study was to develop films based on β-glucans in association with pomegranate juice for its potential in metabolic disorders such as diabetes due to plenty of bioactive compounds from the film composition. Initially, a Box-Behnken design was generated by varying the level of β-glucan content (0.5, 1, 1.5 g), sodium alginate (0.2, 0.4, 0.6 g) and pomegranate juice (10, 20, 30 mL) for development of films. Subsequently, glycerin was added as 25% of the total dry matter. The optimization of the films prepared by the solvent casting method was conducted based on the different responses such as: water vapor transmission rate (WVTR), water vapor permeability (WVP), thickness, density, moisture content, solubility, film opacity and color. The water activity profile and FT-IR analysis were performed in all tests. The model was used to determine the optimal experimental values considering that the optimal film will make a sustained contribution to diabetes. The optimal values of the film sample made of β-glucans, sodium alginate, pomegranate juice and glycerin make it befitting for packaging dry powdered pharmaceuticals. Finally, antimicrobial activity against Gram-negative and Gram-positive bacteria, UV barrier properties and microcrack and pore detections through SEM were also investigated for the optimal film sample.

Evaluation of the biological activities of β-glucan isolated from Lentinula edodes

Lentinula edodes (shiitake) is an edible mushroom that contains many constituents and β-glucan is considered a major polysaccharide. This study, therefore, aimed to characterize β-glucan and evaluate its activities. Fresh fruit bodies of L. edodes were used for β-glucan extraction and followed by analyses via Fourier transform infrared, Nuclear magnetic resonance, and High Performance Liquid Chromatography confirming its characteristic structure. For evaluating biological activities of β-glucan, different concentrations (0.1-3.5 mg ml^-1 ) were assessed. The optimal dose was 3.5 mg ml^-1 that showed the highest scavenging radical ability (75.3%) confirms antioxidant activity, strong inhibition of the peroxyl radical (80.9%) to inhibit lipid peroxidation, elevation the inhibition percentage of both α-amylase (73.4%) and α-glucosidase (70.3%) indicates the antidiabetic properties, and highest AFB1 reduction (88%) which ensured the aflatoxin-detoxifying ability. In addition, antifungal activity of β-glucan was evaluated to inhibit sporulation process in Aspergillus niger and recorded with minimum inhibitory concentration of 2.5 mg ml^-1 and minimum fungicidal concentration of 3 mg ml^-1 . In a dose-dependent manner, higher concentration of β-glucan affects viability of tumor cells concomitant induces potent anti-cancer immune responses and inhibited the activity of topoisomerase I which are considered an important target for cancer chemotherapy. Therefore, L. edodes-β-glucan has the potential to act as a suggestive agent for antioxidant, antidiabetic, antifungal activity, and aflatoxin detoxification.

Structural characterization and hepatoprotective activity of an acidic polysaccharide from Ganoderma lucidum

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Ganoderma lucidum crude polysaccharide (GLP) exhibited protective effect on liver damage in mice caused by restraint stress through improving oxidative status.

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Two polysaccharides, including a neutral β-glucan and an acidic β-glucan containing glucuronic acid were purified from GLP by anion-exchange chromatography (AEC) and gel filtration.

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Acidic polysaccharide demonstrated stronger hepatoprotective effect in vitro compared to neutral polysaccharide.

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Anion-exchange chromatography (AEC) is an effective technique for separate β-glucan into neutral and ionic fractions by different ionic strength buffer.

In this study, Ganoderma lucidum crude polysaccharide (GLP) was found to have protective effect on liver damage in mice caused by restraint stress through improving oxidative status. Two polysaccharides, including a neutral β-glucan (GLPB2) and an acidic β-glucan (GLPC2) were purified from GLP through anion-exchange chromatography (AEC) combined with gel permeation. GLPC2, with an average molecular weight of 20.56 kDa, exhibited stronger hepatoprotective effect against H₂O₂-induced liver injury in HepG2 cells compared to GLPB2. Glycosidic residues and NMR analysis comprehensively revealed that GLPC2 contained d-Glcp-(1→, →3)-d-Glcp-(1→, →4)-d-Glcp-(1→, →6)-d-Glcp-(1→, →3, 6)-d-Glcp-(1 → and → 4)-d-GlcpA-(1 → . AEC can be an effective technique for separating β-glucans into neutral and acidic fractions by different ionic strength buffer. The findings provided a theoretical basis for the potential application of G. lucidum polysaccharides as a hepatoprotective in food and pharmaceutical industry.

Polysaccharides from Basidiocarps of the Polypore Fungus Ganoderma resinaceum: Isolation and Structure

In this study, we focused on the isolation and structural characterization of polysaccharides from a basidiocarp of polypore fungus Ganoderma resinaceum. Polysaccharide fractions were obtained by successive extractions with cold water at room temperature (20 °C), hot water under reflux (100 °C), and a solution of 1 mol L-1 sodium hydroxide. The purity of all fractions was controlled mainly by Fourier transform infrared (FTIR) spectroscopy, and their composition and structure were characterized by organic elemental analysis; neutral sugar and methylation analyses by gas chromatography equipped with flame ionization detector (GC/FID) and mass spectrometry detector (GC/MS), respectively; and by correlation nuclear magnetic resonance (NMR) spectroscopy. The aqueous extracts contained two main polysaccharides identified as a branched O-2-β-d-mannosyl-(1→6)-α-d-galactan and a highly branched (1→3)(1→4)(1→6)-β-d-glucan. Mannogalactan predominated in the cold water extract, and β-d-glucan was the main product of the hot water extract. The hot water soluble fraction was further separated by preparative anion exchange chromatography into three sub-fractions; two of them were identified as branched β-d-glucans with a structure similar to the corresponding polysaccharide of the original fraction. The alkaline extract contained a linear (1→3)-α-d-glucan and a weakly branched (1→3)-β-d-glucan having terminal β-d-glucosyl residues attached to O-6 of the backbone. The insoluble part after all extractions was identified as a polysaccharide complex containing chitin and β-d-glucans.

Extrusion-based additive manufacturing of fungal-based composite materials using the tinder fungus Fomes fomentarius

BACKGROUND

Recent efforts in fungal biotechnology aim to develop new concepts and technologies that convert renewable plant biomass into innovative biomaterials. Hereby, plant substrates become metabolized by filamentous fungi to transform them into new fungal-based materials. Current research is thus focused on both understanding and optimizing the biology and genetics underlying filamentous fungal growth and on the development of new technologies to produce customized fungal-based materials.

RESULTS

This manuscript reports the production of stable pastes, composed of Fomes fomentarius mycelium, alginate and water with 71 wt.% mycelium in the solid content, for additive manufacturing of fungal-based composite materials. After printing complex shapes, such as hollow stars with up to 39 mm in height, a combination of freeze-drying and calcium-crosslinking processes allowed the printed shapes to remain stable even in the presence of water. The printed objects show low bulk densities of 0.12 ± 0.01 g/cm3 with interconnected macropores.

CONCLUSIONS

This work reports for the first time the application of mycelium obtained from the tinder fungus F. fomentarius for an extrusion-based additive manufacturing approach to fabricate customized light-weight 3D objects. The process holds great promise for developing light-weight, stable, and porous fungal-based materials that could replace expanded polystyrene produced from fossil resources.

Synthesis of branched β-1,3-glucan oligosaccharide with narrow degree of polymerization by fungi co-cultivation

The large molecular weight and poor water solubility of β-1,3-glucan impede its potential applications. In this study, the β-1,3-glucan producing fungi and Trichoderma harzianum capable of secreting endo-β-1,3-glucanase were co-cultivated to produce branched β-1,3-glucan oligosaccharides (bOβGs) by fermentation with Sclerotium rolfsii and Schizophyllum commune. The highest bOβG yields from S. rolfsii in flasks were 4.53 and 9.94 g/L in a 7 L fermenter. Structural analysis proved that bOβG from S. rolfsii had a narrow degree of polymerization of 5-12, whereas bOβG from S. commune had a degree of polymerization of 5-15. Antioxidant tests showed that both bOβGs had remarkable DPPH radical scavenging activity and hydroxyl radical scavenging activity, and the activity of bOβG from S. commune was better than that of bOβG from S. rolfsii. In addition, bOβGs could promote the secretion of NO by mouse macrophages and increase the production of TNF-α, IL-1β, and IL-6 in RAW264.7.

Structural insights into the substrate recognition and catalytic mechanism of a fungal glycoside hydrolase family 81 β-1,3-glucanase

β-1,3-Glucan constitutes a prominent cell wall component being responsible for rigidity and strength of the cell wall structure in filamentous fungi. Glycoside hydrolase (GH) family 81 endo-β-1,3-glucanases which can cleave the long chain of β-1,3-glucans play a major role in fungal cell wall remodeling. Here, we reported the complex structures of a fungal GH family 81 endo-β-1,3-glucanase from Rhizomucor miehei (RmLam81A), revealing the triple-helical β-glucan recognition and hydrolysis patterns. In the crystals, three structured oligosaccharide ligands simultaneously interact with one enzyme molecular via seven glucose residues, and the spatial arrangement of ligands to RmLam81A was almost identical to that of β-1,3-glucan triple-helical structure. RmLam81A performed an inverting catalysis mechanism with Asp475 and Glu557 severing as the general acid and base catalyst, respectively. Furthermore, two hydrophobic patches involving Tyr93, Tyr106, Ile108, Phe619 and Tyr628 alongside the ligand-binding site possibly formed parts of the binding site. A ligand-binding motif, β31-β32, consisting of two key residues (Lys622 and Asp624), involved the recognition of a triple-helical β-glucan. Our results provided a structural basis for the unique β-1,3-glucan recognition pattern and catalytic mechanism of fungal GH family 81 endo-β-1,3-glucanases, which may be helpful in further understanding the diverse physiological functions of β-1,3-glucanases.

Configured for the Human Gut Microbiota: Molecular Mechanisms of Dietary β-Glucan Utilization

The β-glucans are a disparate group of structurally diverse polysaccharides, whose members are widespread in human diets as components of the cell walls of plants, algae, and fungi (including yeasts), and as bacterial exopolysaccharides. Individual β-glucans from these sources have long been associated with positive effects on human health through metabolic and immunological effects. Remarkably, the β-configured glucosidic linkages that define these polysaccharides render them inaccessible to the limited repertoire of digestive enzymes encoded by the human genome. As a result, the various β-glucans become fodder for the human gut microbiota (HGM) in the lower gastrointestinal tract, where they influence community composition and metabolic output, including fermentation to short chain fatty acids (SCFAs). Only recently, however, have the specific molecular systems that enable the utilization of β-glucans by select members of the HGM been fully elucidated by combined genetic, biochemical, and structural biological approaches. In the context of β-glucan structures and their effects on human nutrition and health, we summarize here the functional characterization of individual polysaccharide utilization loci (PULs) responsible for the saccharification of mixed-linkage β(1→3)/β(1→4)-glucans, β(1→6)-glucans, β(1→3)-glucans, β(1→2)-glucans, and xyloglucans in symbiotic human gut bacteria. These exemplar PULs serve as well-defined biomarkers for the prediction of β-glucan metabolic capability in individual bacterial taxa and across the global human population.

Comparison of cell wall polysaccharides in Schizophyllum commune after changing phenotype by mutation

The Agaricomycetes fungi produce various compounds with pharmaceutical, medicinal, cosmetic, environmental and biotechnological properties. In addition, some polysaccharides extracted from the fungal cell wall have antitumor and immunomodulatory actions. The aim of this study was to use genetic modification to transform Schizophyllum commune and identify if the phenotype observed (different from the wild type) resulted in changes of the cell wall polysaccharides. The plasmid pUCHYG-GPDGLS, which contains the Pleurotus ostreatus glucan synthase gene, was used in S. commune transformations. Polysaccharides from cell wall of wild (ScW) and mutants were compared in this study. Polysaccharides from the biomass and culture broth were extracted with hot water. One of the mutants (ScT4) was selected for further studies and, after hydrolysis/acetylation, the GLC analysis showed galactose as the major component in polysaccharide fraction from the mutant and glucose as the major monomer in the wild type. Differences were also found in the elution profiles from HPSEC and NMR analyses. From the monosaccharide composition it was proposed that mannogalactans are components of S. commune cell wall for both, wild and mutant, but in different proportions. To our knowledge, this is the first time that mannogalactans are isolated from S. commune liquid culture.

Recent advances in enzymatic synthesis of β-glucan and cellulose

Bottom-up synthesis of β-glucans such as callose, fungal β-(1,3)(1,6)-glucan and cellulose, can create the defined compounds that are needed to perform fundamental studies on glucan properties and develop applications. With the importance of β-glucans and cellulose in high-profile fields such as nutrition, renewables-based biotechnology and materials science, the enzymatic synthesis of such relevant carbohydrates and their derivatives has attracted much attention. Here we review recent developments in enzymatic synthesis of β-glucans and cellulose, with a focus on progress made over the last five years. We cover the different types of biocatalysts employed, their incorporation in cascades, the exploitation of enzyme promiscuity and their engineering, and reaction conditions affecting the production as well as in situ self-assembly of (non)functionalised glucans. The recent achievements in the application of glycosyl transferases and β-1,4- and β-1,3-glucan phosphorylases demonstrate the high potential and versatility of these biocatalysts in glucan synthesis in both industrial and academic contexts.

Identification of the Primary Structure of Selenium-Containing Polysaccharides Selectively Inhibiting T-Cell Proliferation

We previously described the biosynthesis, isolation, and immunosuppressive activity of the selenium-containing polysaccharide fraction isolated from the mycelial culture of Lentinula edodes. Structural studies have shown that the fraction was a protein-containing mixture of high molar mass polysaccharides α- and β-glucans. However, which of the components of the complex fraction is responsible for the immunosuppressive activity non-typical for polysaccharides of fungal origin has not been explained. In the current study, we defined four-polysaccharide components of the Se-containing polysaccharide fraction determined their primary structure and examined the effect on T- and B-cell proliferation. The isolated Se-polysaccharides, α-1,4-glucan (M_w 2.25 × 10⁶ g/mol), unbranched β-1,6-d-glucan, unbranched β-1,3-d-glucan and β-1,3-branched β-1,6-d-glucan (M_w 1.10 × 10⁵ g/mol), are not typical as components of the cell wall of L. edodes. All are biologically active, but the inhibitory effect of the isolated polysaccharides on lymphocyte proliferation was weaker, though more selective than that of the crude fraction.

Health-Promoting of Polysaccharides Extracted from Ganoderma lucidum

Medicinal mushrooms are rich sources of pharmacologically active compounds. One of the mushrooms commonly used in traditional Chinese medicine is Ganoderma lucidum (Leyss. Ex Fr.) Karst. In Asian countries it is treated as a nutraceutical, whose regular consumption provides vitality and improves health. Ganoderma lucidum is an important source of biologically active compounds. The pharmacologically active fraction of polysaccharides has antioxidant, immunomodulatory, antineurodegenerative and antidiabetic activities. In this review, we summarize the activity of Ganoderma lucidum polysaccharides (GLP).

Production, characterization and bio-emulsifying application of exopolysaccharides from Rhodotorula mucilaginosa YMM19

Microbial exopolysaccharides (EPS) are high molecular weight polymers having different sugar residues. EPS have potential applications in different fields, such as medicine, food and environment. Therefore, there is a growing interest in production, characterization and application of EPS from different microorganisms. The present study designed to investigate the production and characterization of EPS from Rhodotorula mucilaginosa YMM19 isolated from Morus nigra L. fruits as well as to examine their potential emulsifying properties. Effect of NaCl concentration, incubation period and pH on the production of EPS was studied. The maximum EPS production by yeast was achieved at 10% NaCl (9741.84 mg/l). The best incubation time for production of EPS was 5 days. Production of EPS decreased under neutral condition and increased at acidic and alkaline condition. The structural feature of EPS was examined by FT-IR and NMR spectral analysis and confirmed the presence of glucose, glucopyranose and galactose. The isolated EPS showed higher emulsification capacity with emulsification activity of 71% and emulsifying index of 60%. The EPS gave strong emulsification for farnesol and was more effective than sodium dodecyl sulphate, a reference emulsifier, in enhancing the herbicidal activity of farnesol against Melilotus indicus under greenhouse condition. The results suggest that the EPS produced by YMM19 strain has a potential to be used as emulsifying agent in pesticide formulations.

Prebiotic potential of mushroom d-glucans: implications of physicochemical properties and structural features

Mushroom d-glucans are recognized as dietary fibers and as biologically active natural polysaccharides, with the advantages of being quite inexpensive for production, tolerable, and having a range of possible structures and physicochemical properties. The prebiotic potential of mushroom d-glucans has been explored in recent years, but the relationship between their various structural features and activity is poorly understood. This review focuses on comprehensively evaluating the prebiotic potential of mushroom d-glucans in face of their structural variations. Overall, mushroom d-glucans provide a unique set of different structures and physicochemical properties with prebiotic potential, where linkage type and solubility degree seem to be associated with prebiotic activity outcomes. The understanding of the effects of distinct structures and physicochemical properties in mushroom d-glucans on the gut microbiota contributes to the design and selection of new prebiotics in a more predictable way.

The detection, purity and structural properties of partially soluble mushroom and cereal β-D-glucans: A solid-state NMR study

β-D-glucans are proposed to have many health benefits. It is therefore important to have methods which can distinguish these from other carbohydrates present in natural products, as well as giving glucan content and structural information. Correlations between features in the CP/MAS spectra of β-D-glucans and enzyme assay determined β-D-glucan content were generally found to be poor. The β-D-glucan in dry and hydrated forms of the mushroom Ganoderma lucidum was investigated in detail by spectral peak fitting to the anomeric carbon C1 region in CP/MAS NMR spectra. Hydrated samples gave spectra with enhanced resolution and suggested that a clear distinction between β-D-glucans and other carbohydrates could be possible in the anomeric carbon C1 region. Chemical shift values for a range of carbohydrate polymers, which can be found alongside β-D-glucans, as well as the values for various linkages are given. Contamination by other carbohydrates and buffer salts is discussed.

Structural characterization and immunomodulatory mechanisms of two novel glucans from Morchella importuna fruiting bodies

Two novel glucans named MIPB50-W and MIPB50-S-1 were obtained from edible Morchella importuna with molecular weights (M_w) of 939.2 kDa and 444.5 kDa, respectively. MIPB50-W has a backbone of α-(1 → 4)-d-glucan, which was substituted at O-6 position by α-d-Glcp-(1→. Moreover, MIPB50-S-1 has a backbone of α-(1 → 4)-d-glucan, which was substituted at O-6 position by α-d-Glcp-(1 → 6)-α-d-Glcp-(1→. This is the first report about glucan found in Morchella mushrooms. Furthermore, MIPB50-W and MIPB50-S-1 strengthened the phagocytosis function and the promoted secretion of interleukins (IL)-6/tumor necrosis factor-alpha (TNF-α) and nitric oxide (NO), which induced the activation of Toll-like receptor 2 (TLR2), TLR4 as well as mitogen activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways. Interestingly, MIPB50-S-1 performed the better immunomodulatory activity than that of MIPB50-W in almost all tests. Therefore, MIPB50-W and MIPB50-S-1 are potential immune-enhancing components of functional foods.

Structural analysis and biological effects of a neutral polysaccharide from the fruits of Rosa laevigata

A neutral water-soluble polysaccharide (RLP50-2) was extracted and purified from the fruits of Rosa laevigata. The absolute molecular weight was determined as 1.26 × 10⁴ g/mol. Monosaccharide composition analysis showed that RLP50-2 mainly consisted of glucose, arabinose, and galactose. Structural analysis revealed that RLP50-2 consisted of →5)-α-L-Araf-(1→, →2,5)-α-L-Araf-(1→, →3,5)-α-L-Araf-(1→, →4)-α-D-Glcp-(1→, →6)-α-D-Glcp-(1→, →3,6)-β-D-Glcp-(1→, →4)-α-D-Galp-(1→, →6)-β-D-Galp-(1→, →2)-β-D-Xylp-(1→, terminal α-L-arabinose, and terminal β-D-mannose. Biological assays showed that RLP50-2 had immunomodulatory activities using cell and zebrafish models. Moreover, RLP50-2 showed significantly antitumor activities by inhibiting tumor cell proliferation and migration and blocking angiogenesis. These results suggested that RLP50-2 could be developed as a potential immunomodulatory agent or antitumor candidate drug in biomedicine field.

A comprehensive review on α-D-Glucans: Structural and functional diversity, derivatization and bioapplications

Glucans are the most abundant natural polysaccharides across the living kingdom with tremendous biological activities. Now a days, α-D-glucans are gaining importance as a prebiotics, nutraceuticals, immunostimulants, antiproliferative agents and biodegradable polymers in pharmaceutical and cosmetic sectors. A wide variety of bioresources including bacteria, fungi, lichens, algae, plants and animals produce α-D-glucans either as an exopolysaccharide (EPS) or a cell wall component or an energy storage polymer. The α-D-glucans exhibit great structural and functional diversity as the type of linkage and percentage of branching dictate the functional properties of glucans. Among the different linkages, bioactivities are greatly confined to the α-D-(1 → 3) linkages whereas starch and other polymers consisting of α-D-(1 → 4) (1 → 6) linkages are specific for food and pharmaceutical applications. However, the bioactivities of the α-D-(1 → 3) glucans in native form is limited mainly due to their hydrophobic nature. Hence several derivatization techniques have been developed to improve the bioavailability as well as bioactive features such as antiviral, antimicrobial, anti-inflammatory, antioxidant, immunomodulatory and antitumor properties. Though, several reports have presented about α-D-glucans, still there is an ambiguity in terms of their structure among different natural sources and moreover no comprehensive information was available on their derivatization techniques and application potential. Therefore, the present review summarizes distinct description on diverse sources, type of linkages, derivatization techniques as well as the application potential of the native and modified α-D-glucans.

β-Glucans as a panacea for a healthy heart? Their roles in preventing and treating cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Factors increasing the risks for CVD development are related to obesity, diabetes, high blood cholesterol, high blood pressure and lifestyle. CVD risk factors may be treated with appropriate drugs, but prolonged can use cause undesirable side-effects. Among the natural products used in complementary and alternative medicines, are the β-ᴅ-glucans; biopolymers found in foods (cereals, mushrooms), and can easily be produced by microbial fermentation. Independent of source, β-glucans of the mixed-linked types [(1 → 3)(1 → 6)-β-ᴅ-glucans - fungal, and (1 → 3)(1 → 4)-β-ᴅ-glucans - cereal] have widely been studied because of their biological activities, and have demonstrated cardiovascular protective effects. In this review, we discuss the roles of β-ᴅ-glucans in various pathophysiological conditions that lead to CVDs including obesity, dyslipidemia, hyperglycemia, oxidative stress, hypertension, atherosclerosis and stroke. The β-glucans from all of the sources cited demonstrated potential hypoglycemic, hypocholesterolemic and anti-obesogenicity activities, reduced hypertension and ameliorated the atherosclerosis condition. More recently, β-glucans are recognized as possessing prebiotic properties that modulate the gut microbiome and impact on the health benefits including cardiovascular. Overall, all the studies investigated unequivocally demonstrated the dietary benefits of consuming β-glucans regardless of source, thus constituting a promising panaceutical approach to reduce CVD risk factors.

Production of β-glucan exopolysaccharide lasiodiplodan by Lasiodiplodia theobromae CCT 3966 from corn bran acid hydrolysate

The potential utilization of corn bran acid hydrolysate (CBAH) was evaluated as an inexpensive feedstock for the production of a rich carbohydrate and protein medium for lasiodiplodan (LAS) production using the filamentous fungus Lasiodiplodia theobromae CCT 3966. Experiments were performed according to a 2² CCRD experimental design aiming to evaluate the influence of agitation speed (rpm) and temperature (°C) over the production of total cell biomass (TCB) and LAS concentration released to the medium (LAS-M), adhered to biomass (LAS-C), and total (LAS-T). Under the selected conditions (temperature of 28°C and agitation of 200 rpm), 8.73 g·L^-1 of LAS-T and 4.47 g·L^-1 of TCB were obtained. Recovery of LAS-C with hot water was shown as an alternative to increase the production concentration, although it might require further purification steps. CBAH potential for substitution of synthetic media was demonstrated, indicating that it is an adequate raw material containing all necessary nutrients for LAS production.Key points• Corn bran acid hydrolysate is presented as a suitable substrate for β-glucan production.• Lasiodiplodia theobromae CCT 3966 have the potential for the industrial β-glucan production.• Simple recovering of biomass-adhered lasiodiplodan by hot water extraction.

Split Enzyme-Based Biosensors for Structural Characterization of Soluble and Insoluble β-Glucans

β-Glucan is widely distributed in various plants and microorganisms and is composed of β-1,3-linked d-glucose units. It may have a branched short or long side chain of glucose units with β-1,6- or β-1,4-linkage. Numerous studies have investigated different β-glucans and revealed their bioactivities. To understand the structure-function relationship of β-glucan, we constructed a split-luciferase complementation assay for the structural analysis of long-chain β-1,6-branched β-1,3-glucan. The N- and C-terminal fragments of luciferase from deep-sea shrimp were fused to insect-derived β-1,3-glucan recognition protein and fungal endo-β-1,6-glucanase (Neg1)-derived β-1,6-glucan recognition protein, respectively. In this approach, two β-glucan recognition proteins bound to β-glucan molecules come into close proximity, resulting in the assembly of the full-length reporter enzyme and induction of transient luciferase activity, indicative of the structure of β-glucan. To test the applicability of this assay, β-glucan and two β-glucan recognition proteins were mixed, resulting in an increase in the luminescence intensity in a β-1,3-glucan with a long polymer of β-1,6-glucan in a dose-dependent manner. This simple test also allows the monitoring of real-time changes in the side chain structure and serves as a convenient method to distinguish between β-1,3-glucan and long-chain β-1,6-branched β-1,3-glucan in various soluble and insoluble β-glucans.

Spent Brewer's Yeast as a Source of Insoluble β-Glucans

In the brewing process, the consumption of resources and the amount of waste generated are high and due to a lot of organic compounds in waste-water, the capacity of natural regeneration of the environment is exceeded. Residual yeast, the second by-product of brewing is considered to have an important chemical composition. An approach with nutritional potential refers to the extraction of bioactive compounds from the yeast cell wall, such as β-glucans. Concerning the potential food applications with better textural characteristics, spent brewer’s yeast glucan has high emulsion stability and water-holding capacity fitting best as a fat replacer in different food matrices. Few studies demonstrate the importance and nutritional role of β-glucans from brewer’s yeast, and even less for spent brewer’s yeast, due to additional steps in the extraction process. This review focuses on describing the process of obtaining insoluble β-glucans (particulate) from spent brewer’s yeast and provides an insight into how a by-product from brewing can be converted to potential food applications.

Yarrowia lipolytica N6-glucan protects goat leukocytes against Escherichia coli by enhancing phagocytosis and immune signaling pathway genes

Immunostimulant and protective effects of Yarrowia lipolytica glucans against important pathogens, such as Escherichia coli, have not been investigated in goats and other ruminants. This study aimed to characterize Y. lipolytica N6-glucan (Yl-glucan) and its possible role in immunological signaling pathway activation and immunoprotection against E. coli in goat leukocytes. Characterization analyses showed that Y. lipolytica content had a mix of β and α-D-glucans, molecular weight of 3301.53 kDa and low solubility after the heat treatment. The stimulation of goat leukocytes with Yl-glucan induced protection against E. coli challenge. Remarkably, Yl-glucan and E. coli interaction increased gene expression of dectin-1 and TLR-2 receptors, signaling pathway Syk/NFκB, and cytokines, such as TNF-α and IL-10. As a consequence of signaling activation, phagocytosis, and nitric oxide production enhanced killing of pathogens. Altogether, Y. lipolytica-glucan demonstrated to possess an immunoprotective potential against E. coli through innate immune response modulation in goat leukocytes.

Ferumoxytol-β-glucan Inhibits Melanoma Growth via Interacting with Dectin-1 to Polarize Macrophages into M1 Phenotype

Background: Regulating the polarization of macrophages to antitumor M1 macrophages is a promising strategy for overcoming the immunosuppression of the tumor microenvironment for cancer therapy. Ferumoxytol (FMT) can not only serve as a drug deliver agent but also exerts anti-tumor activity. β-glucan has immuno-modulating properties to prevent tumor growth. Thus, a nanocomposite of FMT surface-coated with β-glucan (FMT-β-glucan) was prepared to explore its effect on tumor suppression. Methods: Male B16F10 melanoma mouse model was established to explore the antitumor effect of FMT-β-glucan. The viability and apoptotic rates of B16F10 cells were detected by cell counting kit-8 and Annexin-V/PI experiments. The levels of M1 markers were quantified by quantitative reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay. Phagocytic activity and intracellular reactive oxygen species (ROS) in macrophages were evaluated by the neutral red uptake assay and flow cytometry, respectively. Small interfering RNA (siRNA) transfection was applied to knock down the Dectin-1 gene in RAW 264.7 cells. Results: FMT-β-glucan suppressed tumor growth to a greater extent and induced higher infiltration of M1 macrophages than the combination of FMT and β-glucan (FMT+β-glucan) in vivo. In vitro, supernatant from FMT-β-glucan-treated RAW 264.7 cells led to lower cell viability and induced more apoptosis of B16F10 cells than that from the FMT+β-glucan group. Moreover, FMT-β-glucan boosted the expression of M1 type markers, and increased phagocytic activity and ROS in RAW 264.7 cells. Further research indicated that FMT-β-glucan treatment promoted the level of Dectin-1 on the surface of RAW 264.7 cells and that knockdown of Dectin-1 abrogated the phosphorylation levels of several components in MAPK and NF-κB signaling. Conclusion: The nanocomposite FMT-β-glucan suppressed melanoma growth by inducing the M1 macrophage-activated tumor microenvironment.

β-Glucan Metabolic and Immunomodulatory Properties and Potential for Clinical Application

β-glucans are complex polysaccharides that are found in several plants and foods, including mushrooms. β-glucans display an array of potentially therapeutic properties. β-glucans have metabolic and gastro-intestinal effects, modulating the gut microbiome, altering lipid and glucose metabolism, reducing cholesterol, leading to their investigation as potential therapies for metabolic syndrome, obesity and diet regulation, gastrointestinal conditions such as irritable bowel, and to reduce cardiovascular and diabetes risk. β-glucans also have immune-modulating effects, leading to their investigation as adjuvant agents for cancers (solid and haematological malignancies), for immune-mediated conditions (e.g., allergic rhinitis, respiratory infections), and to enhance wound healing. The therapeutic potential of β-glucans is evidenced by the fact that two glucan isolates were licensed as drugs in Japan as immune-adjuvant therapy for cancer in 1980. Significant challenges exist to further clinical testing and translation of β-glucans. The diverse range of conditions for which β-glucans are in clinical testing underlines the incomplete understanding of the diverse mechanisms of action of β-glucans, a key knowledge gap. Furthermore, important differences appear to exist in the effects of apparently similar β-glucan preparations, which may be due to differences in sources and extraction procedures, another poorly understood issue. This review will describe the biology, potential mechanisms of action and key therapeutic targets being investigated in clinical trials of β-glucans and identify and discuss the key challenges to successful translation of this intriguing potential therapeutic.

In Vitro Synthesis of Branchless Linear (1 → 6)-α-d-Glucan by Glucosyltransferase K: Mechanical and Swelling Properties of Its Hydrogels Crosslinked with Diglycidyl Ethers

A hydrogel was prepared from a polysaccharide, enzymatically synthesized through a one-pot reaction in aqueous solution, and its properties as a functional material were evaluated. Enzymatic synthesis using glucosyltransferase K obtained from Streptococcus salivarius ATCC 25975 was performed with sucrose as a substrate. The synthetic product was unbranched linear (1 → 6)-α-d-glucan with a high molecular weight, M _w: 1.0-3.0 × 10⁵. The synthesized (1 → 6)-α-d-glucan was insoluble in water and crystallized in a monoclinic unit cell, which is consistent with the hydrated form of dextran. Transparent and highly swellable (1 → 6)-α-d-glucan hydrogels were obtained by crosslinking with diglycidyl ethers. The hydrogels showed no syneresis and no volume change during compression, resulting in the retention of shape under repeated compression. The elastic moduli of these hydrogels (<60 kPa) are smaller than those of other polysaccharide-based hydrogels having the same solid contents. The oven-dried gels could be restored to the hydrogel state with the original transparency and a recovery ratio greater than 98%. The mechanism of water diffusion into the hydrogel was investigated using the kinetic equation of Peppas. The properties of the hydrogel are impressive relative to those of other polysaccharide-based hydrogels, suggesting its potential as a functional biomaterial.

Fungal beta-glucans as adjuvants for treating cancer patients - A systematic review of clinical trials

BACKGROUND & AIMS

Fungal β-glucans have been considered as biological response modifiers (BRMs) promoting stimulation of immune system according to numerous scientific publications performed in vitro and in vivo. Some clinical trials involving such compounds started to be published since 1980's. This systematic review aimed to compile and compare clinical studies using these β-glucans as adjuvants on patients undergoing cancer treatment. Healthy subjects and β-glucans from other sources were excluded.

METHODS

It was developed according to PRISMA-P guidelines (PROSPERO registered n. CRD42020151539), using PICO criteria and the following databases: PubMed, Scielo and LILACS.

RESULTS

We found 1018 articles and after removing duplicated records, select by title/abstract and full-text, only 9 studies remained and 7 more were manually added, totalizing 16 trials involving 1650 patients, with arm sizes varying from 9 until 200 patients. The selected studies (published since 1992-2018) included subjects with diagnosis of 9 types of cancer. The studies used different sources of β-glucans, such as yeast (Saccharomyces cerevisiae), mushrooms (Lentinula edodes and Schizophyllum commune) and non-described fungal sources.

CONCLUSIONS

It was observed that the administration of β-glucan is safe and well-tolerated. Most of the trials pointed that concomitant administration of β-glucan with chemo or radiotherapy reduced the immune depression caused by such treatments and/or accelerated the recovery of white blood cells counts. However, some articles also commented that no statistical difference was encountered between β-glucan treated vs. control groups, which gives a controversial conclusion about the β-glucan effects. The great diversity among the methodology studies and insufficient information was an impeditive for achieving profound statistical analysis, therefore a narrative report of the included studies was performed indicating that further evidences are required to determine the efficacy of this adjuvant in the cancer treatment.

Evaluation of the Cultivated Mushroom Pleurotus ostreatus Basidiocarps Using Vibration Spectroscopy and Chemometrics

Fruiting bodies (basidiocarps) of the cultivated mushroom Pleurotus ostreatus (16 strains) were characterized by vibration spectroscopy and chemometrics. According to organic elemental analysis and Megazyme assay, the basidiocarps contained ~6.2–17.5% protein and ~18.8–58.2% total glucans. The neutral sugar analysis confirmed that glucose predominated in all the samples (~71.3–94.4 mol%). Fourier-transformed (FT) mid- and near-infrared (FT MIR, FT NIR) and FT Raman spectra of the basidiocarps were recorded, and the characteristic bands of proteins, glucans and chitin were assigned. The samples were discriminated based on principal component analysis (PCA) of the spectroscopic data in terms of biopolymeric composition. The partial least squares regression (PLSR) models based on first derivatives of the vibration spectra were obtained for the prediction of the macromolecular components, and the regression coefficients R2 and root mean square errors (RMSE) were calculated for the calibration (cal) of proteins (R2cal 0.981–0.994, RMSEcal ~0.3–0.5) and total glucans (R2cal 0.908–0.996, RMSEcal ~0.6–3.0). According to cross-validation (CV) diagnosis, the protein models were more precise and accurate (R2cv 0.901–0.970, RMSEcv ~0.6–1.1) than the corresponding total glucan models (R2cv 0.370–0.804, RMSEcv ~4.7–8.5) because of the wide structural diversity of these polysaccharides. Otherwise, the Raman band of phenylalanine ring breathing vibration at 1004 cm−1 was used for direct quantification of proteins in P. ostreatus basidiocarps (R ~0.953). This study showed that the combination of vibration spectroscopy with chemometrics is a powerful tool for the evaluation of culinary and medicinal mushrooms, and this approach can be proposed as an alternative to common analytical methods.

Enhancement of exopolysaccharide production from Ganoderma lucidum using a novel submerged volatile co-culture system

Based on the impact of volatile organic compounds (VOCs) on secondary metabolite pathways, a novel submerged volatile co-culture system was constructed, and the effects of thirteen fungal and bacterial VOCs were investigated on Ganoderma lucidum exopolysaccharides production. The results demonstrated at least a 2.2-fold increase in exopolysaccharide (EPS) specific production yield in 6 days submerged volatile co-culture of G. lucidum with Pleurotus ostreatus. Therefore, P. ostreatus was selected as a variable culture, and the effects of agitation speed, inoculum size, initial pH, and co-culture volume on EPSs production were investigated using a Taguchi L₉ orthogonal array. Finally, the highest concentration of EPSs (3.35 ± 0.22 g L^-1) was obtained under optimized conditions; initial pH 5.0, inoculum size 10%, 150 rpm, and 3:1 volume ratio of variable culture to main culture.

The Structural Characteristics and Biological Activities of Intracellular Polysaccharide Derived from Mutagenic Sanghuangporous sanghuang Strain

Sanghuangporous sanghuang is a rare medicinal fungus which contains polysaccharide as the main active substance and was used to treat gynecological diseases in ancient China. The intracellular polysaccharide yield of S. sanghuang was enhanced by the strain A130 which was screened from mutant strains via atmospheric and room temperature plasma (ARTP) mutagenesis. The objective of this research was to investigate the effects of ARTP mutagenesis on structural characteristics and biological activities of intracellular polysaccharides from S. sanghuang. Six intracellular polysaccharide components were obtained from S. sanghuang mycelia cultivated by the mutagenic strain (A130) and original strain (SH1), respectively. The results revealed that the yields of polysaccharide fractions A130-20, A130-50 and A130-70 isolated from the mutagenic strain fermentation mycelia were significantly higher than those of the original ones by 1.5-, 1.3- and 1.2-fold, and the clear physicochemical differences were found in polysaccharide fractions precipitated by 20% ethanol. A130-20 showed a relatively expanded branching chain with higher molecular weight and better in vitro macrophage activation activities and the IL-6, IL-1, and TNF-α production activities of macrophages were improved by stimulation of A130-20 from the mutagenic strain. This study demonstrates that ARTP is a novel and powerful tool to breed a high polysaccharide yield strain of S. sanghuang and may, therefore, contribute to the large-scale utilization of rare medicinal fungi.

Alginate-Derived Elicitors Enhance β-Glucan Content and Antioxidant Activities in Culinary and Medicinal Mushroom, Sparassis latifolia

This study aimed to investigate the elicitation effects of alginate oligosaccharides extracted from brown algae (Sargassum species) on β-glucan production in cauliflower mushroom (Sparassis latifolia). Sodium alginate was refined from Sargassum fulvellum, S. fusiforme, and S. horneri, and characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR), resulting mannuronic acid to guluronic acid (M/G) rationes from 0.64 to 1.38. Three oligosaccharide fractions, ethanol fraction (EF), solid fraction (SF), and liquid fraction (LF), were prepared by acid hydrolysis and analyzed by Fourier transform infrared (FT-IR) spectra and high-performance anion-exchange chromatography with a pulsed amperometric detector (HPAEC-PAD). The samples of S. fusiforme resulted in the highest hydrolysate in SF and the lowest in LF, which was consistent with its highest M/G ratio. The SF of S. fusiforme and LF of S. horneri were chosen for elicitation on S. latifolia, yielding the highest β-glucan contents of 56.01 ± 3.45% and 59.74 ± 4.49% in the stalk, respectively. Total polyphenol content (TPC) and antioxidant activities (2,2’-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging and Superoxide dismutase (SOD)-like activity) of aqueous extracts of S. latifolia were greatly stimulated by alginate elicitation. These results demonstrate that alginate oligosaccharides extracted from brown algae may be useful as an elicitor to enhance the nutritional value of mushrooms.

Simultaneous Nanoscale Imaging of Chemical and Architectural Heterogeneity on Yeast Cell Wall Particles

Particles extracted from yeast cell walls are naturally occurring immunomodulators with significant therapeutic applications. Their biological function has been thought to be a consequence of the overall chemical composition. In contrast, here we achieve direct nanoscale visualization of the compositional and structural heterogeneity of yeast cell wall particles and demonstrate that such nanoscale heterogeneity directly influences the receptor function of immune cells. By combining peak force infrared (PFIR) microscopy with super-resolution fluorescence microscopy, we achieve simultaneous chemical, topographical, and mechanical mapping of cell wall particles extracted from the yeast Saccharomyces cerevisiae with ≈6 nm resolution. We show that polysaccharides (β-glucan and chitin) and proteins are organized in specific nonuniform structures, and their heterogeneous spatial organization leads to heterogeneous recruitment of receptors on immune cell membranes. Our findings indicate that the biological function of yeast cell wall particles depends on not only their overall composition but also the nanoscale distribution of the different cell wall components.

The FT-IR and Raman Spectroscopies as Tools for Biofilm Characterization Created by Cariogenic Streptococci

Fourier transform infrared (FT-IR) and Raman spectroscopy and mapping were applied to the analysis of biofilms produced by bacteria of the genus Streptococcus. Bacterial biofilm, also called dental plaque, is the main cause of periodontal disease and tooth decay. It consists of a complex microbial community embedded in an extracellular matrix composed of highly hydrated extracellular polymeric substances and is a combination of salivary and bacterial proteins, lipids, polysaccharides, nucleic acids, and inorganic ions. This study confirms the value of Raman and FT-IR spectroscopies in biology, medicine, and pharmacy as effective tools for bacterial product characterization.

Unified Strategy toward Stereocontrolled Assembly of Various Glucans Based on Bimodal Glycosyl Donors

Polymers of glucose, the most abundant and one of the biologically important natural products, named glucans are widely present in fungi, bacteria, mammals, and plants with various anomeric configurations and glycosidic linkages. Because of their structural diversity, the unified strategy for the assembly of pure glucans is yet to be developed. Herein, we describe a general strategy that is applicable to construction of all types of glucans by exploiting a bimodal glycosyl donor equipped with C2-o-TsNHbenzyl ether (TAB), which enables stereocontrolled synthesis of both α- and β-glycosides by switching reaction conditions.