NMR spectroscopic structural characterization of a water-soluble β-(1 → 3, 1 → 6)-glucan from Aureobasidium pullulans

RN0D, a galactoglucan from Panax notoginseng flower induces cancer cell death via PINK1/Parkin mitophagy

Metabolic alterations within mitochondria, encompassing processes such as autophagy and energy metabolism, play a pivotal role in facilitating the swift proliferation, invasion, and metastasis of cancer cells. Despite this, there is a scarcity of currently available medications with proven anticancer efficacy through the modulation of mitochondrial dysfunction in a clinical setting. Here, we introduce the structural characteristics of RN0D, a galactoglucan isolated and purified from Panax notoginseng flowers, mainly composed of β-1,4-galactan and β-1,3/1,6-glucan. RN0D demonstrates the capacity to induce mitochondrial impairment in cancer cells, leading to the accumulation of reactive oxygen species, initiation of mitophagy, and reduction in both mitochondrial number and size. This sequence of events ultimately results in the inhibition of mitochondrial and glycolytic bioenergetics, culminating in the demise of cancer cells due to adenosine triphosphate (ATP) deprivation. Notably, the observed bioactivity is attributed to RN0D's direct targeting of Galectin-3, as affirmed by surface plasmon resonance studies. Furthermore, RN0D is identified as an activator of the PTEN-induced kinase 1 (PINK1)/Parkin pathway, ultimately instigating cytotoxic mitophagy in tumor cells. This comprehensive study substantiates the rationale for advancing RN0D as a potentially efficacious anticancer therapeutic.

Glucans and applications in drug delivery

Glucan is a natural polysaccharide widely distributed in cereals and microorganisms that has various biological activities, including immunomodulatory, anti-infective, anti-inflammatory, and antitumor activities. In addition to wide applications in the broad fields of food, healthcare, and biomedicines, glucans hold promising potential as drug delivery carrier materials or ligands. Specifically, glucan microparticles or yeast cell wall particles are naturally enclosed vehicles with an interior cavity that can be exploited to carry and deliver drug payloads. The biological activities and targeting capacities of glucans depend largely on the recognition of glucan moieties by receptors such as dectin-1 and complement receptor 3, which are widely expressed on the cell membranes of mononuclear phagocytes, dendritic cells, neutrophils, and some lymphocytes. This review summarizes the chemical structures, sources, fundamental properties, extraction methods, and applications of these materials, with an emphasis on drug delivery. Glucans are utilized mainly as vaccine adjuvants, targeting ligands and as carrier materials for various drug entities. It is believed that glucans and glucan microparticles may be useful for the delivery of both small-molecule and macromolecular drugs, especially for potential treatment of immune-related diseases.

β-Glucan fragmentation by microfluidization and TNF-α-immunostimulating activity of fragmented β-glucans

Fragmentation of β-glucans secreted by the fungus Ophiocordyceps dipterigena BCC 2073 achieved by microfluidization was investigated. The degree of β-glucan fragmentation was evaluated based on the average number of chain scissions (α). The effects on the α value of experimental variables like solid concentration of the β-glucan suspension, interaction chamber pressure, and number of passes through the microfluidizer were examined. Kinetic studies were conducted using the relationships of the α and suspension viscosity values with the number of passes. Evidence indicated that α increases with the interaction chamber pressure and the number of passes, whereas the solid concentration shows the inverted effect. Kinetic data indicated that the fragmentation rate increases with β-glucan solid concentration and interaction chamber pressure. Furthermore, since β-glucan molecular weight is a key factor determining its biological activity, the effect of β-glucans of different molecular weights produced by fragmentation on tumor necrosis factor (TNF)-α-stimulating activity in THP-1 human macrophage cells was investigated. Evidence suggested that β-glucans have an immunostimulating effect on macrophage function, in the absence of cytotoxic effects. Indeed, β-glucans characterized by a range of molecular weights produced via microfluidization exhibited promise as immunostimulatory agents.

Recent advances in the biosynthesis of fungal glucan structural diversity

Glucans are the most abundant class of macromolecule polymers in fungi, which are commonly found in Ascomycota and Basidiomycota. Fungal glucans are not only essential for cell integrity and function but also crucial for the immense industrial interest in high value applications. They present a variety of structural characteristics at the nanoscale due to the high regulation of genes and the involvement of stochastic processes in synthesis. However, although recent findings have demonstrated the genes of glucans synthesis are relatively conserved across diverse fungi, the formation and organization of diverse glucan structures is still unclear in fungi. Here, we summarize the structural features of fungal glucans and the recent developments in the mechanisms of glucans biosynthesis. Furthermore, we propose the engineering strategies of targeted glucan synthesis and point out the remaining challenges in the synthetic process. Understanding the synthesis process of diverse glucans is necessary for tailoring high value glucan towards specific applications. This engineering strategy contributes to enable the sustainable and efficient production of glucan diversity.

Use of Aureobasidium in a sustainable economy

Aureobasidium is omnipresent and can be isolated from air, water bodies, soil, wood, and other plant materials, as well as inorganic materials such as rocks and marble. A total of 32 species of this fungal genus have been identified at the level of DNA, of which Aureobasidium pullulans is best known. Aureobasidium is of interest for a sustainable economy because it can be used to produce a wide variety of compounds, including enzymes, polysaccharides, and biosurfactants. Moreover, it can be used to promote plant growth and protect wood and crops. To this end, Aureobasidium cells adhere to wood or plants by producing extracellular polysaccharides, thereby forming a biofilm. This biofilm provides a sustainable alternative to petrol-based coatings and toxic chemicals. This and the fact that Aureobasidium biofilms have the potential of self-repair make them a potential engineered living material avant la lettre. KEY POINTS: •Aureobasidium produces products of interest to the industry •Aureobasidium can stimulate plant growth and protect crops •Biofinish of A. pullulans is a sustainable alternative to petrol-based coatings •Aureobasidium biofilms have the potential to function as engineered living materials.

Research on the application of Thelephora ganbajun exopolysaccharides in antioxidant, anti-inflammatory and spot-fading cosmetics

Thelephora ganbajun exopolysaccharides (TGEP) with a "coral-like" branched chain structure (main chain diameter ∼ 80 nm) were prepared by liquid fermentation and fractionated by ion-exchange chromatography. The main fraction (TGEP-2) with the highest in vitro antioxidant capacity was composed of Glc, Man, Gal, GalA, GlcA, Ara, Rha, GlcN, Fuc and Rib in a molar ratio of 465.43:420.43:219.14:188.43:37:35.14:31.43:19.43:11.14:1, with a molecular weight of 1.879 × 104 Da. The sequence of monosaccharide residue release revealed that Gal, Glc and Ara residues were more distributed in the side-branch chains and at their ends, whereas Man and GalA residues were more distributed in the main chains. TGEP-2 contained linear residues (mainly →4)-Glcp-(1 → and →4)-Manp-(1→), branch residues (→3,6)-Glcp-(1→, →4,6)-Glcp-(1 → and →3,6)-Galp-(1→) and terminal residues (Galp-(1→, Manp-(1 → and Glcp-(1→). TGEP-2 consisted of α- and β-glycosidically linked pyranosides, with a triple helical conformation and many long branches. Zebrafish oxidative stress and inflammation models found that TGEP-2 had antioxidant and anti-inflammatory activities. The zebrafish skin black spot assay showed that TGEP-2 inhibited melanin formation. Therefore, extracellular polysaccharides of T. ganbajun have strong application potential in anti-oxidant, anti-inflammatory and skin spot-fading functions cosmetics.

Sophy β-Glucan from the Black Yeast Aureobasidium pullulans Attenuates Salmonella-Induced Intestinal Epithelial Barrier Injury in Caco-2 Cell Monolayers via Exerting Anti-Oxidant and Anti-Inflammatory Properties

The zoonotic pathogens Salmonella spp. infection disrupted intestinal epithelial barrier function and induced local gastroenteritis and systemic inflammation in humans and animals. Sophy β-glucan, a water-soluble β-1,3/1,6-glucan synthesized from the black yeast Aureobasidium pullulans, was reported with immune-regulatory, anti-inflammatory, and anti-infective properties. Here, we investigated the protective role of sophy β-glucan on Salmonella enterica serotype Enteritidis (SE)-challenged Caco-2 cells monolayer and explored underlying action mechanisms. The results showed that pretreatment with sophy β-glucan blocked the adhesion and invasion of SE onto Caco-2 cells along with alleviating SE-induced epithelial barrier injury, as evidenced by increased trans-epithelial electrical resistance, decreased fluorescently-labeled dextran 4 flux permeability, and an enhanced Claudin-4 protein level in the SE-stimulated Caco-2 cell monolayer. Moreover, treatment with β-glucan down-regulated pro-inflammatory factors (IL-1β, IL-8, and TNF-α) while up-regulating anti-inflammatory factors IL-10 at mRNA and protein levels in SE-infected Caco-2 cells. Furthermore, sophy β-glucan strengthened the anti-oxidative capacity of Caco-2 monolayers cells by elevating T-AOC and SOD activity and inhibiting MDA production defending SE. Together, our data showed that sophy β-glucan could prevent intestinal epithelial injury induced by SE, possibly by exerting anti-oxidant and anti-inflammatory properties, and it might be helpful for controlling SE infection.

Preparation and characterization of carboxymethylated Aureobasidium pullulans β-(1 → 3, 1 → 6)-glucan and its in vitro antioxidant activity

Aureobasidium pullulans β-(1 → 3, 1 → 6)-glucan (APG) has a high degree of β-(1 → 6)-glucosyl branching and a regular triple helical structure similar to that of schizophyllan. In this study, APG was carboxymethylated to different degrees of substitution (DS = 0.51, 1.0, and 2.0, denoted CMAPG 1-3, respectively) using a heterogeneous reaction. With increasing DS, the triple-helix structure drastically decreased and converted to a random coil structure in CMAPG 3. Further, aqueous solutions of CMAPG changed from pseudoplastic fluids to perfect Newtonian liquids with increasing DS, indicating that the intra- and intermolecular hydrogen bonds had been cleaved by the substituents to form a random coil structure. In addition, APG and CMAPG solutions exhibited scavenging ability against hydroxyl, organic, and sulfate radicals. It was also found that the carboxymethylation of APG drastically enhanced the organic radical scavenging ability. On the basis of the relationship between the DS and radical scavenging ability of the CMAPG samples, we believe hydroxyl and organic radicals were preferably scavenged by the donation of hydrogen atoms from the glucose rings and the methylene moieties of the carboxymethyl groups, respectively. Considering the obtained results, CMAPG and APG are expected to have applications in pharmaceuticals, functional foods, and cosmetics as antioxidant polysaccharides.

β-(1 → 3)(1 → 6)glucan from Schizophyllum commune 227E.32: High yield production via glucose/xylose co-metabolization

A co-metabolization of xylose and glucose by Schizophyllum commune 227E.32 wild mushroom for exopolysaccharide (EPS) production is presented. Cultivations performed with S. commune 227E.32 at different xylose concentrations demonstrated that the concentration of 50 g·L-1 of xylose achieved the highest EPS production, around 4.46 g·L-1. Scale-up in a stirred tank reactor (STR) was performed. 10 % inoculum showed the highest cost/benefit ratio regarding sugar conversion and EPS production (Y P/S = 0.90 g·g-1), achieving 1.82 g·L-1 of EPS. Isolation, purification, and characterization were conducted with EPS produced in flasks and STR. GC-MS analysis showed glucose as main monosaccharide constituents for both isolates. 13C NMR and HSQC-edited showed that both EPS isolated consisted of a β-D-Glcp (1 → 3) main chain, partially substituted at O-6 with nonreducing β-D-Glcp ends on every third residue, similar to β-D-glucan isolated from S. commune basidiomes known as schizophyllan (SPG). The Mw was determined by GPC to 1.5 × 106 Da (flasks) and 1.1 × 106 Da (STR). AFM topographs revealed a semi-flexible appearance of the β-D-glucan, consistent with the triple helical structures adopted by SPG and overall contour length consistent with a high molar mass.

Structural characterization and in vitro anti-colon cancer activity of a homogeneous polysaccharide from Agaricus bisporus

Colon cancer is the third most prevalent cancer and the second most deadly cancer in the world. Anti-colon cancer activity of Agaricus bisporus polysaccharides has not been studied. In this paper, Agaricus bisporus polysaccharides were sequentially extracted by room temperature water, hot water, high pressure hot water, dilute alkaline solution and concentrated alkaline solution. A homogeneous polysaccharide (WAAP-1) was obtained using DEAE Cellulose-52 column. Physicochemical properties, structural characterization and anti-colon cancer activity of WAAP-1 were investigated. The results showed that WAAP-1 was a neutral polysaccharide with molecular weight of 10.1 kDa. The monosaccharide composition was glucose, mannose and galactose with a molar ratio of 84.95:8.97:4.50. The main chain was mainly composed of (1,4)-α-D-Glcp and (1,6)-β-D-Manp. In vitro anti-colon cancer results showed that WAAP-1 could significantly inhibit proliferation of colon cancer cell HT-29. It promoted apoptosis and inhibited epithelial mesenchymal transition of HT-29 by up-regulating the expression of Caspase-3, Bax and E-cadherin proteins and down-regulating the expression of Bcl-2 and Vimentin proteins. The results provided new potential possibilities for the development of novel functional foods or antitumor drugs.

Quantitative Analysis of The High-Yield Hydrolysis of Kelp by Laminarinase and Alginate Lyase

Kelp is an abundant, farmable biomass-containing laminarin and alginate as major polysaccharides, providing an excellent model substrate to study their deconstruction by simple enzyme mixtures. Our previous study showed strong reactivity of the glycoside hydrolase family 55 during hydrolysis of purified laminarin, raising the question of its reactivity with intact kelp. In this study, we determined that a combination of a single glycoside hydrolase family 55 β-1,3-exoglucanase with a broad-specificity alginate lyase from the polysaccharide lyase family 18 gives efficient hydrolysis of untreated kelp to a mixture of simple sugars, that is, glucose, gentiobiose, mannitol-end glucose, and mannuronic and guluronic acids and their soluble oligomers. Quantitative assignments from nanostructure initiator mass spectrometry (NIMS) and 2D HSQC NMR spectroscopy and analysis of the reaction time-course are provided. The data suggest that binary combinations of enzymes targeted to the unique polysaccharide composition of marine biomass are sufficient to deconstruct kelp into soluble sugars for microbial fermentation.

Pectins from the sea grass Enhalus acoroides (L.f.) Royle: Structure, biological activity and ability to form nanoparticles

Two pectins from the seagrass Enhalus acoroides (L.f.) Royle were isolated for the first time. Their structures and biological activities were investigated. NMR spectroscopy showed one of them to consist exclusively from the repeating →4-α-d-GalpUA→ residue (Ea1), while the other had a much more complex structure that also included 1→3-linked α-d-GalpUA residues, 1→4-linked β-apiose residues and small amounts of galactose and rhamnose (Ea2). The pectin Ea1 showed noticeable dose-dependent immunostimulatory activity, the Ea2 fraction was less effective. Both pectins were used to create pectin-chitosan nanoparticles for the first time, and the influence of pectin/chitosan mass ratio on their size and zeta potential was investigated. Ea1 particles were slightly smaller than Ea2 particles (77 ± 16 nm vs 101 ± 12 nm) and less negatively charged (-23 mV vs -39 mV). Assessment of their thermodynamic parameters showed that only the second pectin could form nanoparticles at room temperature.

Abnormal proliferation of gut mycobiota contributes to the aggravation of Type 2 diabetes

Type 2 diabetes (T2D) constitutes a worldwide health threat, and the underlying mechanism for the development and progression of T2D is complex and multifactorial. During the last decade, gut commensal bacteria have been found to play a crucial role in the regulation of T2D and related metabolic disorders. However, as a considerable component in gut microbiome, the relationship between mycobiota and T2D and related metabolic disorders remains unclear. As a proof-of-concept, we observed that the ablation of the commensal fungi in mice can protect HFD (High fat diet) induced insulin resistance and related metabolic disorders. Both ITS2 (internal transcribed spacer 2) sequencing and culture-dependent analysis show the enrichment of Candida albicans in samples from individuals with T2D (Chinese Clinical Trial Registry, ChiCTR2100042049). Repopulation with C. albicans in HFD mice accelerated insulin resistance and related disorders. Mechanically, we found the β-glucan from C. albicans mirrored the deteriorating effect of C. albicans through the dectin-1 dependent pathway. Our current findings support that gut mycobiota play an important role in the progress of T2D and indicated the preventing of gut mycobiota is a promising strategy to alleviate insulin resistance and related metabolic dysfunctions.

Structure and bioactivity of polysaccharide from a subseafloor strain of Schizophyllum commune 20R-7-F01

Fungal polysaccharide is a kind of biomacromolecule with multiple biological activities, which has a wide application prospect and may play an important role in organisms to cope with extreme environments. Herein, we reported an extracellular polysaccharide (EPS) produced by Schizophyllum commune 20R-7-F01 that was isolated from subseafloor sediments at ~2 km below the seafloor, obtained during expedition 337. The monosaccharide of EPS was glucose and its molecular weight was 608.8 kDa. Methylation and NMR analysis indicated that the backbone of the EPS was (1 → 3)-β-D-glucan with a side chain (1 → 6) β-D-glucan linking at every third residue. Bio-active assays revealed that the EPS had potent antioxidant activity and could promote RAW264.7 cells viability and phagocytosis. These results suggest that fungi derived from sediments below seafloor are important and new source of polysaccharides and may be involved in the adaptation of fungi to anoxic subseafloor extreme ecosystem.

Detailed Structural Characterization of Oxidized Sucrose and Its Application in the Fully Carbohydrate-Based Preparation of a Hydrogel from Carboxymethyl Chitosan

Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed by applying various nuclear magnetic resonance techniques, which permitted the structural and quantitative characterization of the two main OS products, each of which contained four aldehyde groups. In addition, we investigated the use of OS as a cross-linking agent in the preparation of a hydrogel from carboxymethyl chitosan (CMC), one of the most popular polysaccharides for use in biomedical applications. The primary amine groups of CMC were immediately cross-linked with the aldehyde groups of OS to form hydrogels without the requirement for a catalyst. It was found that the degree of cross-linking could be easily controlled by the feed amount of OS during CMC hydrogel preparation and the final cross-linking degree affected the thermal, swelling, and rheological properties of the obtained hydrogel. The results presented in this study are therefore expected to be applicable in the preparation of fully carbohydrate-based hydrogels for medical and pharmaceutical applications.

A Novel Polysaccharide From Heimioporus retisporus Displays Hypoglycemic Activity in a Diabetic Mouse Model

A novel polysaccharide, Heimioporus retisporus Polysaccharide (HRP) was extracted from the edible mushroom Heimioporus retisporus. HRP had weight-average molecular weight 1,949 kDa and number-average molecular weight 873 kDa, and its major components were arabinose (0.71%), galactose (12.93%), glucose (49.00%), xylose (8.59%), mannose (17.78%), and glucuronic acid (10.99%). Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy revealed that HRP was composed of 1,3-linked β-D-glucose, 1,6-linked β-D-mannose, 1,6-linked β-D-galactose, 1,4-linked β-D-galactose, 1,4-linked β-D-xylose, and 1,5-linked α-L-arabinose. Thermogravimetric analysis indicated that degradation temperature (T₀) of HRP was 200°C. In an STZ-induced diabetic mouse model, oral administration of HRP (40 mg/kg/d) for 28 days significantly reduced blood glucose levels, and reduced heart organ index by decreasing expression of IL-6 and TNF-α. Our findings indicate hypoglycemic effect of HRP, and its potential application as a hypoglycemic agent.

Neutral Polysaccharides From Hohenbuehelia serotina With Hypoglycemic Effects in a Type 2 Diabetic Mouse Model

Neutral polysaccharides (NHSPs) from the mushroom Hohenbueheliaserotina were purified by D301/D152 resin ion-exchange chromatography and DEAE-cellulose anion exchange chromatography. The weight-average molecular weight (M_W) and number-average molecular weight (Mn) of NHSP were 1,821 and 820.55 kDa, respectively. A monosaccharide component analysis showed that NHSP was composed of glucose, galactose, and mannose in molar ratio 2.6:2.1:1.0. FT-IR and NMR (¹H and HSQC) spectroscopic analyses revealed that NHSP contained mainly 1,3-linked β-D-glucose, 1,4-linked β-D-glucose, 1,6-linked β-D-mannose, 1,6-linked α-D-mannose, and 1,6-linked β-D-galactose. The thermogravimetric analysis (TGA) showed that NHSP has good thermal stability below 250°C. NHSP notably reduced the blood glucose level (hypoglycemic effect) at dose 200 mg/kg for 21 days in a type 2 diabetic mouse model. NHSP reduced the liver index significantly, suggesting that it may help prevent hepatic steatosis or hepatomegaly.

Downstream processing and structural confirmation of pullulan - A comprehensive review

Pullulan is a microbial polymer, commercially produced from Aureobasidium pullulans. Downstream processing of pullulan involves a multi-stage process which should be efficient, safe and reproducible. In liquid-liquid separations, firstly cell free extract is separated. Cell biomass can be separated after fermentation either by centrifugation or filtration. Due to practically insolubility of pullulan in organic solvents, ethanol and isopropanol are the most commonly used organic solvents for its recovery. Pullulan can also be purified by chromatographic techniques, but these are not cost effective for the purification of pullulan. Efficient aqueous two-phase system can be used for the purification of pullulan. The current review describes the methods and perspectives used for solid-liquid separation, liquid-liquid separations and finishing steps for the recovery of pullulan. Techniques used to determine the structural attributes of pullulan have also been highlighted.

Structural characterization of polysaccharide purified from Hericium erinaceus fermented mycelium and its pharmacological basis for application in Alzheimer's disease: Oxidative stress related calcium homeostasis

The purified polysaccharides from Hericium erinaceus fermented mycelium entitled with PHEB was analyzed and it was mainly composed of six glycosidic bonds. It has been confirmed to show the relieving activity against Alzheimer's Disease (AD)- just as behaviors of B6C3-Tg (APPswePSEN1d E9)/Nju double transgenic [Genotype: (Appswe)T, (Psen1) T] (APP/PS1) mice. Six-week PHEB administration significantly improved the cognitive behavior of mice. Brain injury, amyloid beta deposition and tau hyperphosphorylation were alleviated in PHEB-treated AD mice without changes in other tissues. PHEB alleviated the oxidative stress in brains of AD mice via regulation the Nrf2 and its downstream kinase, which further improved the cholinergic system function. Proteomics and bioinformatics analysis showed that the therapeutic effect of PHEB is achieved by regulating calcium homeostasis mediated by oxidative stress. Furthermore, PHEB regulated the CaMK II/IV to achieve the calcium homeostasis in brains; and ultimately to show the anti-AD property.

pH-Sensitive branched β-glucan-modified liposomes for activation of antigen presenting cells and induction of antitumor immunity

Induction of cellular immunity is important for effective cancer immunotherapy. Although various antigen carriers for cancer immunotherapy have been developed to date, balancing efficient antigen delivery to antigen presenting cells (APCs) and their activation via innate immune receptors, both of which are crucially important for the induction of strong cellular immunity, remains challenging. For this study, branched β-glucan was selected as an intrinsically immunity-stimulating and biocompatible material. It was engineered to develop multifunctional liposomal cancer vaccines capable of efficient interactions with APCs and subsequent activation of the cells. Hydroxy groups of branched β-glucan (Aquaβ) were modified with 3-methylglutaric acid ester and decyl groups, respectively, to provide pH-sensitivity and anchoring capability to the liposomal membrane. The modification efficiency of Aquaβ derivatives to the liposomes was significantly high compared with linear β-glucan (curdlan) derivatives. Aquaβ derivative-modified liposomes released their contents in response to weakly acidic pH. As a model antigenic protein, ovalbumin (OVA)-loaded liposomes modified with Aquaβ derivatives interacted efficiently with dendritic cells, and induced inflammatory cytokine secretion from the cells. Subcutaneous administration of Aquaβ derivative-modified liposomes suppressed the growth of the E.G7-OVA tumor significantly compared with curdlan derivative-modified liposomes. Aquaβ derivative-modified liposomes induced the increase of CD8⁺ T cells, and polarized macrophages to the antitumor M1-phenotype within the tumor microenvironment. Therefore, pH-sensitive Aquaβ derivatives can be promising materials for liposomal antigen delivery systems to induce antitumor immune responses efficiently.

Improved production of β-glucan by a T-DNA-based mutant of Aureobasidium pullulans

To improve β-1,3-1,6-D-glucan (β-glucan) production by Aureobasidium pullulans, an Agrobacterium tumefaciens-mediated transformation method was developed to screen a mutant A. pullulans CGMCC 19650. Based on thermal asymmetric-interlaced PCR detection, DNA sequencing, BLAST analysis, and quantitative real-time PCR assay, the T-DNA was identified to be inserted in the coding region of mal31 gene, which encodes a sugar transporter involved in pullulan biosynthesis in the mutant. The maximal biomass and β-glucan production under batch fermentation were significantly increased by 47.6% and 78.6%, respectively, while pullulan production was decreased by 41.7% in the mutant, as compared to the parental strain A. pullulans CCTCC M 2012259. Analysis of the physiological mechanism of these changes revealed that mal31 gene disruption increased the transcriptional levels of pgm2, ugp, fks1, and kre6 genes; increased the amounts of key enzymes associated with UDPG and β-glucan biosynthesis; and improved intracellular UDPG contents and energy supply, all of which favored β-glucan production. However, the T-DNA insertion decreased the transcriptional levels of ags2 genes, and reduced the biosynthetic capability to form pullulan, resulting in the decrease in pullulan production. This study not only provides an effective approach for improved β-glucan production by A. pullulans, but also presents an accurate and useful gene for metabolic engineering of the producer for efficient polysaccharide production. KEY POINTS: • A mutant A. pullulans CGMCC 19650 was screened by using the ATMT method. • The mal31 gene encoding a sugar transporter was disrupted in the mutant. • β-Glucan produced by the mutant was significantly improved.

A review of NMR analysis in polysaccharide structure and conformation: Progress, challenge and perspective

Nuclear magnetic resonance (NMR) has been widely used as an analytical chemistry technique to investigate the molecular structure and conformation of polysaccharides. Combined with 1D spectra, chemical shifts and coupling constants in both homo- and heteronuclear 2D NMR spectra are able to infer the linkage and sequence of sugar residues. Besides, NMR has also been applied in conformation, quantitative analysis, cell wall in situ, degradation, polysaccharide mixture interaction analysis, as well as carbohydrates impurities profiling. This review summarizes the principle and development of NMR in polysaccharides analysis, and provides NMR spectra data collections of some common polysaccharides. It will help to promote the application of NMR in complex polysaccharides of biochemical interest, and provide valuable information on commercial polysaccharide products.

Structure of a laminarin-type β-(1→3)-glucan from brown algae Sargassum henslowianum and its potential on regulating gut microbiota

A homogeneous polysaccharide named SHNP with apparent molecular weight of 8.4 kDa was purified from brown algae Sargassum henslowianum using ethanol precipitation, ion-exchange chromatography, and gel-filtration column chromatography. Structural analyses reveal that SHNP is completely composed of glucose, and its backbone consists of β-D-(1→3)-Glcp with side chains comprising t-β-D-Glcp attached at the O-6 position. Thus, SHNP is a laminarin-type polysaccharide. In vitro fermentation test results showed that SHNP was digested by gut microbiota; the pH value in the fecal culture of SHNP was significantly decreased; and total short-chain fatty acids, acetic, propionic and n-butyric acids were significantly increased. Furthermore, SHNP regulated the intestinal microbiota composition by stimulating the growth of species belonging to Enterobacteriaceae while depleting Haemophilus parainfluenzae and Gemmiger formicilis. Taken together, these results indicate that SHNP has the potential for regulating gut microbiota, but its specific role in the regulation requires to be further investigated.

Possibility of Japanese Cedar Pollen Causing False Positives in the Deep Mycosis Test

Because Japanese cedar pollen (JCP) contains beta-1,3-d-glucan (BG), there is concern that its lingering presence in the atmosphere, especially during its scattering period, may cause false positives in the factor-G-based Limulus amebocyte lysate (LAL) assay used to test for deep mycosis (i.e., G-test). Hence, we examined whether the LAL assay would react positively with substances contained in JCP by using the G-test to measure JCP particles and extracts. BG was purified from the JCP extract on a BG-specific affinity column, and the percentage extractability was measured using three different BG-specific quantitative methods. The G-test detected 0.4 pg BG in a single JCP particle and 10 fg from a single particle in the extract. The percentage extractability of JCP-derived BG was not significantly different among the three quantitative methods. As the JCP particles should technically have been removed during serum separation, they should be less likely to be a direct false-positive factor. However, given that the LAL-assay-positive substances in the JCP extract were not distinguishable by the three BG-specific quantitative methods, we conclude that they may cause the background to rise. Therefore, in Japan false positives arising from JCP contamination should be considered when testing patients for deep mycosis.

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.

Interaction Between Dendritic Cells and Candida krusei β-Glucan Partially Depends on Dectin-1 and It Promotes High IL-10 Production by T Cells

Host-Candida interaction has been broadly studied during Candida albicans infection, with a progressive shift in focus toward non-albicans Candida species. C. krusei is an emerging multidrug resistant pathogen causing rising morbidity and mortality worldwide. Therefore, understanding the interplay between the host immune system and C. krusei is critically important. Candia cell wall β-glucans play significant roles in the induction of host protective immune responses. However, it remains unclear how C. krusei β-glucan impacts dendritic cell (DC) responses. In this study, we investigated DC maturation and function in response to β-glucans isolated from the cell walls of C. albicans, C. tropicalis, and C. krusei. These three distinct Candida β-glucans had differential effects on expression of the DC marker, CD11c, and on DC maturation. Furthermore, bone-marrow derived DCs (BMDCs) showed enhanced cytokine responses characterized by substantial interleukin (IL)-10 production following C. krusei β-glucan stimulation. BMDCs stimulated with C. krusei β-glucan augmented IL-10 production by T cells in tandem with increased IL-10 production by BMDCs. Inhibition of dectin-1 ligation demonstrated that the interactions between dectin-1 on DCs and cell wall β-glucans varied depending on the Candida species. The effects of C. krusei β-glucan were partially dependent on dectin-1, and this dependence, in part, led to distinct DC responses. Our study provides new insights into immune regulation by C. krusei cell wall components. These data may be of use in the development of new clinical approaches for treatment of patients with C. krusei infection.

Oligo-DNA Stoichiometrically Binds β-1,3-Glucan with the Best Fit Length

Oligo-deoxyadenylic acid (dA_X) forms a novel 1:2 triple-helix with β-1,3-d-glucan schizophyllan (SPG). We found that dA_X meticulously selects the most suitable length of SPG to bind; for example, dA₃₀ only complexes with a short SPG chain having 30, 60, or 90 main-chain glucoses, and they can be easily isolated with each other. This study demonstrated such a novel stoichiometric complex formation by using gel permeation chromatography coupled with multi-angle light scattering and synchrotron small-angle X-ray scattering. These oligo-DNA/polysaccharide complexes can be used as a tool for delivering therapeutic oligonucleotides to immunocytes that express the β-1,3-d-glucan receptors. The present study provides a robust platform technique to characterize them in terms of modern regulatory science of nanomedicines, which is requisite to transfer drug candidates into clinical trial. Our findings are important for characterizing these complexes as well as for providing a new insight into nucleotide and saccharide chemistry.

Single-stranded β-1,3-1,6-glucan as a carrier for improved dissolution and membrane permeation of poorly water-soluble compounds

The ability of a water-soluble, single-stranded β-1,3/1,6-glucan (ssβ-glucan), recovered by hydrothermal treatment, to enhance the solubility and membrane permeability of poorly water-soluble compounds was examined. As a poorly water-soluble model compound, quercetin (QUE) was used. The aqueous solubility of spray-dried particles (SDPs) of QUE/ssβ-glucan was significantly enhanced compared with that of the untreated QUE powder and the physical mixture of QUE/ssβ-glucan. Fourier-transform infrared spectra and small-angle X-ray scattering suggested strong interactions between ssβ-glucan and QUE in the SDPs, which was attributable to QUE entrapment in the helical ssβ-glucan structure. The amount of QUE infused into Caco-2 cells from QUE/ssβ-glucan SDPs was 16-fold and 5-fold higher than the amount infused from untreated QUE powder and the physical mixture of QUE/ssβ-glucan, respectively. These results showed that water-soluble ssβ-glucan improved QUE dissolution and membrane permeability.

Evaluation of Polish wild Mushrooms as Beta-Glucan Sources

Mushroom beta-glucans show immunomodulatory, anticancer and antioxidant features. Numerous papers have been published in the last years on fungal polysaccharides, especially beta-glucans, demonstrating their various biological activities. However substantial data about beta-glucan contents in many mushroom species, especially wild mushrooms, are still missing. Therefore, the main objective of the study was to evaluate β-glucans in 18 species of wild mushrooms and three species of commercial mushrooms for comparison purposes. The contents of β-glucans were determined by the Megazyme method and with the Congo red method, which differ in analytical procedure. Among wild mushrooms, the highest mean β-glucan content assessed with the Megazyme method was found in Tricholoma portentosum (34.97 g/100 g DM), whereas with the Congo red method in Lactarius deliciosus (17.11 g/100 g DM) and Suillus grevillei (16.97 g/100 g DM). The β-glucans in wild mushrooms assessed with the Megazyme method were comparable to commercial mushrooms, whereas β-glucans assessed with the Congo red method were generally higher in wild mushrooms, especially in Russula vinosa, L. deliciosus and S. grevillei. This study indicates wild mushrooms as interesting material for β-glucan extraction for food industry and medicinal purposes.

Marine Microalgae Biomolecules and Their Adhesion Capacity to Salmonella enterica sv. Typhimurium

Different molecules have been tested as analog receptors due to their capacity to bind bacteria and prevent cell adhesion. By using in vitro assays, the present study characterized the aqueous and alkaline extracts from microalgae Pavlova lutheri and Pavlova gyrans and evaluated the capacity of these extracts to adhere to enterobacteria (Salmonella Typhimurium). The aqueous and alkaline extracts of both species were fractionated via freeze-thawing, giving rise to soluble and insoluble (precipitate) fractions in cold water. The obtained fractions were studied using thermogravimetric, methylation analyses, and using 1D and 2D NMR techniques. The cold-water-soluble fractions obtained from the aqueous extracts were mainly composed of highly branched (1→3),(1→6)-β-glucans, whereas the cold-water-precipitate fractions were constituted by (1→3)-β-glucans. The alkaline extract fractions showed similar compositions with a high protein content, and the presence of glycosides (sulfoquinovosylglycerol (SQG), digalactosylglycerol (DGG)), and free fatty acids. The linear (1→3)-β-glucans and the alkaline extract fractions showed an adhesion capacity toward Salmonella. The chemical composition of the active fractions suggested that the presence of three-linked β-glucose units, as well as microalgal proteins and glycosides, could be important in the adhesion process. Therefore, these microalgal species possess a high potential to serve as a source of anti-adhesive compounds.

Solid-state relaxation NMR dataset for a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans and schizophyllan from Schizophyllum commune

We report the solid-state nuclear magnetic resonance (NMR) relaxation dataset for a triple helix and a random structure of water-soluble Aureobasidium pullulans β-(1→3, 1→6)-d-glucan (APG) and those of schizophyllan from Schizophyllum commune (SPG), obtained by the Bruker BioSpin 500 MHz NMR spectrometer. These data include solid-state proton spin-lattice relaxation in the rotating frame (T_1ρH) and ¹³C spin-lattice relaxation (T_1C) of these two β-(1→3, 1→6)-glucans, which are related to the subject of article in International Journal of Biological Macromolecules, entitled “Characterization of the secondary structure and order–disorder transition of a β-(1→3, 1→6)-glucan from Aureobasidium pullulans” [1]. Data can help to investigate the structural characterization of the structural polysaccharides.

Diversity and Antimicrobial Activity of Culturable Fungal Endophytes in Solanum mauritianum

Plant endophytes are microbial sources of bioactive secondary metabolites, which mimic the natural compounds chemistry of their respective host plants in a similar manner. This study explored the isolation and identification of fungal endophytes, and investigated the antibacterial and antimycobacterial activity of their crude extracts. Fungal endophytes were isolated from Solanum mauritianum, identified using morphological traits and internal transcribed spacer ribosomal-deoxyribonucleic acid (ITS-rDNA) sequence analysis. Eight fungal endophytes were identified as Aureobasidium pullulans, Paracamarosporium leucadendri, Cladosporium sp., Collectotrichum boninense, Fusarium sp., Hyalodendriella sp., and Talaromyces sp., while Penicillium chrysogenum was isolated from the leaves and unripe fruits. Good activity was observed for the crude extracts of Paracamarosporium leucadendri inhibiting Mycobacterium bovis, Klebsiella pneumoniae, and Pseudomonas aeruginosa at 6 µg/mL. Crude extracts of Fusarium sp., showed activity at 9 μg/mL against M. bovis, M. smegmatis and K. pneumonia. In general, the crude extracts showed great activity against Gram-negative and Gram-positive bacteria and novel results for two mycobacteria species M. bovis and M. smegmatis. The results provide evidence of diverse fungal endophytes isolated from Solanum mauritianum, and evidence that fungal endophytes are a good source of bioactive compounds with pharmaceutical potential, particularly against Mycobacterium tuberculosis.

Natural polysaccharides with different conformations: extraction, structure and anti-tumor activity

Natural polysaccharides as sustainable polymers are rich sources with good biological safety and various biological functions, which are important research topics in the fields of food and medicine.

Structural Characterization and Chain Conformation of Water-Soluble β-Glucan from Wild Cordyceps sinensis

Water-soluble β-d-glucan was obtained from wild Cordyceps sinensis by alkali solution and ethanol precipitation. The structure characteristics were determined using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD), methylation combined with gas chromatography-mass spectrometry, and one-/two-dimensional nuclear magnetic resonance spectroscopy. Results showed that β-d-glucan had a structure of every seven (1→3)-β-d-Glcp backbone residues with two (1→6)-β-d-Glcp branches. Additionally, conformation properties in different solvents were investigated by static light scattering, dynamic light scattering, and HPSEC with multiple detectors. It was found that β-d-glucan in 0.5 M NaOH had a narrow unimodal distribution of hydrodynamic radius displaying a spherical coil conformation, whereas it formed severe aggregation in dimethyl sulfoxide. In 0.1 M NaNO₃, β-d-glucan mainly existed as a rod-like conformation corresponding to a helical structure together with small aggregates (10%). This work added more information to the understanding of C. sinensis polysaccharides.

Characterization of the secondary structure and order-disorder transition of a β-(1 → 3, 1 → 6)-glucan from Aureobasidium pullulans

This study revealed the secondary structures of the water-soluble Aureobasidium pullulans β-(1 → 3, 1 → 6)-d-glucan (APG) whose primary structural unit is a β-(1 → 3)-d-glucan backbone with four β-(1 → 6)-d-glucosyl branching units every six residues. Solid-state NMR spectroscopy, X-ray diffractometry (XRD), and small-angle X-ray scattering (SAXS) experiments involving samples prepared from lyophilized APG showed that APG forms a triple helix in H₂O and a random structure in DMSO. In addition, it was revealed that the transformation from the triple helix of APG to the random structure occurs reversibly, and that the triple helix is recovered from the random structure in DMSO/H₂O mixtures containing more than 30% H₂O. Solid-state NMR and diffraction studies revealed that the triple helix of APG is more stable than that of schizophyllan (SPG) whose structure comprises a β-(1 → 3)-d-glucan backbone with one β-(1 → 6)-d-branching unit every three residues. The APG helical pitch is 1.82 nm, which is about 10% longer than that of the triple helix of SPG. These findings show that the β-(1 → 6) side-chain frequency strongly affects the stability and helical pitch of a β-(1 → 3, 1 → 6)-d-glucan.

Agar Extraction By-Products from Gelidium sesquipedale as a Source of Glycerol-Galactosides

Alkaline treatment is a common step largely used in the industrial extraction of agar, a phycocolloid obtained from red algae such as Gelidium sesquipedale. The subsequent residue constitutes a poorly valorized by-product. The present study aimed to identify low-molecular-weight compounds in this alkaline waste. A fractionation process was designed in order to obtain the oligosaccharidic fraction from which several glycerol-galactosides were isolated. A combination of electrospray ion (ESI)-mass spectrometry, ¹H-NMR spectroscopy, and glycosidic linkage analyses by GC-MS allowed the identification of floridoside, corresponding to Gal-glycerol, along with oligogalactosides, i.e., (Gal)_2⁻4-glycerol, among which α-d-galactopyranosyl-(1→3)-β-d-galactopyranosylα1-2⁻glycerol and α-d-galactopyranosyl-(1→4)-β-d-galactopyranosylα1-2⁻glycerol were described for the first time in red algae.

Two-dimensional NMR data of a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans and schizophyllan from Schizophyllum commune

This article contains two-dimensional (2D) NMR experimental data, obtained by the Bruker BioSpin 500 MHz NMR spectrometer (Germany) which can used for the determination of primary structures of schizophyllan from Schizophyllum commune (SPG) and a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans. Data include analyzed the 2D NMR spectra of these β-glucans, which are related to the subject of an article in Carbohydrate Polymers, entitled “NMR spectroscopic structural characterization of a water-soluble β-(1→3, 1→6)-glucan from A. pullulans” (Kono et al., 2017) [1]. Data can help to assign the ¹H and ¹³C chemical shifts of the structurally complex polysaccharides.