Rheologically interesting polysaccharides from yeasts

We have examined the relationships between primary, secondary, and tertiary structures of polysaccharides exhibiting the rheological property of friction (drag) reduction in turbulent flows. We found an example of an exopolysaccharide from the yeastCryptococcus laurentii that possessed high molecular weight but exhibited lower than expected drag reducing activity. Earlier correlations by Hoyt (8,10) showing that β1 → 3, β→4, and αl → 3 linkages in polysaccharides favored drag reduction were expanded to include correlations to secondary structure. The effect of sidechains in a series of gellan gums was shown to be related to sidechain length and position. Disruption of secondary structure in drag reducing polysaccharides reduced drag reducing activity for some but not all exopolysaccharides. The polymer fromC. laurentii was shown to be more stable than xanthan gum and other exopolysaccharides under the most vigorous of denaturing conditions. We also showed a direct relationship between extensional viscosity measurements and the drag reducing coefficient for four exopolysaccharides.

     

High performance liquid chromatographic strategy for the analysis of exopolysaccharides extracted from pathogenic bacteria.

A high performance liquid chromatographic (HPLC) method has been developed to permit the rapid comparison of acidic polysaccharides of diverse compositions and the sensitive determination of their constituents. It is based on two combined analyses of the polysaccharide hydrolysates--a separation of the released compounds by ion-moderated partition chromatography with UV detection at two wavelengths and a separation of the sugar dansylhydrazine derivatives by reversed phase chromatography. The former permits identification and quantitation of uronic and carboxylic acids, the latter permits more sensitive and specific determination of the neutral aldoses. Some bacterial exopolysaccharides have been used to demonstrate the validity of this HPLC procedure for the chemical characterization of uronic acid-containing polysaccharides. This method appears to be useful for studying capsular polysaccharides, which are involved in the evasion of phagocytosis by pathogenic bacteria.     

Characterization of exopolysaccharides in marine colloids by capillary electrophoresis with indirect UV detection

A method was established using capillary electrophoresis with indirect UV detection for analysis of monosaccharides liberated from exopolysaccharides by acidic hydrolysis. Tangential flow filtration was used to isolate high molecular weight polysaccharides from seawater. The capillary electrophoresis method included the use of a background electrolyte consisting of 2,6-dimethoxyphenol and cetyltrimethylammonium bromide. Several neutral sugars commonly existing in marine polysaccharides were separated under optimized conditions. The relative standard deviations were between 1.3% and 2.3% for relative migration time and 1.3-2.5% for peak height. Detection limits (at S/N 3) were in the range of 27.2-47.8 μM. The proposed approach was applied to the analysis of hydrolyzed colloidal polysaccharides in seawater collected from the Baltic Sea. Nanomolar levels of liberated monosaccharides in seawater samples can be detected by preconcentration up to 30,000 times.     

Co-Culture of Microalgae, Cyanobacteria, and Macromycetes for Exopolysaccharides Production: Process Preliminary Optimization and Partial Characterization

In this study, the biomass and exopolysaccharides (EPS) production in co-cultures of microalgae/cyanobacteria and macromycetes was evaluated as a technology for producing new polysaccharides for medical and/or industrial application. Based on biomass and EPS productivity of monocultures, two algae and two fungi were selected and cultured in different co-culture arrangements. The hydrosoluble EPS fractions from mono- and co-cultures were characterized by 13C NMR spectroscopy and gas chromatography coupled to mass spectrometry and compared. It was found that co-cultures resulted in the production of an EPS different from those produced by monocultures, showing fungal predominance with microalgal/cyanobacterial traces. Co-cultures conditions were screened (temperature, agitation speed, fungal and microalgae inoculation rate, initial pH, illumination rate, and glucose concentration) in order to achieve maximum biomass and EPS production, resulting in an increase of 33 and 61% in exopolysaccharides and biomass productions, respectively (patent pending).     

Culture pH affects exopolysaccharide production in submerged mycelial culture of Ganoderma lucidum

In submerged culture of Ganoderma lucidum, the pH optimum for cell growth has been shown to be lower than that for exopolysaccharides (EPS) formation. Therefore, in the present study, a two-stage pH-control strategy was employed to maximize the productions of mycelial biomass and EPS. When compared, a batch culture without pH control had a maximum concentration of EPS and endopolysaccharides, which was much lower than those with pH control. Maximum mycelial growth (12.5 g/L) and EPS production (4.7 g/L) were achieved by shifting the controlled pH from 3.0 to 6.0 after day 4. The contrast between the controlled-pH process and uncontrolled pH was marked. By using various two-stage culture processes, it was also observed that culture pH has a significant affect on the yield of product, mycelial morphology, chemical composition, and molecular weight of EPS. A detailed observation of mycelial morphology revealed that the productive morphological form for EPS production was a dispersed pellet (controlled pH shifting from 3.0 to 6.0) rather than a compact pellet with a dense core area (controlled pH 4.5) or a feather-like pellet (controlled pH shifting from 6.0 to 3.0). Three different polysaccharides were obtained from each pH conditions, and their molecular weights and chemical compositions were significantly different.     

The Antiviral Effect of Panax Notoginseng Polysaccharides by Inhibiting PRV Adsorption and Replication In Vitro

Porcine pseudorabies (PR) is an important infectious disease caused by pseudorabies virus (PRV), which poses a major threat to food safety and security. Vaccine immunization has become the main means to prevent and control the disease. However, since 2011, a new PRV variant has caused huge economic losses to the Chinese pig industry. Panax notoginseng polysaccharides have immunomodulatory activity and other functions, but the antiviral effect has not been reported. We studied the anti-PRV activity of Panax notoginseng polysaccharides in vitro. A less cytopathic effect was observed by increasing the concentration of Panax notoginseng polysaccharides. Western blot, TCID₅₀, plaque assay, and IFA revealed that Panax notoginseng polysaccharides could significantly inhibit the infectivity of PRV XJ5 on PK15 cells. In addition, we also found that Panax notoginseng polysaccharides blocked the adsorption and replication of PRV to PK15 cells in a dose-dependent manner. These results show that Panax notoginseng polysaccharides play an antiviral effect mainly by inhibiting virus adsorption and replication in vitro. Therefore, Panax notoginseng polysaccharides may be a potential anti-PRV agent.     

Natural bacterial and plant biomolecules bearing α-<Emphasis Type="SmallCaps">d</Emphasis>-glucuronic acid residues

The structures of bacterial and plant biomolecules bearing α-d-glucuronic acid residues are considered. The bacterial compounds include capsular polysaccharides, lipopolysaccharides, exopolysaccharides, glycolipids, teichoic acids, and other biomolecules. The compounds isolated from plants are related to hemicellulose components, brown algae polysaccharides, fucoidans, as well as to glycoconjugates comprising lipids, terpenes, and polyphenols.     

Fast data preprocessing for chromatographic fingerprints of tomato cell wall polysaccharides using chemometric methods

The variability in the chemistry of cell wall polysaccharides in pericarp tissue of red-ripe tomato fruit (Solanum lycopersicon Mill.) was characterized by chemical methods and enzymatic degradations coupled to high performance anion exchange chromatography (HPAEC) and mass spectrometry analysis. Large fruited line, Levovil (LEV) carrying introgressed chromosome fragments from a cherry tomato line Cervil (CER) on chromosomes 4 (LC4), 9 (LC9), or on chromosomes 1, 2, 4 and 9 (LCX) and containing quantitative trait loci (QTLs) for texture traits, was studied. In order to differentiate cell wall polysaccharide modifications in the tomato fruit collection by multivariate analysis, chromatograms were corrected for baseline drift and shift of the component elution time using an approach derived from image analysis and mathematical morphology. The baseline was first corrected by using a "moving window" approach while the peak-matching method developed was based upon location of peaks as local maxima within a window of a definite size. The fast chromatographic data preprocessing proposed was a prerequisite for the different chemometric treatments, such as variance and principal component analysis applied herein to the analysis. Applied to the tomato collection, the combined enzymatic degradations and HPAEC analyses revealed that the firm LCX and CER genotypes showed a higher proportion of glucuronoxylans and pectic arabinan side chains while the mealy LC9 genotype demonstrated the highest content of pectic galactan side chains. QTLs on tomato chromosomes 1, 2, 4 and 9 contain important genes controlling glucuronoxylan and pectic neutral side chains biosynthesis and/or metabolism.     

Characterization and Antioxidant Activity of Mannans from Saccharomyces cerevisiae with Different Molecular Weight

Polysaccharides were extracted from natural sources with various biological activities, which are strongly influenced by their chemical structure and molecular weight. In this research, mannans polysaccharides were obtained from Saccharomyces cerevisiae by ethanol precipitation. The molecular weight of YM50, YM70, and YM90 mannans was 172.90 kDa, 87.09 kDa, and 54.05 kDa, respectively. Scanning electron microscopy of YM 90 mannans showed a rough surface with numerous cavities, while the surfaces of YM50 and YM70 were relatively smooth. Sepharose CL-6B and FTIR indicated that mannans had the characteristic bands of polysaccharides. The antioxidant activities of polysaccharides were evaluated in vitro using various assays. Mannans showed a good scavenging activity of DPPH radicals which depend on the molecular weight and concentration, and a higher scavenging activity of hydroxyl radical than ferric-reducing power activities. For the three types of mannans, cytotoxicity and hemolytic activity were rarely detected in mice erythrocytes and Caco-2 cells. Those results could contribute to the further application of mannans from Saccharomyces cerevisiae in the food and medicine industry.     

Strukturuntersuchungen an Mannanderivaten

H-NMR investigations using a high resolution 220 MHz spectrometer were performed on methyl, acetyl and benzoyl derivatives of mannan from ivory nuts and Tubera salep, and on the corresponding d-mannopyranose derivatives. With the exception of the C(1) configuration the structure of these polysaccharides may be determined by comparing the coupling constants and chemical shifts of the substituted polysaccharides with those of the corresponding monosaccharide derivatives. The particularly broad signals in the spectra of low as well as high molecular weight acetyl and benzoyl mannans and furthermore, the differences between the chemical shifts of protons in 1,2,3,4,6-penta-O-acetyl-d-mannopyranose and those of the benzoylated mannans, are discussed in terms of relatively small flexibility of the polymer chains or chain segments in solution. In addition studies to determine the type of glycosidic bonds in polysaccharides from a comparison of the δ_H(1)-values of various polyglycan derivatives are reported.     

Probing Helical Hydrophobic Binding Sites in Branched Starch Polysaccharides Using NMR Spectroscopy

Branched starch polysaccharides are capable of binding multiple hydrophobic guests, but their exploitation as multivalent hosts and in functional materials is limited by their structural complexity and diversity. Linear α(1–4)‐linked glucose oligosaccharides are known to bind hydrophobic guests inside left‐handed single helices in solution and the solid state. Here, we describe the development of an amphiphilic probe that binds to linear α(1–4)‐linked glucose oligosaccharides and undergoes a conformational switch upon complexation, which gives rise to dramatic changes in the ¹H NMR spectrum of the probe. We use this probe to explore hydrophobic binding sites in the branched starch polysaccharides amylopectin and β‐limit dextrin. Diffusion‐ordered (DOSY), nuclear Overhauser effect (NOESY) and chemical shift perturbation (HSQC) NMR experiments are utilised to provide evidence that, in aqueous solution, branched polysaccharides bind hydrophobic guests in well‐defined helical binding sites, similar to those reported for complexation by linear oligosaccharides. By examining the binding affinity of the probe to systematically enzymatically degraded polysaccharides, we deduce that the binding sites for hydrophobic guests can be located on internal as well as external branches and that proximal α(1–6)‐linked branch points weaken but do not prevent complexation.     

Effect of Sonication Treatment and Maceration Time in the Extraction of Polysaccharide Compounds during Red Wine Vinification

The application of high-power ultrasounds (US) at 28 kHz to the crushed grapes and the use of different pomace contact times caused changes in the content and composition of monosaccharides and polysaccharides in the musts and wines. These differences were maintained from the moment of pressing (end of maceration) until the end of the alcoholic fermentation. The US increased the content of monosaccharides and polysaccharides in the musts by facilitating their extraction from the solid parts during maceration. The application of medium maceration time (3 days) to sonicated grapes led to an extraction of polysaccharides rich in arabinose and galactose, rhamnogalacturonan type II (RG-II) and mannoproteins (MP), similar to that observed in the control wines made with an extended maceration of 7 days (968.21 vs. 1029.45; 895.04 vs. 1700.50; 356.81 vs. 343.95, respectively). This fact was attributed to a higher extraction in the must during the sonication process and to an important release of pectic polysaccharides during the pressing of the sonicated pomace, which is reported here for the first time. Therefore, the US technology could be useful for increasing the polysaccharide content in the wines or for reducing the maceration time needed to achieve certain levels of wine polysaccharides.     

Determination of alternariol in tomato paste using solid phase extraction and high-performance liquid chromatography with fluorescence detection.

Alternaria spp. produce a wide variety of toxic metabolites with different chemical structures. Tomato products have been considered a likely source of Alternaria toxins in the human diet because Alternaria is an important spoilage mold of tomatoes. A new method for the determination of these mycotoxins in tomato paste, involving solid phase cartridges for extraction before HPLC fluorescence detection with a reversed phase column and isocratic elution, was developed. The method was demonstrated to be linear in the range 5.2-196 ppb of alternariol (AOH) in tomato paste. Good recoveries were obtained for AOH at all levels assayed (minimum 77.2%). The detection limit of the AOH toxin in real samples of tomato paste was low, 1.93 ppb. The precision of the method was demonstrated with a good repeatability (RSD = 2.98%) and reproducibility (RSD = 9.35%).     

Semi-synthesis of unusual chondroitin sulfate polysaccharides containing GlcA(3-O-sulfate) or GlcA(2,3-di-O-sulfate) units

The extraction from natural sources of Chondroitin sulfate (CS), a polysaccharide used for management of osteoarthritis, leads to very complex mixtures. The synthesis of CS by chemical modification of other polysaccharides has seldom been reported due to the intrinsic complexity that arises from fine chemical modifications of the polysaccharide structure. In view of the growing interest in expanding the application of CS to pharmacological fields other than osteoarthritis treatment, we launched a program to find new sources of known or even unprecedented CS polysaccharides. As part of this program, we report herein on an investigation of the use of a cyclic orthoester group to selectively protect the 4,6-diol of N-acetyl-galactosamine residues in chondroitin (obtained from a microbial source), thereby facilitating its transformation into CSs. In particular, three CS polysaccharides were obtained and demonstrated to possess rare or hitherto unprecedented sulfation patterns by 2D NMR spectroscopy characterization. Two of them contained disaccharide subunits characterized by glucuronic acid residues selectively sulfated at position 3 (GlcA(3S)), the biological functions of which are known but have yet to be fully investigated. This first semi-synthetic access to GlcA(3S)-containing CS could greatly expedite such studies, since it can easily furnish considerable amounts of these polysaccharides, which are usually isolated with difficulty and in very low quantity from natural sources.     

Bacterially induced mineralization of calcium carbonate: the role of exopolysaccharides and capsular polysaccharides.

Bacterially induced carbonate mineralization has been proposed as a new method for the restoration of limestones in historic buildings and monuments. We describe here the formation of calcite crystals by extracellular polymeric substances isolated from Bacillus firmus and Bacillus sphaericus. We isolated bacterial outer structures (glycocalix and parietal polymers), such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) and checked for their influence on calcite precipitation. CPS and EPS extracted from both B. firmus and B. sphaericus were able to mediate CaCO3 precipitation in vitro. X-ray microanalysis showed that in all cases the formed crystals were calcite. Scanning electron microscopy showed that the shape of the crystals depended on the fractions utilized. These results suggest the possibility that biochemical composition of CPS or EPS influences the resulting morphology of CaCO3. There were no precipitates in the blank samples. CPS and EPS comprised of proteins and glycoproteins. Positive alcian blue staining also reveals acidic polysaccharides in CPS and EPS fractions. Proteins with molecular masses of 25-40 kDa and 70 kDa in the CPS fraction were highly expressed in the presence of calcium oxalate. This high level of synthesis could be related to the binding of calcium ions and carbonate deposition.     

OKRA(HIBISCUS ESCULENTUS)AND FENUGREEK(TRIGONELLA FOENUM GRACEUM)MUCILAGE:CHARACTERIZATION AND APPLICATION AS FLOCCULANTS FOR TEXTILE EFFLUENT TAEATMENTS

The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum,commonly called Okra and Fenugreek,respectively,as flocculants was described.These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes.Influences of varying polysaccharide concentration,contact time and pH on removal of pollutant from the textile wastewater were investigated.Results showed that polysaccharides (mucilage) obtained from Okra and Fenugreek were capable of removing 90%-94% of SS,30%-44% of TDS and 30%-35% of dye using a very low concentration of polysaccharide.X-ray diffraction (XRD) patterns of solid waste material obtained before and after the treatment with polysaccharides were used as a supportive evidence to explain the mechanism of flocculation.     

OKRA (HIBISCUS ESCULENTUS) AND FENUGREEK (TRIGONELLA FOENUM GRACEUM) MUCILAGE: CHARACTERIZATION AND APPLICATION AS FLOCCULANTS FOR TEXTILE EFFLUENT TREATMENTS

The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum,commonly called Okra and Fenugreek,respectively,as flocculants was described.These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes.Influences of varying polysaccharide concentration,contact time and pH on removal of pollutant from the text...     

Preparation and preliminary characterization of exopolysaccharides by yeast Rhodotorula acheniorum MC

The effects of various carbon and nitrogen sources on the synthesis of exopolysaccharides by Rhodotorula acheniorum MC were studied. The dynamic viscosity of cell-free culture broths during exopolysaccharide synthesis were measured. The highest values for the viscosity (10.14 MPa.s) and crude polysaccharide productivity (6.6 g/L) were obtained in a medium supplied with 5% sucrose. Ammonium sulfate was the most favorable nitrogen source for exopolysaccharide synthesis. The value of pH played a determinant role, and the obligatory condition for exopolysaccharide production was low (pH 1.7-2.0) during the fermentation. The chemical composition and sugar constituents of the crude exopolysaccharides were determined. Mannose was the main monosaccharide component, and its concentration was the highest (69.13%) in the crude exopolysaccharide synthesized in the medium that included 5% sucrose as a carbon source.     

硫酸化氧化锆固体超强酸

硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。     

Automated Solid‐Phase Synthesis of a β‐(1,3)‐Glucan Dodecasaccharide

β‐Glucans are a group of structurally heterogeneous polysaccharides found in bacteria, fungi, algae and plants. β‐(1,3)‐D ‐Glucans have been studied in most detail due to their impact on the immune system of vertebrates. The studies into the immunomodulatory properties of these glucans are typically carried out with isolates that contain a heterogeneous mixture of polysaccharides of different chain lengths and varying degrees of branching. In order to determine the structure–activity relationship of β‐(1,3)‐glucans, access to homogeneous, structurally‐defined samples of these oligosaccharides that are only available through chemical synthesis is required. The syntheses of β‐glucans reported to date rely on the classical solution‐phase approach. We describe the first automated solid‐phase synthesis of a β‐glucan oligosaccharide that was made possible by innovating and optimizing the linker and glycosylating agent combination. A β‐(1,3)‐glucan dodecasaccharide was assembled in 56 h in a stereoselective fashion with an average yield of 88 % per step. This automated approach provides means for the fast and efficient assembly of linker‐functionalized mono‐ to dodecasaccharide β‐(1,3)‐glucans required for biological studies.