Effect of Intake of Food Hydrocolloids of Bacterial Origin on the Glycemic Response in Humans: Systematic Review and Narrative Synthesis.

Diabetes mellitus is a chronic condition characterized by increased blood glucose levels from dysfunctional carbohydrate metabolism. Dietary intervention can help to prevent and manage the disease. Food hydrocolloids have been shown to have favorable properties in relation to glycaemic regulation. However, the use of food hydrocolloids of bacterial origin to modulate glucose responses is much less explored than other types of hydrocolloids. We, therefore, carried out the first review examining the impact of intake of food hydrocolloids of bacterial origin (as a direct supplement or incorporated into foods) on glycemic response in humans. Fourteen studies met the inclusion criteria. They used either xanthan gum, pullulan, or dextran as interventions. There was a wide variation in the amount of hydrocolloid supplementation provided and methods of preparation. Postprandial blood glucose responses were reduced in half of the studies, particularly at higher intake levels and longer chain hydrocolloids. When xanthan gum was added to the cooking process of muffins and rice, a significant reduction in postprandial blood glucose was observed. The use of these hydrocolloids is potentially effective though more research is needed in this area.

Rheological and emulsifying properties of an exopolysaccharide produced by potential probiotic Leuconostoc citreum-BMS strain.

EPS-BMS, is to our knowledge, the first high molecular weight exopolysaccharide from potential probiotic Leuconostoc citreum-BMS strain that consists on a mixture of α-(1,6)-dextran branched at the third position and ß-(2,6)-levan. This sample exhibited interesting rheological and emulsifying properties under different conditions. Steady shear experiments proved that EPS-BMS had a pseudoplastic behavior without thixotropic properties. Interestingly, pseudoplasticity was maintained even under stress conditions of temperature, pH and salts, which could provide some sensory properties for food products such as mouth feel. Dynamic oscillatory measurements reflected a liquid-like behavior of the sample regardless of the studied EPS concentration, pH, temperature and ionic force. Results related to the emulsifying as well as interfacial properties showed that EPS-BMS had great potential to be applied as emulsifier and/or emulsion stabilizer in both neutral and acidic conditions. Based on the properties reported in this work, EPS-BMS could be potentially applied in the food industry.

Novel amphiphilic dextran esters with antimicrobial activity.

New amphiphilic dextran esters were obtained by polysaccharide functionalization with different substituted 1,2,3-triazoles-4-carboxylic acid via in situ activation with N, N'-carbonyldiimidazole. Nitrogen-containing heterocyclic derivatives were achieved by copper(I)-catalyzed cycloaddition reaction between organic azides and ethyl propiolate. Structural characteristics of the compounds were studied by elemental analysis, Fourier transform infrared and nuclear magnetic resonance spectroscopy (1H and 13C-NMR). Thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction were used for esters characterization. Properties of polymeric self-associates, formed in aqueous solution, were studied by dynamic light scattering and transmission electron microscopy. The critical aggregation concentration values for dextran esters, determined by fluorescence spectroscopy, were in the range of 4.1-9.5 mg/dL. Antimicrobial activity, investigated for some of the polymers by disc-diffusion method, pointed out that polysaccharide esters were active.

Isolation and characterization of dextran produced by Lactobacillus sakei L3 from Hubei sausage.

An exopolysaccharide (EPS)-producing bacterial strain L3 was isolated from Hubei sausage and identified as Lactobacillus sakei via morphological, physiological, biochemical and 16S rDNA analysis. FT-IR spectroscopy and NMR revealed that L3 EPS was a dextran containing d-glucose residues with α-1,6 glycosidic linkage. Rheological studies showed that it had high viscosity at high concentration, low temperature, and acidic pH (pH 3.0). Scanning electron microscopy of the L3 dextran demonstrated a porous and branched morphology, and atomic force microscopy showed lumps of varying height on the rough surface of the L3 EPS polymer. The EPS was thermally stable up to 272°C and could coagulate sucrose-supplemented milk. Together, these results suggested that L3 EPS might have potential applications in food processing and other areas.

A novel strategy to utilize ethylene glycol-ionic liquids for the selective precipitation of polysaccharides.

In the present work, three hydrophilic ionic liquids based on the combination between imidazolium cations attached with ethylene glycol polymers of various lengths and hexafluorophosphate anion were designed and synthesized for the separation of polysaccharides. By employing dextran 100 kDa as model compound, the effects of ionic liquid content, solvent/anti-solvent volume, and temperature on its recovery efficiency were investigated systematically. The ability of these ionic liquids to precipitate dextran 100 kDa, increases with the elongation of ethylene glycol polymer chain. The established ionic liquid-based precipitation system was successfully applied to selectively precipitate polysaccharides from water extracts of three traditional Chinese medicines and the precipitation could be achieved in about 15 min. In addition, the different precipitation responses of acidic, neutral, and basic polysaccharides in the ionic liquid-based precipitation system and theoretical calculations both suggested that the selective precipitation of polysaccharides was probably mediated by interaction between ionic liquids and polysaccharides. The proposed strategy facilitated the isolation and purification of polysaccharides and may trigger a novel application of ionic liquids in carbohydrate research.

Extraction and characterization of dextran from Leuconostoc pseudomesenteroides YB-2 isolated from mango juice.

An exopolysaccharide (EPS)-producing strain of YB-2 isolated from mango juice was identified as Leuconostoc pseudomesenteroides. The molecular weight (Mw) of this EPS was 7.67×105 Da. Gas chromatography (GC) analysis confirmed the presence of only glucose monomers. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectra displayed the glucan nature of the EPS with 96.8% α-(1→6) and 3.2% branching α-(1→3) linkages. Scanning electron microscopy (SEM) showed smooth surfaces and compact structure. The water solubility index (WSI) and water-holding capacity (WHC) of dextran were 97.48±2.46% and 287.51±7.93%, respectively. The rheological analysis of dextran elucidated a non-Newtonian pseudoplastic behavior. The dextran revealed an inhibitory activity against Escherichia coli and Staphylococcus aureus with minimal inhibitory concentrations (MIC) of 2.0 mg/mL and 3.0 mg/mL, respectively.

Effects of Plasma Proteins on the Transport and Surface Characteristics of Polysulfone/Polyethersulfone and Asymmetric Cellulose Triacetate High Flux Dialyzers.

Blood-membrane interactions can have a large impact on the performance of hemodialysis membranes, particularly for high flux membranes in which the membrane itself provides very low resistance to solute transport. The objective of this study was to examine the effects of exposure to serum on the solute clearance and convective sieving characteristics of high flux polysulfone (Optiflux F250NR), polyethersulfone (ELISIO-25H), and asymmetric cellulose triacetate (SOLACEA-25H) hemodialyzers using both vitamin B12 and a range of polydisperse dextrans. Zeta potential measurements were used to obtain additional insights into the changes in membrane surface properties. Exposure to serum in a simulated dialysis session caused a significant reduction in both solute clearance and sieving coefficients for the polysulfone/polyethersulfone dialyzers, particularly for the larger molecular weight solutes. In contrast, the transport characteristics of the asymmetric cellulose triacetate dialyzers were almost unchanged after exposure to serum. The zeta potential of the cellulose triacetate membrane became slightly more negative after exposure to serum, consistent with an adsorbed protein layer composed largely of albumin. The net result is that the asymmetric cellulose triacetate dialyzer had dramatically higher clearance of the larger dextrans after exposure to serum, with the clearance and sieving coefficient for a 10 kDa molecular weight dextran being more than an order of magnitude greater than that of the polysulfone/polyethersulfone membranes. These results provide important insights into the expected clinical performance of these high flux dialyzers.

Amorphous-Amorphous Phase Separation of Freeze-Concentrated Protein and Amino Acid Excipients for Lyophilized Formulations.

The objective of this study was to elucidate the mixing state of proteins and amino acid excipients concentrated in the amorphous non-ice region of frozen solutions. Thermal analysis of frozen aqueous solutions was performed in heating scans before and after a heat treatment. Frozen aqueous solutions containing a protein (e.g., recombinant human albumin, gelatin) or a polysaccharide (dextran) and an amino acid excipient (e.g., L-arginine, L-arginine hydrochloride, L-arginine monophosphate, sodium L-glutamate) at varied mass ratios showed single or double Tg' (glass transition temperature of maximally freeze-concentrated solutes). Some mixture frozen solutions rich in the polymers maintained the single Tg' of the freeze-concentrated amorphous solute-mixture phase. In contrast, amino acid-rich mixture frozen solutions revealed two Tg's that suggested transition of concentrated non-crystalline solute-mixture phase and excipient-dominant phase. Post-freeze heat treatment induced splitting of the Tg' in some intermediate mass ratio mixture solutions. The mixing state of proteins and amino acids varied depending on their structure, salt types, mass ratio, composition of co-solutes (e.g., NaCl) and thermal history. Information on the varied mixing states should be valuable for the rational use of amino acid excipients in lyophilized protein pharmaceuticals.

Molar mass fractionation in aqueous two-phase polymer solutions of dextran and poly(ethylene glycol).

Dextran and poly(ethylene glycol) (PEG) in phase separated aqueous two-phase systems (ATPSs) of these two polymers, with a broad molar mass distribution for dextran and a narrow molar mass distribution for PEG, were separated and quantified by gel permeation chromatography (GPC). Tie lines constructed by GPC method are in excellent agreement with those established by the previously reported approach based on density measurements of the phases. The fractionation of dextran during phase separation of ATPS leads to the redistribution of dextran of different chain lengths between the two phases. The degree of fractionation for dextran decays exponentially as a function of chain length. The average separation parameters, for both dextran and PEG, show a crossover from mean field behavior to Ising model behavior, as the critical point is approached.

Impregnation of cotton fabric with silver nanoparticles synthesized by dextran isolated from bacterial species Leuconostoc mesenteroides T3.

This study was aimed to highlight the possibility of cotton fabric impregnation with silver nanoparticles synthesized by dextran isolated from Leuconostoc mesenteroides T3 in order to obtain antimicrobial properties. The fabrication of dextran was proved by FTIR spectroscopy. Particle sizes of synthesized dextran and silver nanoparticles were measured by dynamic light scattering method. The presence of silver nanoparticles on the surface of cotton fabric was confirmed by scanning electron microscopy, X-ray diffraction measurements and reflectance spectrophotometry. Antimicrobial activity of cotton fabric impregnated with silver nanoparticles was tested against bacteria Escherichia coli and Staphylococcus aureus, and fungus Candida albicans. The results indicated that synthesized silver nanoparticles can provide satisfactory antimicrobial activity. However, maximum reduction (99.9%) of all tested microorganisms can be obtained only when 1.0mmolL(-1) colloid consisting of silver nanoparticles is applied.

Chemical Functionalization of Germanium with Dextran Brushes for Immobilization of Proteins Revealed by Attenuated Total Reflection Fourier Transform Infrared Difference Spectroscopy.

Protein immobilization studied by attenuated total reflection Fourier transform infrared (ATR-FT-IR) difference spectroscopy is an emerging field enabling the study of proteins at atomic detail. Gold or glass surfaces are frequently used for protein immobilization. Here, we present an alternative method for protein immobilization on germanium. Because of its high refractive index and broad spectral window germanium is the best material for ATR-FT-IR spectroscopy of thin layers. So far, this technique was mainly used for protein monolayers, which lead to a limited signal-to-noise ratio. Further, undesired protein-protein interactions can occur in a dense layer. Here, the germanium surface was functionalized with thiols and stepwise a dextran brush was generated. Each step was monitored by ATR-FT-IR spectroscopy. We compared a 70 kDa dextran with a 500 kDa dextran regarding the binding properties. All surfaces were characterized by atomic force microscopy, revealing thicknesses between 40 and 110 nm. To analyze the capability of our system we utilized N-Ras on mono-NTA (nitrilotriacetic acid) functionalized dextran, and the amount of immobilized Ras corresponded to several monolayers. The protein stability and loading capacity was further improved by means of tris-NTA for immobilization. Small-molecule-induced changes were revealed with an over 3 times higher signal-to-noise ratio compared to monolayers. This improvement may allow the observation of very small and so far hidden changes in proteins upon stimulus. Furthermore, we immobilized green fluorescent protein (GFP) and mCherry simultaneously enabling an analysis of the surface by fluorescence microscopy. The absence of a Förster resonance energy transfer (FRET) signal demonstrated a large protein-protein distance, indicating an even distribution of the protein within the dextran.

Dextrans produced by lactic acid bacteria exhibit antiviral and immunomodulatory activity against salmonid viruses.

Viral infections in the aquaculture of salmonids can lead to high mortality and substantial economic losses. Thus, there is industrial interest in new molecules active against these viruses. Here we describe the production, purification, and the physicochemical and structural characterization of high molecular weight dextrans synthesized by Lactobacillus sakei MN1 and Leuconostoc mesenteroides RTF10. The purified dextrans, and commercial dextrans with molecular weights ranging from 10 to 2000kDa, were assayed in infected BF-2 and EPC fish cell-line monolayers for antiviral activity. Only T2000 and dextrans from MN1 and RTF10 had significant antiviral activity. This was similar to results obtained against infectious pancreatic necrosis virus. However the dextran from MN1 showed ten-fold higher activity against hematopoietic necrosis virus than T2000. In vivo assays using the MN1 polymer confirmed the in vitro results and revealed immunomodulatory activity. These results together with the high levels of dextran production (2gL(-1)) by Lb. sakei MN1, indicate the compounds potential utility as an antiviral agent in aquaculture.

Structural and biocompatibility properties of dextran from Weissella cibaria JAG8 as food additive.

Dextran produced from Weissella cibaria JAG8 was purified and characterized. The molecular mass of dextran as determined by the gel filtration and copper bicinchoninate method was approximately, 800 kDa. Monosaccharide analysis revealed that the polysaccharide comprised only glucose units. Dynamic light scattering study confirmed the mono-disperse nature of dextran with hydrodynamic radius of 900 nm. Surface morphology study of dextran by scanning electron microscopy showed the porous web like structure. Cytotoxicity studies on human cervical cancer (HeLa) cell line showed non-toxic and biocompatible nature of dextran. The relative browning for dextran from W. cibaria JAG8 was similar to commercial prebiotic Nutraflora P-95 and 3-fold lower than Raftilose P-95. Synthesis of dextran by dextransucrase treated, sucrose-supplemented skimmed milk revealed the promising potential of dextran as a food additive.

Challenges in analysis of high-molar mass dextrans: comparison of HPSEC, AsFlFFF and DOSY NMR spectroscopy.

Dilute solutions of various dextran standards, a high-molar mass (HMM) commercial dextran from Leuconostoc spp., and HMM dextrans isolated from Weissella confusa and Leuconostoc citreum were analyzed with high-performance size-exclusion chromatography (HPSEC), asymmetric flow field-flow fractionation (AsFlFFF), and diffusion-ordered NMR spectroscopy (DOSY). HPSEC analyses were performed in aqueous and dimethyl sulfoxide (DMSO) solutions, while only aqueous solutions were utilized in AsFlFFF and DOSY. The study showed that all methods were applicable to dextran analysis, but differences between the aqueous and DMSO-based solutions were obtained for HMM samples. These differences were attributed to the presence of aggregates in aqueous solution that were less prevalent in DMSO. The study showed that DOSY provides an estimate of the size of HMM dextrans, though calibration standards may be required for each experimental set-up. To our knowledge, this is the first study utilizing these three methods in analyzing HMM dextrans.

Structural analysis and characterization of dextran produced by wild and mutant strains of Leuconostoc mesenteroides.

An exopolysaccharide known as dextran was produced by Leuconostoc mesenteroides KIBGE-IB22 (wild) and L. mesenteroides KIBGE-IB22M20 (mutant). The structure was characterized using FTIR, (1)H NMR, (13)C NMR and 2D NMR spectroscopic techniques, whereas surface morphology was analyzed using SEM. A clear difference in the spectral chemical shift patterns was observed in both samples. All the spectral data indicated that the exopolysaccharide produced by KIBGE-IB22 is a mixture of two biopolymers. One was dextran in α-(1 → 6) configuration with a small proportion of α-(1 → 3) branching and the other was levan containing ß-(2 → 6) fructan fructofuranosyl linkages. However, remarkably the mutant only produced dextran without any concomitant production of levan. Study suggested that the property of KIBGE-IB22M20, regarding improved production of high molecular weight dextran in a shorter period of fermentation time without any contamination of other exopolysaccharide, could be employed to make the downstream process more feasible and cost effective on large scale.

Passivated aluminum nanohole arrays for label-free biosensing applications.

We report the fabrication and performance of a surface plasmon resonance aluminum nanohole array refractometric biosensor. An aluminum surface passivation treatment based on oxygen plasma is developed in order to circumvent the undesired effects of oxidation and corrosion usually found in aluminum-based biosensors. Immersion tests in deionized water and device simulations are used to evaluate the effectiveness of the passivation process. A label-free bioassay based on biotin analysis through biotin-functionalized dextran-lipase conjugates immobilized on the biosensor-passivated surface in aqueous media is performed as a proof of concept to demonstrate the suitability of these nanostructured aluminum films for biosensing.

Novel dextran from Pediococcus pentosaceus CRAG3 isolated from fermented cucumber with anti-cancer properties.

The porous branched dextran of molecular mass 2.93 × 10(5) Da with 50% overall yield (4.5mg/ml) was produced from Pediococcus pentosaceus CRAG3 (GenBank ID: JX679020), a novel isolate from fermented cucumber. It contained glucose monomers linked through 75% α-(1,6) linkage with 25% (α-1,3) branching as displayed by spectroscopic analysis. The peak analysis showed α-(1,3) branching after every five glucose units of main chain. In vitro cytotoxicity analysis of dextran displayed anti-cancer activity against cervical cancer (HeLa) and colon cancer (HT29) cell lines opening new horizons in its pharmaceutical applications. Dextran showed enhanced growth of macrophage lines revealing its biocompatible nature.

Separation and characterization of dextran extracted from deteriorated sugarcane.

In this research work, dextran was extracted from deteriorated sugarcane by alcohol precipitation and purified by gel filtration chromatography. Total acid hydrolysis and enzymatic degradation were utilized to confirm the purity of separated polysaccharide. Using the more recently available techniques such as ((1)H,(13)C) and two-dimensional (COSY and HMQC) NMR spectral analysis, methylation GC-MS and MALDI-TOF mass spectrometry, the structure of sugarcane dextran (SC-Dex) was investigated. On the basis of all spectra, SC-Dex showed a branched polysaccharide that contained only d-glucose residues in consecutive α-(1-6) linkages in the main chain with α-(1-3) branches. Methylation analysis showed that, the degree of α-(1-3) branching levels was 4.37%. Several structural fragments were identified from MALDI-TOF spectrum with peak-to-peak mass difference of 162gmol(-1), which confirmed that the repeat unit in SC-Dex was d-glucose. The surface morphology of SC-Dex, revealed the spherically shaped and porous structure. Using HPSEC-MALLS-RI system, the average molecular weight of SC-Dex was estimated to be 1.753×10(6)gmol(-1) with an index of polydispersity value of 1.069.

A novel high dextran yielding Weissella cibaria JAG8 for cereal food application.

A new isolate from apple (Malus domestica) producing dextransucrase and dextran was characterized by morphological, biochemical and 16S rDNA analyses. The bacterium that was identified as Weissella cibaria (GenBank accession number KC110687) was Gram positive, non-motile, short rod, catalase negative, vancomycin resistant. The maximum dextransucrase activity (5.8 U/ml) as well as dextran concentration of 38 mg/ml was observed at 24°C after 12 h of growth under static condition. The polyethylene glycol (PEG)-400 fractionation of partially purified enzyme showed a specific activity of 20.0 U/mg and displayed a single homogenous band of molecular size 177 kDa on sodium dodecyl sulphate-Poly acrylamide gel electrophoresis (SDS-PAGE) (7.5%). The dextran was enzymatically synthesized using dextransucrase and substrate sucrose. Dextran was purified by alcohol precipitation for further characterization. The rheological analysis of dextran elucidated a non-Newtonian pseudoplastic behaviour. (1)H and (13)C NMR analyses revealed the fact that the dextran contained d-glucose monomer with 93.0% of α(1 â†’ 6) linear and 7.0% of α(1 â†’ 3) branched linkages.

[Chemical constituents of Pilea cavaleriei subsp. cavaleriei].

OBJECTIVE: To investigate chemical constituents from folk herb Pilea cavaleriei subsp. cavaleriei. METHOD: The compounds were separated and purified by silica gel, Sephadex LH-20 and the like. The structures were identified by spectral methods such as (1)H, (13)C-NMR and MS. RESULT: Seventeen compounds were isolated and identified as benzoic acid (1), 4-hydroxy benzalde-hyde (2), coumaric acid(3), protocatechuic acid (4), gallic acid (5), 4-hydroxy benzoic acid (6), 3-indole carboxaldehyde (7), 3-indole carbo-xylicacid (8), 4-methyl-(1,2,3) -triazole(9), uracil(10), nicotinamide (11), (2S,E)-N-[2-hydroxy-2-(4-hydroxy phenyl) ethyl] ferulamide (12), (+) -dehydrovomifoliol (13), hentriantane (14), beta-sitosterol (15), palmitic acid (16), daucossterol (17) , respectively. CONCLUSION: All compounds were obtained from the genus for the first time.