Production and Properties of Two Novel Exopolysaccharides Synthesized by a Thermophilic Bacterium Aeribacillus pallidus 418

Synthesis of innovative exocellular polysaccharides (EPSs) was reported for few thermophilic microorganisms as one of the mechanisms for surviving at high temperature. Thermophilic aerobic spore-forming bacteria able to produce exopolysaccharides were isolated from hydrothermal springs in Bulgaria. They were referred to four species, such as Aeribacillus pallidus, Geobacillus toebii, Brevibacillus thermoruber, and Anoxybacillus kestanbolensis. The highest production was established for the strain 418, whose phylogenetic and phenotypic properties referred it to the species A. pallidus. Maltose and NH₄Cl were observed to be correspondingly the best carbon and nitrogen sources and production yield was increased more than twofold in the process of culture condition optimization. After purification of the polymer fraction, a presence of two different EPSs, electroneutral EPS 1 and negatively charged EPS 2, in a relative weight ratio 3:2.2 was established. They were heteropolysaccharides consisting of unusual high variety of sugars (six for EPS 1 and seven for EPS 2). Six of the sugars were common for both EPSs. The main sugar in EPS 1 was mannose (69.3 %); smaller quantities of glucose (11.2 %), galactosamine (6.3 %), glucosamine (5.4 %), galactose (4.7 %), and ribose (2.9 %) were also identified. The main sugar in EPS 2 was also mannose (33.9 %), followed by galactose (17.9 %), glucose (15.5 %), galactosamine (11.7 %), glucosamine (8.1 %), ribose (5.3 %), and arabinose (4.9 %). Both polymers showed high molecular weight and high thermostability.     

Characterization of hyperbranched glycopolymers produced in vitro using enzymes

Asymmetrical flow field flow fractionation (AF4) has proven to be a very powerful and quantitative method for the determination of the macromolecular structure of high molar mass branched biopolymers, when coupled with multi-angle laser light scattering (MALLS). This work describes a detailed investigation of the macromolecular structure of native glycogens and hyperbranched α-glucans (HBPs), with average molar mass ranging from 2?×?10⁶ to 4.3?×?10⁷ g mol^?1, which are not well fractionated by means of classical size-exclusion chromatography. HBPs were enzymatically produced from sucrose by the tandem action of an amylosucrase and a branching enzyme mimicking in vitro the elongation and branching steps involved in glycogen biosynthesis. Size and molar mass distributions were studied by AF4, coupled with online quasi-elastic light scattering (QELS) and transmission electron microscopy. AF4-MALLS-QELS has shown a remarkable agreement between hydrodynamic radii obtained by online QELS and by AF4 theory in normal mode with constant cross flow. Molar mass, size, and dispersity were shown to significantly increase with initial sucrose concentration, and to decrease when the branching enzyme activity increases. Several populations with different size range were observed: the amount of small size molecules decreasing with increasing sucrose concentration. The spherical and dense global conformation thus highlighted was partly similar to native glycogens. A more detailed study of HBPs synthesized from low and high initial sucrose concentrations was performed using complementary enzymatic hydrolysis of external chains and chromatography. It emphasized a more homogeneous branching pattern than native glycogens with a denser core and shorter external chains.

Liposomal structure: A comparative study on light scattering and chromatography techniques

Liposomes play an important role in medical and pharmaceutical science as, nanoscale drug carriers. One of the most important features is their size and size distribution, influencing both their bio-distribution and their targeting efficiency to tumors and also therapeutic activity of liposomal antitumor drugs. In this study, the effect of preparation method and molecular interaction on size and shape of liposome was studied. The size and shape characterization of liposomes was performed by asymmetrical flow field-flow fractionation coupled online with multi-angle light scattering (AF4-MALS). The size distributions obtained by AF4-MALS were compared to mean particle sizes and size distribution measured with other standard method such as Photon Correlation Spectroscopy (PCS). Furthermore, the effect of molecular interaction (hydrophilic and hydrophobic model drugs) on liposomal structure was assessed.     

Co(III) ammine electroreduction reactions as kinetic probes of double layer structure: The reduction of fluoropentaammine cobalt(III) at varying ionic strengths

The electroreduction rate of fluoropentaammine cobalt(III) was studied in a variety of single electrolytes of varying ionic strengths at the mercury-aqueous interface in order to assess the experimental double layer effects in the presence of anion specific adsorption in comparison with the predictions of the coupled Gouy-Chapman-Stern-Frumkin (GCSF) theory. The net charge densities in the inner layer region determined from the experimental rate data using the GCSF model were usually in good agreement with the corresponding literature values that were determined from equilibrium double layer data over a range of ionic strengths (μ=0.01 to 1.0 M) and electrode charge densities (q^m～0–15μC cm^?2) in NaF, KPF₆, KCl, NaN₃, KNO₃ and NaClO₄ electrolytes. Large discrepancies between these kinetic and equilibrium results were observed in concentrated Na₂SO₄ electrolytes which were ascribed to the effects of ion-pairing between Co(NH₃)₅F²⁺ and SO₄^2?. The relative success of the simple GCSF model for this and other Co(III) ammine reduction reactions is compared and contrasted with the corresponding behavior of other electrode reactions that have been studied previously, and possible reasons for the behavioral simplicity of the present systems are suggested. The suitability of Co(III) ammine electroreduction reactions as kinetic probes of the double layer structure at solid electrode-aqueous interfaces is noted.     

Asymmetrical flow field-flow fractionation with multi-angle light scattering detection for the analysis of structured nanoparticles

Synthesis and applications of new functional nanoparticles are topics of increasing interest in many fields of nanotechnology. Chemical modifications of inorganic nanoparticles are often necessary to improve their features as spectroscopic tracers or chemical sensors, and to increase water solubility and biocompatibility for applications in nano-biotechnology. Analysis and characterization of structured nanoparticles are then key steps for their synthesis optimization and final quality control. Many properties of structured nanoparticles are size-dependent. Particle size distribution analysis then provides fundamental analytical information. Asymmetrical flow field-flow fractionation (AF4) with multi-angle light scattering (MALS) detection is able to size-separate and to characterize nanosized analytes in dispersion. In this work we focus on the central role of AF4-MALS to analyze and characterize different types of structured nanoparticles that are finding increasing applications in nano-biotechnology and nanomedicine: polymer-coated gold nanoparticles, fluorescent silica nanoparticles, and quantum dots. AF4 not only size-fractionated these nanoparticles and measured their hydrodynamic radius (r_h) distribution but it also separated them from the unbound, relatively low-M_r components of the nanoparticle structures which were still present in the sample solution. On-line MALS detection on real-time gave the gyration radius (r_g) distribution of the fractionated nanoparticles. Additional information on nanoparticle morphology was then obtained from the r_h/r_g index. Stability of the nanoparticle dispersions was finally investigated. Aggregation of the fluorescent silica nanoparticles was found to depend on the concentration at which they were dispersed. Partial release of the polymeric coating from water-soluble QDs was found when shear stress was induced by increasing flowrates during fractionation.     

Characterization of oat proteins and aggregates using asymmetric flow field-flow fractionation

The soluble proteins and protein aggregates in Belinda oats were characterized using asymmetric flow field-flow fractionation (AF4) coupled with online UV–vis spectroscopy and multiangle light-scattering detection (MALS). Fractions from the AF4 separation were collected and further characterized by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The AF4 fractogram of the oat extracts revealed three peaks which were determined to be monomeric forms of soluble proteins, globulin aggregates, and β-glucan, respectively. The early eluting monomeric proteins ranged in molar mass (MM) between 5 and 90 kg/mol and in hydrodynamic diameter (D _h) from 1.6 to 13 nm. The MM at peak maximum of the globulin aggregate peak was found to be ～300 kg/mol and the D _h was measured to be ～20 nm. SDS-PAGE of the collected fraction across this peak revealed two bands with MM of 37 and 27 kg/mol which correspond to the α and β subunits of globulin indicating the elution of globulin aggregates. A third peak at long retention time was determined to be β-glucan through treatment of the oat extract with β-glucanase and by injection of β-glucan standards. The amount of soluble protein was measured to be 83.1?±?2.3 wt.%, and the amount of albumin proteins was measured to be 17.6?±?5.7 wt.% of the total protein in the oats. The results for Belinda oat extracts show that the AF4-MALS/UV platform is capable of characterizing the physicochemical properties such as MM and hydrodynamic size distribution of proteins and protein aggregates within a complicated food matrix environment and without the need to generate protein isolates.

Complex formation of zinc, cadmium and manganese(II) with 2-hydroxypropylene-1,3-diamine-N,N,N′,N′-tetraacetic acid

The stability constants of the complexes of 2-hydroxypropylene-1,3-diamine N,N,N′,N′-tetraacetic acid (H₄L) with Zn²⁺, Cd²⁺, and Mn²⁺ ions were determined by the potentiometric method on the background of KCl at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0. The resulting data were extrapolated to the zero ionic strength by a one-parameter equation.     

Molybdenum(VI) complexation by amino-acids. Part 1 Species in aqueous solution of sodium molybdate and L-aspartate

Summary The complexation of molybdenum(VI) by L-aspartate in dilute aqueous solutions, at pH 6, was studied using u.v. spectrophotometry,¹H and¹³C n.m.r. spectroscopy. A single complex anion, [MoO₃(C₄H₅NO₄)]^2–, is observed in solution. The conformation of the aspartate ion in the complex was determined and shown to be consistent with it acting as a terdentate ligand. The formation constant of the complex was determined at different ionic strengths. Job's method has been employed, here and elsewhere, to study the stoichiometry of the complex. However, the result is strongly affected by polymerization of molybdenum(VI): this effect is discussed.     

Optimization of medium by orthogonal matrix method for submerged mycelial culture and exopolysaccharide production in Collybia maculata

Optimization of submerged culture conditions for the production of mycelial growth and exopolysaccharides (EPSs) by Collybia maculata was investigated. The optimum temperature and the initial pH for EPS production in a shake-flask culture of C. maculata were found to be 20°C and 5.5, respectively. Among the various medium’s constituents examined, glucose, Martone A-1, K₂HPO₄, and CaCl₂ were the most suitable carbon, nitrogen, and mineral sources for EPS production, respectively. The optimum concentration of the medium’s ingredients determined using the orthogonal matrix method was as follows: 30 g/L of glucose, 20 g/L of Martone A-1, 1g/L of K₂HPO₄, and 1g/L of CaCl₂. Under the optimized culture conditions, the maximum concentration of EPSs in a 5-L stirred-tank reactor was 2.4 g/L, which was approximately five times higher than that in the basal medium. A comparative fermentation result showed that the EPS productivity in an airlift reactor was higher than that in the stirred-tank reactor despite the lower mycelial growth rate. The specific productivities and the yield coefficients in the airlift reactor were higher than those in the stirred-tank reactor even though the volumetric productivities were higher in the stirred-tank reactor than in the airlift reactor.     

Thermodynamics (Solubility and Protonation Constants) of Risedronic Acid in Different Media and Temperatures (283.15–318.15 K)

Potentiometric measurements were carried out to study the protonation constants of risedronic acid (RA) in NaCl_(aq), (CH₃)₄NCl_(aq) and (C₂H₅)₄NI_(aq) at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15). In the same conditions, solubility measurements were also performed. Calorimetric measurements were done in NaCl to determine the protonation enthalpy values at I = 0.15 mol·dm^?3 and 298.15 K. Generally, the proton binding process was endothermic and the driving force was entropic in nature. The values of the protonation constants determined in NaCl_(aq) are lower than those obtained in the two tetraalkylammonium salts. The medium effect was interpreted using different thermodynamic models in terms of variation of the activity coefficients with ionic strength (Debye–Hückel type and SIT), or formation of weak complexes between risedronate (Ris^4?) and the ions of the supporting electrolytes. Specific interaction coefficients (ε) and the stability of five (CH₃)₄N⁺/Ris^4? (at different temperatures and ionic strengths) species are reported. The total solubility of risedronic acid is higher in NaCl_(aq) than in the other two ionic media and, in all cases, increases with increasing temperature. Setschenow and activity coefficients of the neutral species were also computed in all ionic media.     

Behavior of extracellular polymers and bio-fouling during hydrogen fermentation with a membrane bioreactor

The characteristics of membrane fouling were investigated by examining the behaviors of extracellular polymer substances (EPSs) produced by hydrogen-producing bacteria during hydrogen fermentation from a submerged membrane bioreactor (MBR). The MBR consisted of a 1.4-L submerged membrane filtration tank and 3-L hydrogen fermenter. An intermittent suction operation was selected to maintain stable filtration performance. The operation of the suction pump was alternately shifted to ON for 7 min followed by OFF for 3 min, with bio-gas sparging at a flow rate of 5.0 L/m²/h (LMH), and manually regulated. Most of the EPS during the continuous hydrogen fermentation using an MBR had accumulated in the reactor because they were retained by the membrane by adsorption onto the polymeric membrane surface. The amount of proteins in the EPS extracted was increased to 179 mg/L and that of carbohydrates was increased to 58 mg/L. Cu²⁺, Mg²⁺, Zn²⁺ in the EPS were increased in the range of 1.6–3.3 mg/L. The high concentration of EPS that is produced has a higher chelation potential in the formation of ligand complexes with metals or cations than that in a conventional continuous stirred tank reactor (CSTR). The EPS directly affected the decrease in the permeate flux, which resulted in the clogging of the membrane.     

Syntheses and Characterization of Novel Perovskite-Type LaScO3-Based Lithium Ionic Conductors

Perovskite-type lithium ionic conductors were explored in the (Li_xLa_1−x/3)ScO₃ system following their syntheses via a high-pressure solid-state reaction. Phase identification indicated that a solid solution with a perovskite-type structure was formed in the range 0 ≤ x < 0.6. When x = 0.45, (Li_0.45La_0.85)ScO₃ exhibited the highest ionic conductivity and a low activation energy. Increasing the loading of lithium as an ionic diffusion carrier expanded the unit cell volume and contributed to the higher ionic conductivity and lower activation energy. Cations with higher oxidation numbers were introduced into the A/B sites to improve the ionic conductivity. Ce⁴⁺ and Zr⁴⁺ or Nb⁵⁺ dopants partially substituted the A-site (La/Li) and B-site Sc, respectively. Although B-site doping produced a lower ionic conductivity, A-site Ce⁴⁺ doping improved the conductive properties. A perovskite-type single phase was obtained for (Li_0.45La_0.78Ce_0.05)ScO₃ upon Ce⁴⁺ doping, providing a higher ionic conductivity than (Li_0.45La_0.85)ScO₃. Compositional analysis and crystal-structure refinement of (Li_0.45La_0.85)ScO₃ and (Li_0.45La_0.78Ce_0.05)ScO₃ revealed increased lithium contents and expansion of the unit cell upon Ce⁴⁺ co-doping. The highest ionic conductivity of 1.1 × 10⁻³ S cm⁻¹ at 623 K was confirmed for (Li_0.4Ce_0.15La_0.67)ScO₃, which is more than one order of magnitude higher than that of the (Li_xLa_1−x/3)ScO₃ system.     

Direct quantum chemical calculation of rotatory strengths of methylpyrrolidones : Model compounds containing a peptide group

CNDO/S method is used to compute the rotatory strengths of L-5-methylpyrrolid-2-one and S-3-methylpyrrolid-2-one, cyclic compounds containing a peptide group. The observed circular dichroism (CD) bands in the regions of 185 and 220 nm corresponded to π → π^* and n → π^* transitions, respectively. The computed rotatory strengths indicate that nonplanarity of pyrrolidone ring makes a substantial contribution to the CD of compounds under consideration. The comparison of computed and experimental rotatory strengths suggests that both compounds have a nonplanar ring conformation.     

On the influence of ionic strength on the equilibrium constant of an ion-molecule reaction

Concentration formation constants for the 18-crown-6-sodium ion complex in anhydrous methanol solutions were measured as a function of the ionic strength of the solution. The K_c values remained reasonably constant for I_c ? 0.05 mol dm^?3 At higher ionic strengths the K_c values begin to decrease. The infinite-dilution formation constant was 2.2 × 10⁴.     

Influence de la temperature et du gradient de vitesse sur la viscosite des solutions diluees de xanthane

The dependence of the relative viscosity of a dilute xanthan solution (0.4 g·l^?1) has been studied as a function of temperature (20–70°) and of the ionic strength of the solvent. When the rate of shear exceeds 100 sec^?1, the viscosity can be expressed as γ&#x030A; the exponent (n ? 1) varies with the polymer conformation. In aqueous solution in the absence or in the presence of added salt at a temperature above the melting temperature T_M (depending on the ionic strength of the solvent), the exponent (n ? 1) is ?0.285 and corresponds to the unordered conformation; at temperatures below T_M, the local helical conformation is rigid and (n ? 1) is ～ ?0.44 almost independent of the temperature.     

Calcium—malonate complexes in aqueous solution. Thermodynamic parameters and their ionic strength dependence

Formation constants of calcium complexes with malonate (mal^2?), in the ranges 10 ? t ? 50°C and 0.05 ? I ? 0.9 mol dm^?3, were determined by means of alkalimetric titrations in aqueous solution. The species found in this system were [Ca(mal)]⁰ and [Ca(Hmal)]⁺; also, the hydrolysis of Ca²⁺ was taken into account. The effect of ionic medium on the formation constants was studied by using different background salts (KNO₃, NaNO₃, Et₄NI and Et₄NBr); the parameters defining ionic strength dependence were calculated from the values of stability constants obtained at different ionic strengths. ΔH and ΔS values were obtained from temperature coefficients of stability constants.A general equation, useful for correlating the formation constants in the studied temperature and ionic strength ranges, has been found. It has also been found that, by considering all the significant interactions in the solution, the formation constants are dependent on temperature and ionic strength only.Literature data are discussed and compared with those obtained in this work.     

Thermodynamic study of the complexation processes between 6,7-dihydro-3(H)-6-methyl-5-methoxy-7-oxo-vic-triazolo (4,5-d) pyrimidine and Cu(II), Zn(II), Cd(II) and Hg(II)

The compound 6,7-dihydro-3(H)-6-methyl-5-methoxy-7-oxo-vic-triazolo (4,5-d) pyrimidine (LH) has been characterized by IR, ¹H-NMR and UV-visible spectroscopy. Furthermore, its acid behaviour in aqueous solutions at variable temperatures and ionic strengths have been studied.The stability constants of the complexes formed by LH with Cu(II), Zn(II), Cd(II) and Hg(II) metal ions at different ionic strengths and temperatures have been calculated by the method of Chabereck and Martell. From these data, the thermodynamic functions for the corresponding complexation processes have been obtained.     

Silica gel modified with 1-(2-aminoethyl)-3-phenylurea for selective solid-phase extraction and preconcentration of Sc(III) from environmental samples

A new method that utilizes 1-(2-aminoethyl)-3-phenylurea-modified silica gel as a solid-phase extractant has been developed for preconcentration of trace Sc(III) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace level of Sc(III) were optimized using batch and column procedures in detail. The optimum pH value for the separation of Sc(III) on the new sorbent was 4 and complete elution of Sc(III) from the sorbent surface was carried out using 1.0 mL of 0.1 mol L⁻¹ HCl. Common coexisting ions did not interfere with the separation and determination of the analyte. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 32.5 mg g⁻¹ while the time of 95% adsorption was less than 2 min. The detection limit of present method was found to be 0.091 μg g⁻¹, and the relative standard deviation (RSD) was lower than 3.0% (n = 8). The method was successfully applied for the preconcentration of trace Sc(III) in the environmental samples with satisfactory results.     

GPC,CD and sedimentation analysis of poly-Lys and branched chain poly-Lys-poly-DL-Ala polypeptides

Three different poly-L-lysine (pLys) samples and a branched polypeptide poly-[L-Lys-(DL-Ala)_m] (poly-L-Lys-poly-DL-Ala, AK) were synthetized. Relative molar mass distribution, its average and the degree of polymerisation were determined by sedimentation analysis and gel permeation chromatography (GPC). The conformation of the polymers in solution was studied by circular dichroism (CD) spectroscopy at various pH values and ionic strengths. The data obtained by different methods were compared.A preliminary account of this work was read at the 4^th Conference on Colloid Chemistry, Eger, 1983.