Presence Of PEG6000 Research Articles

Tuning polymorphs of precipitated calcium carbonate from discarded eggshells: effects of polyelectrolyte and salt concentration.

Biowaste eggshells are a valuable source of calcium carbonate suitable for various applications. In this study, spherical vaterite and calcite calcium carbonate polymorphs have been synthesised from discarded eggshells by the precipitation technique at ambient temperature. The influence of initial salt concentration with different polyelectrolytes such as ethylene glycol (EG), polyethylene glycol (PEG, 600 and 6000), and poly(sodium 4-styrenesulfonate) (PSS) at various w/v% concentrations on the polymorph crystal formation of precipitated calcium carbonate (PCC) particles was studied. The results indicated that PCC crystals with spherical, star-shaped and yarn shaped morphologies can be obtained based on the concentration of calcium ions and the presence of different polyelectrolyte solution. At low salt molar concentration, PEG-6000 and PSS polyelectrolytes were found to promote the formation of spherical vaterite calcium carbonate particles with particle mean diameters of 5.05 μm and 2.17 μm, respectively. Furthermore, silver nanoparticles were also loaded into the PCC particles in situ, and the surface area significantly increased from 2.2813 m2 g−1 in untreated ground eggshells to 30.4632 m2 g−1 in PCC particles in the presence of PSS and silver colloid solution. The EDS mapping revealed the average wt% of silver atoms loaded in PCC particles in the presence of PSS polyelectrolyte was lower (1.44 wt%) than in the presence of PEG-6000 (4.27 wt%) due to the silver encapsulation possibility during the core–shell formation, as confirmed by SEM images. The silver nanoparticle-loaded PCC particles in this study can be incorporated into the polymer matrix and employed for antimicrobial food packaging or wound dressing application.

Prokaryotic Expression of Phosphoenolpyruvate Carboxylase Fragments from Peanut and Analysis of Osmotic Stress Tolerance of Recombinant Strains.

Phosphoenolpyruvate carboxylase (PEPC) is a ubiquitous cytosolic enzyme that catalyzes the irreversible β-carboxylation of phosphoenolpyruvate (PEP) in presence of HCO3− to produce oxaloacetate (OAA) during carbon fixation and photosynthesis. It is well accepted that PEPC genes are expressed in plants upon stress. PEPC also supports the biosynthesis of biocompatible osmolytes in many plant species under osmotic stress. There are five isoforms of PEPC found in peanut (Arachis hypogaea L.), namely, AhPEPC1, AhPEPC2, AhPEPC3, AhPEPC4, and AhPEPC5. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the gene expression patterns of these AhPEPC genes were different in mature seeds, stems, roots, flowers, and leaves. The expression of all the plant type PEPC (PTPCs) (AhPEPC1, AhPEPC2, AhPEPC3, and AhPEPC4) was relatively high in roots, while the bacterial type PEPC (BTPC) (AhPEPC5) showed a remarkable expression level in flowers. Principal component analysis (PCA) result showed that AhPEPC3 and AhPEPC4 are correlated with each other, indicating comparatively associations with roots, and AhPEPC5 have a very close relationship with flowers. In order to investigate the function of these AhPEPCs, the fragments of these five AhPEPC cDNA were cloned and expressed in Escherichia coli (E. coli). The recombinant proteins contained a conserved domain with a histidine site, which is important for enzyme catalysis. Results showed that protein fragments of AhPEPC1, AhPEPC2, and AhPEPC5 had remarkable expression levels in E. coli. These three recombinant strains were more sensitive at pH 9.0, and recombinant strains carrying AhPEPC2 and AhPEPC5 fragments exhibited more growth than the control strain with the presence of PEG6000. Our findings showed that the expression of the AhPEPC fragments may enhance the resistance of transformed E. coli to osmotic stress.

Effect of Osmotic Conditioning in Physiological Quality of Cucumis sativus L. and Solanum lycopersicum L. Seeds

The human consumption of vegetables in different parts of the world is quite high, among them tomato stands out on a larger scale and not so far, also is cucumber, both with great economic importance. Due to the problems regarding the vigor of many seeds, techniques that seek to improve the establishment of the seedlings in a uniform way have been implemented. One technique is the osmotic conditioning to which the seeds are submitted, for which compound solutions such as polyethylene glycol or potassium nitrate can be used, with which very satisfactory results are obtained under laboratory and field conditions The objective of this investigation was to evaluate the effect of different doses and osmotic solutions on the physiological quality of seeds of tomato (Solanum lycopersicum L.) and cucumber (Cucumis sativus L.) in laboratory and field conditions. The evaluated variables were germination percentage, germination speed index, root length and emergence of seedlings. The tomato seeds were conditioned with PEG-6000 (-0.2, -0.4, -0.6 and -0.8 Mpa) and stored for a 30 days period, and as for the cucumber seeds with PEG-6000 (-0.2 and -0.1 Mpa) and with KNO³ (100 mg and 300 mg) with a storage period of 45 days. It is concluded that, in tomato seeds, germination did not present statistical differences, however, the variables referring to vigor were favored with the conditioning in the presence of PEG-6000 with the (-0.2 Mpa) concentration, while in cucumber seeds the germination percentage was better using PEG 6000 compared to nitrate, while for vigor variables it behaved better in the presence of a concentration of (-0.2 Mpa) of PEG.

Construction of recombinant fusant yeasts for the production of cider with low alcohol and enhanced aroma

Increasing levels of alcohol abuse and changes in consumer interests have motivated the production of ciders with enhanced aroma and flavor, but low alcohol content. The improvement of fermentation has always been an important issue in the brewing industry. In this study, new recombinant fusant yeasts based on Saccharomyces cerevisiae and Candida ethanolica were constructed by protoplast fusant. The combination of ultrasonic and enzymatic hydrolysis could significantly improve protoplast formation and regeneration rates. In the presence of PEG-6000, the 24 fastest-growing regenerated colonies were selected for further fermentation and re-screening identification, and nine stable fusant strains were inoculated in the subsequent fermentation. The alcohol content of the ciders was 2.0–5.2%, which was much lower than that of the parental strain. Fusants R6 and R7 revealed the best fermentation performance. The sensory scores of fusants R5 and R6 exhibited excellent performance than others. GC–MS analysis and fuzzy comprehensive evaluation showed fusant R6 displayed superior performance and desirable properties from both parental strains. This study demonstrated that recombinant fusant yeast of R6 has great potential for the production of high-quality, low-alcohol cider. The present work provides new avenues for the construction of potent recombinant fusant yeasts and a new strategy for the production of low-alcohol cider with enhanced aroma.

Dual substrate/solvent- roles of water and mixed reaction-diffusion control of β-Galactosidase catalyzed reactions in PEG-induced macromolecular crowding conditions

Here we studied the effect of molecular crowding on the hydrolysis of ortho- and para-nitrophenyl-β-D-galactopyranosides (ONPG, PNPG) catalysed by Escherichia coli β-Galactosidase in the presence of 0–35%w/v 6kD polyethyleneglycol (PEG6000). The Eadie-Hofstee data analysis exhibited single straight lines for PNPG at all [PEG6000] as well as for ONPG in the absence of PEG6000 so a Michaelian model was applied to calculate the kinetic parameters KM and kcat (catalytic rate constant) values. However, for ONPG hydrolysis in the presence of PEG6000, the two slopes visualized in Eadie-Hofstee plots leaded to apply a biphasic kinetic model to fit initial rate vs. [ONPG] plots hence calculating two apparent KM and two kcat values. Since the rate limiting-step of the enzymatic hydrolysis mechanism of ONPG, but not of PNPG, is the water-dependent one, the existence of several molecular water populations differing in their energy and/or their availability as reactants may explain the biphasic kinetics in the presence of PEG6000. With PNPG, KM as well as kcat varied with [PEG6000] like a parabola opening upward with a minimum at 15 %w/v [PEG6000]. In the case of ONPG, one of the components became constant while the other component exhibited a slight increasing tendency in kcat plus high and [PEG6000]-dependent increasing KM values. Sedimentation velocity analysis demonstrated that PEG6000 impaired the diffusion of β-Gal but not that of substrates. In conjunction, kinetic data reflected complex combinations of PEG6000-induced effects on enzyme structure, water structure, thermodynamic activities of all the chemical species participating in the reaction and protein diffusion.

A novel osmotic pressure strategy to improve erythritol production by Yarrowia lipolytica from glycerol.

Polyethylene glycol (PEG) is polymer that was used to replace NaCl (reference media) as an osmotic stress agent for the synthesis of erythritol by the osmophilic yeast Yarrowia lipolytica. Two strains, the wild-type strain IMUFRJ 50682 and the lab strain W29, were grown in the presence of PEG of different molecular weights. For strain IMUFRJ 50682, the erythritol titer was increased by 40% in the presence of PEG2000 as compared to the reference media (with NaCl). A similar increase was also observed for strain W29, except that it occurred in the presence of PEG6000. Moreover, in those experimental conditions neither strain produced mannitol, in contrast to the control medium. These results highlight that PEG could be used to increase erythritol productivity and to simultaneously inhibit mannitol synthesis, representing a good substitute for NaCl as an osmotic stress agent.

Regulation of IAA Biosynthesis in Azospirillum brasilense Under Environmental Stress Conditions.

Indole-3-acetic acid (IAA) is one of the most important molecules produced by Azospirillum sp., given that it affects plant growth and development. Azospirillum brasilense strains Sp245 and Az39 (pFAJ64) were pre-incubated in MMAB medium plus 100mg/mL L-tryptophan and treated with or exposed to the following (a) abiotic and (b) biotic stress effectors: (a) 100mM NaCl or Na2SO4, 4.0% (w/v) PEG6000, 0.5mM H2O2, 0.1mM abscisic acid, 0.1mM 1-aminocyclopropane 1-carboxylic acid, 45°C or daylight, and (b) 4.0% (v/v) filtered supernatant of Pseudomonas savastanoi (Ps) or Fusarium oxysporum (Fo), 0.1mM salicylic acid (SA), 0.1mM methyl jasmonic acid (MeJA), and 0.01% (w/v) chitosan (CH). After 30 and 120min of incubation, biomass production, cell viability, IAA concentration (µg/mL), and ipdC gene expression were measured. Our results show that IAA production increases with daylight or in the presence of PEG6000, ABA, SA, CH, and Fo. On the contrary, exposure to 45°C or treatment with H2O2, NaCl, Na2SO4, ACC, MeJA, and Ps decrease IAA biosynthesis. In this report, growth and IAA biosynthesis in A. brasilense under biotic and abiotic stress conditions are discussed from the point of view of their role in bacterial lifestyle and their potential application as bioproducts.

Effet de plusieurs méthodes de scarification et du stress osmotique sur la germination des graines de Robinia pseudoacacia L.

The planting of several species adapted to forests areas in the Saharan Atlas would allow one to better fight against the desertification of the vegetation cover of these fragile areas. Thanks to its rapid growth on degraded soils, Robinia pseudoacacia L. has an advantage in the repopulation of these areas undergoing desertification. Operation of this large-scale tree requires good control of germination conditions and growth of plants. The scarification of the seeds of Robinia pseudoacacia L. is necessary to allow the absorption of water by the seeds. Our results show that mechanical scarification with sulphuric acid (75minutes), boiling water (90minutes) and scarification by microwaves (700W) (105seconds) give the best germination rates. The presence of PEG6000 in the imbibition's solutions reduces considerably the germination rate of the seeds of R. pseudoacacia L. A 70 % decrease in the optimal rate of germination is observed when the osmotic pressure of the imbibition solution is at –4.65 bar.

Determination of the phase diagram for the crystallization of L‐asparaginase II by a turbidity technique ‐ part II. ‐MPD and crystallography studies‐

The phase diagram for the crystallization of L‐asparaginase II including the metastable zone width (MZW), in the presence of PEG6000 and ethanol, respectively, has been studied by an online turbidity technique out of the crystallization in solution (see part I of this work ). Here this paper describes a further investigation on constructing a phase diagram including MZW for the crystallization of L‐asparaginase II with a different precipitant agent of 2‐methyl‐2, 4‐pentandiol (MPD). Along with the phase diagram, the single crystal X‐ray data were successfully collected at 100K from a crystal formed in the presence of 26% (v/v) MPD. The crystals indicate an orthorhombic form and belong to the space group of P212121 with the unit cell parameters a = 93.9, b = 125.77, c = 151.75Å. The crystal diffracted up to a resolution of 2.88 Å.

Synthesis and characterization of low-dimensional ZnO nanocrystals in an aqueous solution

Low-dimensional ZnO nanocrystals were successfully synthesized at low temperature in an aqueous solution. XRD, TEM, SEM, TG–DTG and IR have been employed to characterize the as-prepared samples. Rodlike ZnO powders with aspect ratio of about 10–16 were easily obtained in the presence of PEG-6000 at low synthesis temperature (50°C, 70°C), and the length and diameter were 200–250nm and 15–20nm, respectively. The shape changed to prismatic-like when the reaction temperature raised to 80°C and tended to be spherical at 95°C. The results show that the temperature plays an important role in the formation and oriented growth of ZnO nanocrystals. Additionally, using doped-ZnO powders via this direct precipitation method after sintering in air at 1150°C for 2h, the varistor can be produced having a sintered density 94.5% of its theoretical density with grain size of ∼4.5μm and a nonlinear coefficient of ∼23.

Thermodynamic studies of the ionic liquid 1-hexyl-3-methylimidazolium chloride [C 6mim][Cl] in polyethylene glycol aqueous solutions

Vapour pressure osmometery (VPO) measurements at T = 308.15 K for {[C 6mim][Cl] + water}, {[C 6mim][Cl] + (0.005, 0.0155, and 0.0263) mol · kg −1 PEG2000 + water} and {[C 6mim][Cl] + (0.0017, 0.0052, and 0.0088) mol · kg −1 PEG6000 + water} systems and isopiestic measurements at T = 298.15 K for {[C 6mim][Cl] + PEG2000 + water} and {[C 6mim][Cl] + PEG6000 + water} systems have been carried out. The VPO measurements were carried out at very low concentrations of PEG and from which the values of the water activities, osmotic coefficients, vapour pressure and activity coefficients were obtained. The data obtained from the VPO method show that over the whole concentration range of the ionic liquid (IL), the activity coefficients of [C 6mim][Cl] in the presence of PEG2000 are increased. Although, at high IL concentrations, the values of the activity coefficient of [C 6mim][Cl] in the presence of PEG6000 are also increased, however for low concentrations of IL the values of the activity coefficient of [C 6mim][Cl] in pure water are larger than those in aqueous PEG6000 solutions. For a known IL concentration, the values of water activity coefficient for the binary {[C 6mim][Cl] + water} system are larger than those for the ternary {[C 6mim][Cl] + PEG + water} systems and decrease by increasing the concentration of PEG or decreasing the molar mass of PEG. The constant water activity lines of the all ternary systems obtained from the isopiestic method show positive deviation from the linear isopiestic relation (Zdanovskii–Stokes–Robinson rule) derived using the semi-ideal hydration model. The results have been interpreted in terms of the solute–water and solute–solute interactions.

Enhanced saccharification of SO2 catalyzed steam-exploded corn stover by polyethylene glycol addition

Abstract Corn stover is a renewable, low cost and abundant feedstock in China. Its effective utilization is crucial for providing bioenergy, releasing environmental pollution and increasing farmers’ income. This aim of this study was to obtain the efficient saccharification of SO2 catalyzed steam-exploded corn stover (SSECS) by polyethylene glycol (PEG) addition. According to the results, adding PEG6000 could lower the enzyme loading by 33.3%. With 20% solid loading, the highest glucose concentration of 102 g L−1 and 91.3% saccharification yield were obtained using 30 CBU (g glucan)−1 β-glucosidase and 10 FPU (g glucan)−1 cellulase in presence of PEG6000. In addition, protein and enzyme activities assays in the supernatants revealed that PEG could facilitate the desorption of enzyme protein from lignocellulose. These indicated that PEG addition not only can enhance enzymatic saccharification at high substrate concentration, but also can improve enzyme recycling by reducing the enzyme activity loss caused by adsorption during the hydrolysis.

Encapsulation of diclofenac sodium with acidic copolymer hydrogels based on PEG/poly(N‐isopropylacrylamide‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) semi‐interpenetrating network using in situ loading technique

AbstractA pH‐ and temperature‐responsive semi‐interpenetrating copolymer PEG6000/poly(NIPA‐co‐AMPS) (PEG/AMPS‐co‐NIPA SIPN), for short PEG SIPN, was made by ammonium persulfate‐initiated suspension copolymerization of N‐isopropylacrylamide, 2‐acrylamido‐2‐methylpropanesulphonic acid, and N,N′‐methylene‐bis‐acrylamide (MBAA; crosslinker) in the presence of PEG6000. The PEG SIPN copolymer matrices containing nanostructures made in the high‐temperature copolymerization resulted in channels for PEG and facile migration of drugs. In drug encapsulation or drug‐loading process, one can easily ignore or pay less attention to the interaction between a drug and its encapsulation materials; however, the ignored interactions may induce problems in drug properties or the release behavior in use. Sodium diclofenac (DFNa) precipitates as the carboxylic acid form in an acidic environment, and it is challenging to encapsulate sodium diclofenac in such an acidic matrix without precipitation of the sparingly soluble acid form of DFNa on the surface of the polymer substrate. To avoid bulky precipitation in drug loading, an in situ loading technique was developed for producing gel spheres with DFNa uniformly distributed in the polymer matrix. The technique is based on fast polymerization of spherical droplets of a pregel solution in which the drug is dissolved. Diffusion‐loading prodrugs were made in comparison with in situ loading prodrugs in thermal, release kinetics, and release behavior. Drug release profiles (in pH 7.4 phosphate buffer) show that the new drug loading technique gives controlled release during a period of about 7 days at 37°C. By contrast, gel spheres loaded with sodium diclofenac using the conventional diffusion technique produced almost total release of the drug within about 24 h. The thermal stability of sodium diclofenac, the PEG/AMPS‐co‐NIPA SIPN, and the prodrugs made with the SIPN and sodium diclofenac was studied. A near zero‐order release kinetics was found in the in vitro release of sodium diclofenac with in situ loading PEG SIPN prodrug. We have, for the first time, studied sodium diclofenac release behavior from the PEG SIPN hydrogel systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Coleoptile cuticle of barley is necessary for the increase in appressorial turgor pressure of Blumeria graminis for penetration

To determine whether the cuticle of the barley coleoptile is responsible for a rise in appressorial turgor pressure in Blumeria graminis, we determined the appressorial turgor pressure by measuring cytorrhysis and plasmolysis in the presence of PEG6000. Appressorial turgor pressure significantly increased 13–14 h after inoculation. On the other hand, when the cuticle was completely removed from the barley coleoptile surface with diethyl ether, turgor pressure did not increase. Moreover, when we then recoated the surface with the exogenous barley cuticle fraction, appressorial turgor pressure significantly increased 12–13 h after inoculation. These results suggest that the cuticle on the surface of the barley coleoptile is necessary for the increase in the appressorial turgor pressure.

Hydrogen evolution and permeation into steel during zinc electroplating; effect of organic additives

The Devanathan and Stachurski diffusion membrane method was used to study the evolution of hydrogen and its permeation into a steel sheet during cathodic charging from a chloride electrolyte or during zinc electroplating. The influence of four different organic compounds, which are the components of various formulations derived to improve zinc electrocoatings, were also tested. At a high-charging current density, the permeation transients obtained in a chloride electrolyte without zinc ions exhibit a maximum attributed to hydrogen trapping in the subsurface layer on the entry side. The concentration of adsorbed hydrogen on the steel surface depends not only on the cathodic current density and the composition of the solution, but also on the influence of the organic additives on the recombination of hydrogen atoms. During zinc electrodeposition, the coating covers the substrate in a few seconds and acts as a barrier for hydrogen absorption. The permeation rate depends on the cathodic current density but also on the concentration of ZnCl2 in correlation with the porosity of the coating. It is shown that steel substrate hydrogenation (beneath the zinc coating) is strongly reduced in the presence of a combined additive, composed of four compounds in appropriate amounts as well as in the presence of PEG6000 in the plating bath. This effect, which is correlated to the modification of the hydrogen evolution process, can be used to hinder the severe drawbacks caused by hydrogen penetration into the steel substrate.

Isolation of L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase from Chromatium vinosum.

The enzyme ribulose bisphosphate carboxylase/oxygenase has been purified from Chromatium vinosum. When an extract is subjected to centrifugation at 35,000 X g in the presence of polyethylene glycol (PEG)-6000 and the supernatant is treated with 50 mM Mg2+ and the precipitate is then fractionated by vertical centrifugation into a reoriented sucrose gradient followed by chromatography on diethylaminoethyl (DEAE)-Sephadex A50, the resultant enzyme contains large (L) and small (S) subunits. Alternatively, centrifugation of extracts at 175,000 X g in the presence of PEG-6000 followed by fractionation with Mg2+, density gradient centrifugation, and chromatography on DEAE-Sephadex A50 yields an enzyme free of small subunits. The two forms have comparable carboxylase and oxygenase activities and have compositions and molecular weights corresponding to L8 and L8S8 enzymes. The amino acid compositions of L and S subunits are reported. The L8S8 enzyme from spinach cannot be similarly dissociated by centrifugation at 175,000 X g in the presence of PEG-6000.