Aqueous Sugar Solutions Research Articles

Effect of methane–sugar interaction on the solubility of methane in an aqueous solution

In this study, the effect of methane–sugar interaction on the solubility of methane in an aqueous solution at ambient pressure was investigated. Various sugars, such as fructose, glucose, sucrose, maltose, and raffinose, were used, and depending on the type and concentration of sugar, the methane solubility increased from 21.72mg/L (in pure water) to 24.86mg/L. Sugars with a low hydrogen-bonding number between the water and sugar molecules exhibited a large enhancement in methane solubility. The solute partitioning model and molecular dynamics simulations were employed to verify the results obtained for the experimental solubility of methane in aqueous sugar solutions.

A research on the chemical and microbiological qualities of honeys sold in Istanbul

Abstract Honey, produced by honeybees from nectar in flowers and plants, is an aqueous supersaturated sugar solution, mainly composed of fructose and glucose. The quality and biochemical properties of honey are related to honey maturity, production methods, processing and storage conditions, climatic conditions as well as the nectar source of the honey. In this study, 35 honey samples of different sizes and packaging all of which were sold in Istanbul were examined in terms of some physicochemical and microbiological properties. All samples were floral liquid honey. The physicochemical characterizations were as follows: average moisture (16.31±1.40%), ash (0.30±0.29%), hydroxymethylfurfural (HMF) (8.09±7.63 mg/kg), pH (4.32±0.34), acidity (30±9 meq/kg). In addition, total mesophilic aerobic bacteria, Enterobacteriaceae, yeast and mold analyses were performed in these samples. According to the microbiological analyses; the average total number of mesophilic aerobic bacteria was 2.68 log cfu/g. Enterobacteriaceae have not been observed in the samples. However, in three samples, mold-yeasts were detected at the levels between 1.30 and 1.60 log cfu/g.

Static and Dynamic Study of Disaccharides Trehalose, Maltose and Sucrose

In this work, electronic structure calculations and Molecular Dynamics (MD) simulations were performed in order to carry out a static and dynamic study of disaccharides, trehalose, sucrose and maltose. These three disaccharides share the same chemical formula and the same number of OH groups; however, it has been widely shown that trehalose has a superior ability to protect biological structures. In order to contribute to the understanding of the factors that determine this ability of trehalose, in this work a comparative study of the three disaccharides in gas phase and dilute aqueous solution is performed. A detailed analysis of hydrogen bonds (HBs) was carried out using Quantum Theory of Atoms In Molecules (QTAIM) on wave functions obtained at B3LYP/6-311++G** level. Besides, stereoelectronic effects were examined by Natural Bond Orbital (NBO) analysis. In addition, the intra- and intermolecular HB interactions in MD runs of infinitely dilute aqueous solution of sugars have been monitored. Results show that the three disaccharides form a significant number of HBs of C-H∙∙∙O type, mainly in trehalose. An intermolecular bond of this type determines the conformational rigidity of trehalose in solution which contributes to stabilize a clam shell conformation as the one observed in the crystal. In this disaccharide, hydrogen bonds are more labile, showing a quickly exchange of the water molecules that form these HBs. This fact slows down ice formation and could be the explanation for trehalose capabilities as a cryoprotectant.

Binding of boronic acids with sugars in aqueous solution at physiological pH - Estimation of association and dissociation constants using spectroscopic method

Sugar sensing and continuous monitoring of glucose (CGM) play an important and vital role in controlling diabetes. Even though present enzyme-based sugar sensors are doing well, research is going on globally for the design of new sensors to address some of their limitations. Among many, sensors based on fluorescent intensity change are drawing more attention; especially those which are based on boronic acid derivatives are more popular because of their ability to reversibly bind diol-containing compounds. Here we have investigated the binding ability of two boronic acid derivatives namely, 5-chloro-2-methoxyphenylboronic acid [5CMPBA] and 2-methoxypyridin-3-yl-3-boronic acid [2MPBA] with mono and disaccharides (sugars) in aqueous medium at physiological pH7.4. The sugar concentration is kept nearly 1000 times more than that of boronic acid. Binding constants (Ka) and dissociation constants (KD) are calculated using Benesi-Hildebrand equation and Lineweaver-Burk equation. The effect of intramolecular hydrogen bonding on fluorescence intensity is observed. The higher value of Ka in case of monosugars indicates the role of structural change in sugar that arises due to mutarotation in binding interactions.

Selective diffusion of glucose, maltose, and raffinose through calcium alginate membranes characterized by a mass fraction of guluronate

Glucose was selectively separated from an aqueous solution of mixed sugars (glucose 180Da, maltose 342Da, and raffinose 504Da) by static diffusion, and not ultrafiltration, without the driving force of pressure. The calcium alginate membrane described in this study provides a simple technical medium for sugar separation. Excellent selectivity based on the molecular size of sugar was realized. The mass fraction of homopolymeric blocks of guluronate in alginate polymer chains (FGG) was defined as a gravimetric ratio of homopolymeric blocks of α-l-guluronate in sodium alginate to the total mass of the sodium alginate polymer. FGG was a key factor for regulating the mass transfer characteristics of the calcium alginate membrane. Two different FGG membranes were employed to assess the selective separation of glucose. The effective diffusion coefficient in the membrane (Deff) was determined from the mass transfer flux through the calcium alginate membrane. The effective diffusion coefficient in the FGG 0.56 membrane exhibited a 38-fold decrease in the mixed system of the three sugars, even when the molecular weight showed only a 2.8-fold increase from glucose to raffinose. In the FGG 0.18 membrane, the effective diffusion coefficient exhibited a 14-fold decrease. The mass fraction of guluronate blocks was a dominant factor that regulated the selective diffusion of the sugars. The design of a calcium alginate membrane based on the mass fraction of guluronate blocks is promising for desirable selective sugar separation in industrial applications.

Competitive Adsorption of Substrate and Solvent in Sn-Beta Zeolite During Sugar Isomerization.

The isomerization of 1,3‐dihydroxyactone and d‐glucose over Sn‐Beta zeolite was investigated by in situ 13C NMR spectroscopy. The conversion rate at room temperature is higher when the zeolite is dehydrated before exposure to the aqueous sugar solution. Mass transfer limitations in the zeolite micropores were excluded by comparing Sn‐Beta samples with different crystal sizes. Periodic density functional theory (DFT) calculations show that sugar and water molecules compete for adsorption on the active framework Sn centers. Careful solvent selection may thus increase the rate of sugar isomerization. Consistent with this prediction, batch catalytic experiments show that the use of a co‐solvent, such as tetrahydrofuran, that strongly interacts with the Sn centers suppresses glucose isomerization. On the other hand, the use of ethanol as cosolvent results in significantly higher isomerization activity in comparison with pure water because of decreased competition with glucose adsorption on zeolitic Sn sites.

MOF sorbent boosts bioethanol production

A porous metal-organic framework sorbent could boost the efficiency of ethanol production from cellulosic biomass by trapping compounds that inhibit fermentation, according to a study (Chem. Commun. 2016, DOI: 10.1039/c6cc05864g). Woody plants and grasses hold enormous supplies of cellulose, from which ethanol can be produced via fermentation of sugars extracted from the plant materials. This route to ethanol production currently generates hundreds of millions of liters of the renewable fuel annually, a value that is expected to climb. Extracting the sugars from biomass requires breaking down the plant material, which is notoriously recalcitrant. Biofuel manufacturers typically rely on harsh acid treatments to do that job. The process works well, but it generates aqueous sugar solutions contaminated with 5-hydroxymethylfurfural (HMF) and other furanics. Those compounds are toxic to the organisms that do the fermentation and thereby limit the process efficiency. They are also tough to separate from sugar s...

Glass Transition and Dynamics of the Polymer and Water in the Poly(vinylpyrrolidone)-Water Mixtures Studied by Dielectric Relaxation Spectroscopy.

In this study, broadband dielectric spectroscopy and differential scanning calorimetry (DSC) measurements are performed to study the dynamics of water and polymers in an aqueous solution of poly(vinylpyrrolidone) (PVP) with concentrations of 60, 65, and 70 wt % PVP in a temperature range of 123-298 K. Two distinct relaxation processes, l- and h-processes, which originate from the segmental chain motion of PVP and the primary relaxation process of water, respectively, are observed simultaneously. The relationship between l- and h-processes and their temperature dependences mimic those of the α-process and Johari-Goldstein β-process, which are observed in ordinal glass formers. The relaxation time of the l-process, τl, obeys the Vogel-Fulcher (VF)-type temperature dependence, and the glass-transition temperature of the l-process, Tg,l, which is defined by the temperature that is reached in a τl of 100-1000 s, shows good agreement with the calorimetric Tg obtained by DSC. The temperature dependence of the relaxation time of the h-process, τh, exhibits a crossover from VF to Arrhenius behavior at the so-called fragile-to-strong transition (FST) of water at Tg,l. The temperature dependence of the relaxation strength of the h-process, Δεh, increases with a decrease in temperature from 298 K to Tg,l. Below Tg,l, Δεh is nearly constant or slightly decreases with decreasing temperature. According to previous studies on aqueous solutions of sugars and alcohols, the Δε of the ν-process, which originates from local motion of water, decreases with decreasing temperature above the Tg of the α-process, which originates from the cooperative motion of the solute and water. Therefore, the l-process in the PVP-water mixture is not a result of the cooperative motion of PVP and water but rather a result of the polymer-polymer cooperative motion of PVP. In addition, agreement among Tg,l, the temperature of the FST of water, and calorimetric Tg suggests that the FST of water occurs at Tg.

The Effect of Differences in the Diffusion Coefficients of Components on the Onset of Convection in Isothermal Multicomponent Systems

Two series of experiments on the formation of convective flows in multicomponent liquid and gaseous mixtures are considered. In the first series, the convective structures arising during the diffusion of a binary aqueous solution of salt and sugar in an aqueous solution of pure salt were studied using the schlieren method. The observed behavior of convective cells corresponds to the instability similar to the "finger structures". In the second series, the experiments were conducted to determine the effective diffusion coefficients as a function of pressure in gas mixtures 0.5504 CH4 + 0.4496 Ar – N2 and 0.5994 H2 + 0.4006 Ar – N2. Our experiments have shown that the onset of convective flows both in liquid and gaseous multicomponent mixtures is due to the difference in the interdiffusion coefficients of the components. The experimental data for the ternary gas mixtures are described in the framework of the linear theory of stability.

Carbohydrate-surfactant interactions in aqueous and mixed organic solvents at various temperatures: Volumetric, compressibility and acoustical studies

Herein, we report the detailed volumetric, compressibility and acoustical studies of carbohydrate-surfactant interactions in aqueous and mixed organic solvents at various temperatures. The interactions between sugars (ribose, glucose, sucrose and raffinose) and sodium dodecyl sulfate (SDS, an anionic surfactant) were studied in aqueous solutions at various temperatures, i.e. 293.15, 303.15 and 313.15K using density and speed of sound measurements. Further, to clearly understand the sugar–surfactant interactions, various parameters such as molar volume (Vϕ), isentropic compressibility (κs) and apparent molar isentropic compressibility (κϕ,S) were calculated from the obtained data. The observed results revealed that different saccharides exhibit pronounced effect on micellization of SDS which might be due to the differences in number of –OH linkages. The increase in such linkages results in dominance of sugar–water interactions, thus favoring the micelle formation. Further, to support such conclusion, viscosity measurements (relative viscosity and viscous relaxation time) of SDS in aqueous solutions of sugars were also examined. The effect of different co-solvents viz. dimethyl sulfoxide (DMSO), methanol (MeOH) and dioxane on sugar-surfactant interactions has also been discussed and demonstrated in this paper.

Osmotic properties of carbohydrate aqueous solutions

Precise systematic osmotic coefficient measurements have been carried out for aqueous solutions of different carbohydrates and polyols by using vapor pressure osmometry (VPO) method. Herein, in order to investigate the effect of structure and stereochemistry of solutes on the vapor–liquid equilibria behavior of aqueous solutions, we studied the osmotic properties of binary aqueous sugar solutions containing pentose monosaccharides (xylose, ribose and arabinose), hexose monosaccharides (glucose, fructose, galactose and mannose), disaccharides (sucrose, maltose and lactose), trisaccharide (raffinose) and polyols (sorbitol, xylitol and maltitol) at 308.15 K and in the extended concentration range. From the experimental osmotic coefficient data, the values of water activity and vapor pressure of the investigated solutions were obtained.

Application of SAFT‐VR Equation of State for Prediction of Thermophysical Properties of Sugar Solutions

AbstractThe thermodynamic properties of sugar solutions, which are important solutions in food industries, have been calculated. Because of the large molecules and hydrogen bonding in the water/sugar solutions, the statistical association fluid theory of variable ranged (SAFT‐VR) equation of state was used to calculate the thermodynamic properties such as water activity, solubility, vapor pressure and boiling temperature of the aqueous sugar solutions, including glucose, sucrose and fructose. The SAFT‐VR parameters were calculated using vapor pressure and density data for water and water activity data for sugars. The total average absolute deviation percentage (AAD%) for all the calculated properties was 1.93%. The results showed that the model can accurately predict the properties of the sugar solution.Practical ApplicationsSugar solutions have important roles and uses in different industries such as food production, food preservation industries, chemical feed stock, pharmaceutical industries, metabolic reactions, industrial operations and chemical processes, such as crystallization, evaporation and selective separation. For example, water activity in a solution can be used to stop deteriorative reactions. The density of the solution is important in separation processes and mixing equipment. Solubility of sugar in water is another important property in food preservation and processes such as gasification and separation. The boiling temperature of the solution is an important thermodynamic property in different industrial processes such as purification and separation processes.

Separation of the acid‐sugar mixtures by using acid retardation and further concentration of the eluents by using continuous‐effect membrane distillation

AbstractBACKGROUNDA major cost in acid‐catalysed hydrolysis of biomass to fermentable sugars is the consumption of acid itself. In this study, a combined process was developed in which the acid and sugar in the hydrolysate were separated using an acid retardation process and then the dilute aqueous product streams were concentrated using a continuous‐effect membrane distillation (CEMD) process, thus acid could be reused as catalyst.RESULTSThe recovery rate of sugar was as high as 94.3–99.2% while the recovery rate of sulfuric acid was 92.4–98.9%. The eluents were further concentrated using the CEMD process. When a solution of 2 wt% sulfuric acid was concentrated to c. 40 wt%, the maximum value of permeation flux (Jw) and gained output ratio (GOR) was 6.20 L m−2 h−1 and 15.50, respectively. Meanwhile, the dilute aqueous sugar solution obtained from corn stover was concentrated 20‐fold to a final concentration of c. 497.6 g L−1 using the CEMD process with a final GOR of 5.5.CONCLUSIONThe combination of acid retardation and CEMD is suitable for the production of sugar, further purification and concentration of eluents; the sugar solution can be used for fermentation and acid solution can be reused as catalyst. © 2015 Society of Chemical Industry

Fabrication of carbon nanowires by pyrolysis of aqueous solution of sugar within asbestos nanofibers

Carbon nanowires have been fabricated by pyrolysis of an aqueous solution of sugar in nanochannels of asbestos fibers. Electron microscopy demonstrates that the diameter of these nanochannels corresponds to the diameter of the thinnest of the carbon nanowires obtained. Some of these nanowires have a graphite crystal lattice and internal pores. After asbestos is etched out, the carbon nanowires can retain the original shape of the asbestos fibers. Heating in an inert atmosphere reduces the electrical resistivity of the carbon nanowires to ∼0.035 Ω cm.

An approach to obtain the heat transfer coefficient of aqueous sucrose solutions in agitated boiling vessels

In this study, the heat transfer mechanism under agitated pool boiling was examined experimentally. Aqueous sugar solutions were used in a centrically agitated vessel. The effects of the gap which is between the impeller edge and the flat bottom of the agitated vessel, the rotational impeller speed and impeller size were studied on the boiling heat transfer coefficient. A new Nusselt function depending on the Peclet number was suggested for the heat transfer mechanism.

A femtosecond mid-infrared study of the dynamics of water in aqueous sugar solutions.

We study the effect of the sugars glucose, trehalose and sorbitol on the reorientation dynamics of water molecules, using polarization-resolved femtosecond infrared spectroscopy. We find that at all sugar concentrations the water dynamics can be described by a single reorientation time constant. With increasing carbohydrate concentration, the water reorientation time constant increases from 2.5 picoseconds to a value of about 15 picoseconds. The slowing down of the water dynamics is strongest for trehalose, followed by glucose and sorbitol.

Removal of Acid Beverage Flocs in Crystal Sugar by Adsorption Column Chromatography: Preliminary Study with Adsorbent Resin

The sugar industry has been facing some problems with white sugar intended for soft drinks production. Some studies have been demonstrated the sugar could be source of insoluble substances technically called by Acid Beverage Flocs (ABF). It appears during the beverage production; however, the flocs are easily disappearing with shaking. This may be related to raw material the sugarcane quality and, consequently, with the efficiency of the juice clarification process, since if there is no adequate juice treatment. The sugarcane commonly has lower quality and higher intensity of impurities, such as proteins, wax, minerals and colloids. The sugar industries are implementing solutions to reduce the amount of impurities through using technologies like ionic resins to removal of color, odor or undesirable taste. It could transform raw sugar in refined or white sugars. The aim of this work was evaluate the efficiency of purification of sugar solution with chromatographic adsorption system. We observed that the color reduction was around 69% and an intensive reduction in turbidity of sugar aqueous solution. There were variation on sucrose and increase on reducing sugars (glucose and fructose) contents. It is possible to conclude that the process could be efficient to reduce the color (MAU color), turbidity and ABF into sugar solutions.

Development of a native Escherichia coli induction system for ionic liquid tolerance.

The ability to solubilize lignocellulose makes certain ionic liquids (ILs) very effective reagents for pretreating biomass prior to its saccharification for biofuel fermentation. However, residual IL in the aqueous sugar solution can inhibit the growth and function of biofuel-producing microorganisms. In E. coli this toxicity can be partially overcome by the heterologous expression of an IL efflux pump encoded by eilA from Enterobacter lignolyticus. In the present work, we used microarray analysis to identify native E. coli IL-inducible promoters and develop control systems for regulating eilA gene expression. Three candidate promoters, PmarR’, PydfO’, and PydfA’, were selected and compared to the IPTG-inducible PlacUV5 system for controlling expression of eilA. The PydfA’ and PmarR’ based systems are as effective as PlacUV5 in their ability to rescue E. coli from typically toxic levels of IL, thereby eliminating the need to use an IPTG-based system for such tolerance engineering. We present a mechanistic model indicating that inducible control systems reduce target gene expression when IL levels are low. Selected-reaction monitoring mass spectrometry analysis revealed that at high IL concentrations EilA protein levels were significantly elevated under the control of PydfA’ and PmarR’ in comparison to the other promoters. Further, in a pooled culture competition designed to determine fitness, the strain containing pPmarR’-eilA outcompeted strains with other promoter constructs, most significantly at IL concentrations above 150 mM. These results indicate that native promoters such as PmarR’ can provide effective systems for regulating the expression of heterologous genes in host engineering and simplify the development of industrially useful strains.

Calorimetric and molecular simulation study on unfrozen water characteristics in aqueous sugar solutions: implications for biopreservation

Intensive studies have been conducted to determine the protective mechanisms of sugars that have proven beneficial to the biopreservation application. However, little has been known about the unfrozen water content that aqueous sugar solutions can possess when frozen at cryogenic temperatures. This study conducted calorimetric measurements to determine the unfrozen water content in frozen aqueous solutions of glucose, fructose, sucrose and trehalose of multiple concentrations. The hydrogen-bonding network in these solutions was characterised by molecular simulations. The experimental results showed that more water could be prevented from ice crystallisation in a more concentrated solution. Disaccharides, especially trehalose, are more effective than other protectants (e.g., glucose, glycerol and dimethyl sulfoxide) for detaining water in the unfrozen state. Moreover, it was found that, at molecular levels, there were more hydrogen bonds between sugar and water molecules in a more concentrated solution. From both macro- and microscopic perspectives, trehalose was demonstrated to be a much more effective cryoprotectant than others. This comparative study proved that the unfrozen water should be mainly attributed to hydrogen bonds between sugar and water in the mixture. Our findings will provide valuable information for determining the physical state of cryopreserved biomatrix and guiding the preparation of protective formulations.

Isothermal dehydration of thin films of water and sugar solutions

The process of quasi-isothermal dehydration of thin films of pure water and aqueous sugar solutions is investigated with a dual experimental and theoretical approach. A nanoporous paper disk with a homogeneous internal structure was used as a substrate. This experimental set-up makes it possible to gather thermodynamic data under well-defined conditions, develop a numerical model, and extract needed information about the dehydration process, in particular the water activity. It is found that the temperature evolution of the pure water film is not strictly isothermal during the drying process, possibly due to the influence of water diffusion through the cellulose web of the substrate. The role of sugar is clearly detectable and its influence on the dehydration process can be identified. At the end of the drying process, trehalose molecules slow down the diffusion of water molecules through the substrate in a more pronounced way than do the glucose molecules.