Glucose Concentration In Solution Research Articles

THEORETICAL DETERMINATION OF SORPTION ISOTHERMS APPLIED TO PROCESS CHESTNUT WITH OSMOTIC PRE-TREATMENTS BASED ON ITS CHEMICAL COMPOSITION

Sorption isotherms for fresh chestnut and particularly processed chestnut with osmotic treatments using sodium chloride, glucose and sucrose solutions of different concentrations (22.0%, 56.5%, and 60% w/w, respectively) were predicted at 25°C by means of a simplified prediction algorithm of water sorption isotherms. This model is based on the composition of the main compounds of foods (glucose, fructose, sucrose, salt, protein, fibre and starch). The processed chestnut composition changed significantly by the addition of salts and sugars. The processed chestnut sorption isotherm was theoretically predicted with the same accuracy as the chestnut fresh isotherms. Using the prediction model the equilibrium moisture content could be calculated for the assayed systems with a correlation coefficient (R 2 ) of (>0.989), a mean relative error (E) of (<4.40%) and a standard error (E RMS ) of (<0.049 kg (kg d.b.) -1 ).

Production and characterization of lipid microparticles produced by spray cooling encapsulating a low molar mass hydrophilic compound

The objective of this research was to produce and characterize lipid particles (MpLs) that may be used as carriers of high amounts of hydrophilic core and evaluate the influence of the core amount on the performance of lipid microparticles. The MpLs were produced by spray cooling from solid and liquid lipid mixtures (stearic and oleic fatty acids and partly hydrogenated vegetable fat) containing glucose solution as core and soy lecithin as surfactant. The performance of MpLs was evaluated by means of the effective amount of encapsulated core, the core amount present on the surface of MpLs (superficial glucose) and the core release profile in aqueous solution. Morphological observations showed that MpLs presented spherical shape and a rugged and continuous surface, and an average diameter between 25 and 32 µm. The effective amount of encapsulated core was greater than 78% for all formulations evaluated. Larger amounts of superficial glucose were found in formulations in which more concentrated glucose solutions were used, regardless of the glucose lipid-solution ratio. The release results showed that core retention was significantly influenced by the glucose solution concentration, whereas release modulation was influenced by the glucose lipid-solution ratio.

Flexible glucose sensor with biocompatible polymer substrate

In this study, a flexible glucose sensor with biocompatible polymer substrate for biomedical measurement was constructed and tested. The sensor was constructed by immobilizing an enzyme to biocompatible polymer substrate with electrodes. In the fabrication of the sensor, Pt-working and Ag/AgCl-counter/reference electrodes were formed onto a flexible polymer substrate by MEMS technique. In the immobilization process of an enzyme, a mixture solution of glucose oxidase (GOD) and PMEH as a biocompatible polymer was spread onto the sensing region of the electrodes, thus obtaining the flexible glucose biosensor with biocompatibility. In the evaluation of the sensor characteristics, the sensor was dipped into a measurement cell filled phosphate buffer, and then a +400mV potential was applied to Pt-working electrode vs. Ag/AgCl-counter/reference electrode by potentiostat controlled by PC. Various concentrations of glucose solution were dropped into the beaker and the output current of the sensor was measured by PC via A/D converter. As a result of characteristics evaluation, the output current rapidly increased immediately after the drop of glucose solution and linearly corresponded to glucose concentration over a range of 0.05-4.0mmol/l, with a correlation coefficient of 0.999. The result suggests that GOD was successfully immobilized onto the substrate. This sensor would be applied to detecting tear glucose of rabbit for continuous evaluation of blood sugar level in the near future.

Dynamics of Sedimentation and Deformation of GUVs Under Different Tonicity Conditions

POPC Giant unilamellar vesicles (GUVs) with 1 mol% DiIC18(3) as a fluorescent marker were prepared by electroformation in sucrose solutions with varying osmolarities. These vesicles were resuspended in glucose solutions of different concentrations generating isotonic and hypertonic conditions. Vesicles sediment due to the density difference between the solutions. The movement of the vesicles as they approach the glass surface is studied using SPIM microscopy. We find that the velocity of the GUVs remains constant, given by Stokes law as expected when the distance from the surface is several radii in length. Velocity decreases exponentially as vesicles reach the surface. Vesicle deformation due to interactions with the surface was measured for different osmotic conditions using confocal and SPIM microscopy. Boundary element simulations were performed to model vesicle deformation during sedimentation within a viscous fluid. For isotonic conditions, vesicles are assumed to begin with zero tension and tension is generated through contact with the surface. For the hypertonic case, the same is true but with an initial excess area available. Computationally, the mechanical behavior of the lipid bilayer is simulated using a model that considers two modes of deformation responsible for increases in area strain. The first is the smoothing of suboptical thermal undulations and the second is the direct stretching of the area per lipid molecule. Properties of the lipid bilayer are controlled by adjusting bending and area compressibility moduli. A force field is implemented that takes into account local tension, local curvature force, and gravitational pull. Vesicle sedimentation, deformation, and membrane tension were evaluated as a function of g0, a dimensionless factor relating gravitational and curvature energies. Simulations are in agreement with the experimental results and provide additional information of the deformation of vesicles and sedimentation dynamics.

A Microwave Dielectric Biosensor Based on Suspended Distributed MEMS Transmission Lines

Design and characterization of a miniature microwave dielectric biosensor based on distributed microelectromechanical systems (MEMS) transmission lines (DMTL) is reported in this paper. The biosensor has been realized by bonding the DMTL device with an acrylic fluidic channel. In order to demonstrate the sensing mechanism, the sensor is used to detect the small variation of the concentration of aqueous glucose solutions by measuring the electromagnetic resonant frequency shift of the device. It is observed from the results that the second notch of the reflection coefficient (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) varies from 7.66 to 7.93 GHz and the third notch of the reflection coefficient varies from 15.81 to 15.24 GHz when the concentration of the glucose solution ranges from 0 to 347 mg/ml, which indicates that higher order notches have higher sensitivities if looking at the absolute change in frequency.

IMPROVE THE DATA ACQUISITION SYSTEM OF A QCM SENSOR BY INCREASING THE SAMPLING RATE OF FREQUENCY AND AMPLITUDE

Quartz crystal microbalance (QCM) has been constructed and used for chemical sensing and biochemical detecting. Frequency shift has a relation with mass changed in the gaseous condition. However, the velocity, density, and viscosity also cause frequency changed in liquid solution. We develop a new method and system to investigate the variable value of amplitude and frequency from the oscillator of quartz. In this system, piezoelectric quartz crystal (10 MHz, AT-cut) with gold electrodes was mounted under liquid solution. Crystal was exposed to the different concentrations of glucose and sodium chloride solution. The results show that the ramp-up speed of amplitude was faster as frequency in the alternative state. We figure out the largest skew through the differential curve of amplitude in different solutions. The dramatic results give a QCM more meanings to be a biochemistry detecting utility.

Preparation of short, robust and highly ordered TiO2 nanotube arrays and their applications as electrode

The short, robust and highly ordered TiO2 nanotube arrays (TNAs) electrode was prepared by sonoelectrochemical anodization of titanium in HF–H2O electrolyte solution (referred as short TNAs, STNAs). The self-organized arrays of titania nanotubes of approximately 12–65nm in diameter and 75–280nm in length can be synthesized at anodic voltage of 5–20V. The electron transport process within the STNAs electrode was much favorable in comparison with that for the long TNAs electrode synthesized by conventional magnetic agitation technique (referred as long TNAs, LTNAs), as confirmed by the obviously enhanced photocurrent response of STNAs electrode either in 0.02M Na2SO4 electrolyte solution or in different concentrations of glucose solution or under different intensities of UV illumination. To investigate their photoelectrochemical applications, degradation of tetracycline, a typical pharmaceutical and personal care products (PPCPs), was carried out using photoelectrocatalytic (PEC) means, comparing with electrochemical (EC) and photocatalytic (PC) processes. The kinetic constant of the PEC process of STNAs electrode was ∼3.17 times as high as its PC process. The color removal rate of tetracycline by STNAs electrode achieved 81% within 3h, which was 21% higher than that for LTNAs electrode. In degrading tetracycline, 41% of TOC was mineralized using the STNAs electrode against 23% using LTNAs electrode under similar conditions. Such kind of titania nanotubes will have many potential applications in various areas as an outstanding photoelectrochemical material.

Interplay between Solvent Effects of Different Nature in Interfacial Bond Breaking Electron Transfer

Solvent dynamics effects on electroreduction of peroxodisulphate anion on mercury electrode (a typical bond breaking electron transfer reaction) are explored in the framework of the Sumi-Marcus model. The reaction three-dimensional free energy surface is constructed using the Anderson model Hamiltonian. A new interpretation of short- and long-time survival times is presented as well. Since the reduction is assumed to proceed from aqueous sucrose and glucose solutions of different concentrations (which are used to vary the solution viscosity), unavoidable changes in the Pekar factor (static effect) are also taken into account. The results of model calculations are employed to interpret challenging experimental data on nonmonotonous constant rate vs solution viscosity dependence reported earlier (in part, appearance of an ascent plot). The influence of mixed solvent composition on the reaction rate and transfer coefficient is explained in terms of the saddle point avoidance in the vicinity of activationless discharge. Splitting of the reaction coordinates into slow (solvent) and fast (intramolecular) ones is argued to be crucial, as the most important reaction features cannot be described by means of more simplified models, even if both static and dynamic effects are addressed.

A New Application of Thermal Spray in Preparation of Metallic Membrane for Concentration of Glucose Solution

Wire arc spraying has recently been used for preparation of porous metallic membranes. This work focuses on characterization of the metallic membranes produced by this technique based on porosity, oxide content, and the pore size distribution. The effect of atomizer air pressure and stand-off distance on membrane properties is examined. According to the obtained results, stronger atomizer air pressure leads to a decrease in both porosity and oxide content, while a longer stand-off distance promotes the oxide content and only increases the porosity at the distances not longer than 30 cm. A prepared metallic layer was set up in an experimental membrane cell as a permselective film for filtration of glucose solution. Generally, the water flux was appropriate, and the prepared membranes was able to remove glucose from water efficiently.

New innovative gold catalysts prepared by an improved incipient wetness method

We described 0.3% Au/Al 2O 3 catalysts prepared by the incipient wetness impregnation method using hydrogen tetrachloroaurate dissolved in different aqueous solutions as an impregnation solution. Hydrogen tetrachloroaurate hydrolyses in aqueous solution and the composition of the gold complexes depend on the pH value and the chloride concentration; therefore, different impregnation solutions were prepared by dissolving the hydrogen tetrachloroaurate in water and aqueous solutions of hydrochloric acid, nitric acid, sodium chloride, and sodium hydroxide. The resulting gold complexes were evaluated by UV/vis spectroscopy. Gold catalyst precursors were activated via gas-phase reduction with hydrogen. In addition, the catalyst precursors and the catalysts were investigated by TPR and TEM analysis, respectively, and tested in glucose oxidation. The gold catalyst prepared with a hydrochloric acid solution exhibited the highest activity in glucose oxidation and the smallest gold particles (mean diameter, 1–2 nm). In fact, the catalysts prepared from precursor solutions in which the tetrachloroaurate ion was stabilized demonstrated the highest activities. This is a significant finding, because residual chloride in the catalyst precursor has been considered detrimental to the preparation of active catalysts. In addition, the gold catalyst prepared with 2 M HCl was tested in repeated batches and exhibited excellent long-term stability for the conversion of highly concentrated glucose solutions.

Microring-resonator-based sensor measuring both the concentration and temperature of a solution

We propose and investigate experimentally a micro-ring-resonator-based sensor with which we can measure both the concentration and temperature of glucose solution. It consists of two micro-ring resonators consecutively coupled to a bus waveguide by the overlap between them. The resonance wavelengths of the two resonators change similarly with the temperature but differently with the concentration. For that purpose, the core of just one micro-ring resonator is exposed directly to the solution. Using polymers, conventional processes, and a polymer lift-off process, we implement the sensor. Through the measurement of the fabricated sensor, we obtain its characteristics of measuring the temperature and concentration.

Production of a potentially probiotic culture of Lactobacillus casei subsp. casei CECT 4043 in whey

Batch and fed-batch fermentations for the production of a highly concentrated culture of Lactobacillus casei CECT 4043 were carried out in whey-based media. In batch fermentation, the maximum concentrations of biomass (0.33 g L −1) and antibacterial activity (3.42 AU mL −1) were obtained in diluted whey medium (2% w/v lactose, initial pH 7.0) after 12 h. Based on these results, biomass and antimicrobial metabolites production in two re-alkalized fed-batch fermentations were carried out in diluted whey medium. The first fed-batch culture was fed with concentrated whey (5% w/v lactose) and a 400 g L −1 concentrated lactose solution. The second culture, which was fed with a concentrated mussel processing waste (10% w/v glucose) and a 310 g L −1 concentrated glucose solution, provided the highest concentrations of biomass (1.7 g L −1), viable cells (∼1.7 × 10 10 cfu mL −1), lactic acid (27.8 g L −1), acetic acid (3.9 g L −1) and antibacterial activity (74.2 AU mL −1).

Intra- and extra-cellular organophosphorus hydrolase production with recombinant E. coli using fed-batch fermentation

A fed-batch fermentation process for the production of organophosphorus hydrolase (OPH) (EC 3.1.8.1) by E. coli pET812 was developed in this research. With batch fermentation, the maximum OPH concentrations attained by batch fermentation were as low as 4 × 105 U/l because cell growth and OPH production were inhibited by a high initial concentration of glucose. To develop a fed-batch fermentation process for obtaining higher concentrations of OPH, highly concentrated glucose solution (500 g/l) was added intermittently or continuously to increase the carbon source concentration. Eventually, 3.2 × 106 U/l of OPH was produced with fed-batch fermentation in 24 h. This was eight times higher than the yield with conventional batch fermentation. A total concentration of 399–441 mg of OPH was produced/l, which was four times higher than that reported when using E. coli. Nearly half (44%) of the produced OPH was secreted into the culture solution.

The osmotic link between hypoglycaemia and hypovolaemia

Objective. Hypoglycaemia is regularly accompanied by hypovolaemia. To suggest a mechanism for this phenomenon, we reviewed data from eight studies conducted by our group and examined the circumstances under which rebound hypoglycaemia develops after intravenous infusion of glucose solutions. Material and methods. Forty healthy volunteers and 40 patients received a total of 122 infusions of glucose solutions at different rates, volumes and concentrations. Plasma glucose and the haemodilution were measured repeatedly during and for at least 2 h after the infusions ended. Glucose kinetics was calculated using a one‐compartment turnover model and the plasma volume expansion was estimated from changes in Hb. Results. A strong linear correlation was found between the glucose level and the plasma volume expansion in all series of experiments (p<0.001). After infusion, there was a risk of hypoglycaemia and hypovolaemia developing in healthy volunteers with a high glucose clearance and when infusing glucose solutions of higher concentrations than 2.5 %. Few and mild hypoglycaemic events occurred in patients with insulin resistance, such as in diabetics and in those undergoing surgery. The immediate linear relationship between hypoglycaemia and hypovolaemia suggests an osmotic link between the two parameters. More specifically, infused fluid accompanies glucose during uptake into the cells, while volume expansion by the same fluid has already elicited an effective diuretic response. Conclusion. Hypovolaemia is a consequence of hypoglycaemia after intravenous infusion of glucose solution and is caused by the osmotic translocation of fluid from the extracellular to the intracellular fluid space that occurs despite effective renal elimination.

A Simple Substrate Feeding Strategy using a pH Control Trigger in Fed-Batch Fermentation

A simple automated glucose feeding strategy based on pH control was developed to produce high-cell-density fed-batch fermentation. In this strategy, the pH control scheme utilized an acidified concentrated glucose solution to lower the pH. The frequency of glucose addition to the fermentor is determined by the culture's growth kinetics. To demonstrate the effectiveness of the coupled pH and glucose control strategy in biomass and/or secondary metabolite production, several fed-batch fermentations of indigenous Escherichia coli and recombinant E. coli were carried out. Both strains produced biomass with optical density of greater than 40 at 600 nm. We also tested the glucose control strategy using two types of pH controller: a less sophisticated portable pH controller and a more sophisticated online proportional-integral-derivative (PID) controller. Our control strategy was successfully applied with both controllers, although better control was observed using the PID controller. We have successfully demonstrated that a glucose feeding strategy based on a simple pH control scheme to indirectly control the glucose concentration can be easily achieved and adapted to conventional bioreactors in the absence of online glucose measurement and control.

The energy challenge of direct contact membrane distillation in low temperature concentration

AbstractDirect contact membrane distillation (DCMD) was operated at low temperatures from 25 to 40 °C to suit the purpose of thermally concentrating sensitive liquid foods, especially fruit juices to high solid content concentrate with most of the quality attributes preserved.A lab scale DCMD unit has been set up at the Centre for Plant and Food Science, University of Western Sydney. Hollow fibre modules (HFM) using five types of fibres of polyvinylidene fluoride (PVDF) and Halar material, with mass transfer areas ranging from 281 to 573 cm2 were employed. Experiments for concentration of glucose solutions from 30 to 60% (w/w) were carried out. Results indicated that not only the operating conditions were important, but also the membrane properties. It was found that Halar fibres were performing 2–3 times better than PVDF fibres in term of removing water from the feed, and 3–4 times better in term of energy saving. Results also showed that an increase of the feed inlet temperature from 25 to 40 °C improved the mass flux up to 6 times and energy efficiency (EE) up to 2.5 times depending on the feed concentration.With flux up to 2.88 kg m−2 h−1 for PVDF and 5.83 kg m−2 h−1 for Halar fibres when concentrating 30% glucose solution at 40 °C, DCMD appeared to be an attractive concentration technique, when product quality is the priority. However, with EE from as low as 2.1–14.9%, PVDF fibres employed in the study seemed not to be very suitable for DCMD liquid food concentration under low temperature condition. DCMD in Halar fibres with EE up to 45.6% still encounters the challenge of energy and could only be cost competitive to osmotic distillation and evaporative concentration when cheaper energy sources or heat recovery measures are employed. Copyright © 2007 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Technical note: Kinetics of sorbic acid loss during storage of peaches preserved by combined factors

It was found that the loss of sorbic acid in stored peaches preserved by combined factors (water activity, pH, additives) followed first order reaction kinetics. Rate constants and activation energy (14 kcal/mol) were almost identical to those previously reported for sorbic acid loss in concentrated glucose solutions of identical water activity and pH.

Influence of solid loading on enzymatic hydrolysis of steam exploded or liquid hot water pretreated olive tree biomass

Olive tree pruning biomass, pretreated by either liquid hot water or steam explosion under selected conditions, was used as a substrate for enzymatic hydrolysis. The pretreated material was further submitted to alkaline delignification, the objective being to improve hydrolysis yields as well as increasing cellulose content in the pretreated feedstock. The enzymatic hydrolysis of pretreated residues was performed using a commercial cellulase mixture supplemented with β-glucosidase, using a solid loading range from 2 to 30% (w/v). The influence of substrate concentration on the enzymatic hydrolysis yield and on glucose concentration was studied. Comparative results with and without a delignification step are presented. Enzymatic hydrolysis at high substrate concentration (≥20%) is possible, yielding a concentrated glucose solution (>50 g/L). Nevertheless, a cellulose fraction of the pretreated residue remains unaltered.

The Role of Operating Conditions in Osmotic Distillation and Direct Contact Membrane Distillation - A Comparative Study

This paper presents a comparative study on the role of operating conditions in osmotic distillation (OD) and direct contact membrane distillation (DCMD). Comparisons were made for lab scale OD and DCMD experiments on two types of PVDF hollow fibres under similar operating conditions for the concentration of glucose solutions from 30 to 60% (w/w) at temperatures as low as 25 to 45°C. Analysis of the results indicated that temperature was the most influencing factor for process improvement for both OD and DCMD. The flux in DCMD was improved by 3 to 4 times when feed temperature increased by 15 degrees, while this figure was nearly 3 times for OD when feed temperature increased by 20 degrees. The flow rates of the two streams played a more important role in maintaining the driving force, and consequently the flux rate, in DCMD rather than in OD. It was found that feed velocity had significant effect on DCMD performance, but insignificant in OD. Feed concentration, as the determining factor on water activity and viscosity, caused a more serious reduction of the flux rate in the high concentration range of 45-60% rather than in the dilute region of 30-40%. The effect was more significant in DCMD than in OD. The ratio of DCMD flux over that of OD ranged from 0.41 to 0.66 for PV375 when concentrating glucose solutions 30-40% w/w and from 0.35 to 0.69 for PV650 when concentrating high solid content ones. However, DCMD can overcome the disadvantages of OD being poor consumers’ perception, (due to the use of brine solution being a chemical), the potential problem of corrosion by the brine and the cost of its reconcentration.

Extension of Einstein's viscosity equation to that for concentrated dispersions of solutes and particles

A viscosity equation for concentrated solutions or suspensions is derived as an extension of Einstein's hydrodynamic viscosity theory for dilute dispersions of spherical particles. The derivation of the equation is based on the calculation of dissipation of mechanical energy into heat in the dispersion, subtracting the energy dissipation in the portion of solutes or particles. The viscosity equation derived thus was well fitted to the viscosity-concentration relationship of the concentrated aqueous solutions of glucose and sucrose. For the suspensions of bakers' yeast, the concentration dependency of viscosity was expressed well with some modification for the flow pattern around suspended particles. It is suggested that these viscosity equations can be widely applied to both diluted and concentrated dispersions of various solutes and particles.