Diffusion Coefficient Of Glucose Research Articles

Glucose fast-response amperometric sensor based on glucose oxidase immobilized in an electropolymerized poly(o-phenylenediamine) film

o-Phenylenediamine has been used for glucose oxidase (GOx) immobilization on Pt electrodes by electrochemical polymerization at +0.65 V vs SCE. By this approach the enzyme is entrapped in a strongly adherent, highly reproducible thin membrane, whose thickness is around 10 nm. This one-step procedure produces a glucose sensor with a response time less than 1 s, an active enzyme loading higher than 3 units/cm2 of electrode surface, a high sensitivity, and a sufficiently wide linear range. The glucose response shows an apparent Michaelis-Menten constant, K'm = 14.2 mM, and a limiting current density, jmax of 181 microA/cm2. The product kD of partition and diffusion coefficients of glucose in the polymer film is on the order of 10(-13) cm2/s. Due to permselectivity characteristics of the membrane, the access of ascorbate, a common interfering species, to the electrode surface is blocked. To our knowledge, this represents the first report of a membrane capable, at the same time, of immobilizing GOx and rejecting ascorbate. The interesting electrode behavior can be rationalized by using an existing model predicting the amperometric response of an immobilized GOx system.

Diffusion in immobilized-cell agar layers: influence of microbial burden and cell morphology on the diffusion coefficients ofl-malic acid and glucose

The diffusivities ofl-malic acid and glucose in an agar membrane entrapping small amounts ofEscherichia coli orRhodospirillum rubrum whole cells were measured using time lag (TL) and steady state (SS) methods. Diffusivities were overestimated by the SS method. For concentrations of immobilizedR. rubrum cells ranging between 104 and 109 organisms cm−3 agar (20 ng-2 mg dry weight cm−3 agar), the diffusion coefficient ofl-malic acid, determined by both methods, was related to the logarithm of the membrane cell content by a decreasing linear relationship. The diffusion coefficient of glucose obtained by TL analysis was not significantly affected by the presence in the membrane of 3 ng-0.3 mg dry wt.E. coli cm−3 agar. However, values arising from the SS method decreased linearly as a function of the amount of immobilized organisms. Membranes containingR. rubrum cells offered higher diffusional resistance tol-malic acid and glucose than those loaded with the same amount ofE. coli cells.

Evaluation of some gelling agents for immobilization of aerobic microbial cells in alginate and carrageenan gel beads

Different gelling agents were used to immobilized viable cells in either alginate or κ-carrageenan gel beads. Based on cell leakage from the gel beads, oxygen and glucose diffusion coefficients and toxicity of the gelling agents, SrCl2 was found to be the best for immobilization of aerobic microbial cells in, not only alginate but also carrageenan gel beads.

Diffusion Coefficients of Glucose, Potassium, and Magnesium in Maine Russet Burbank and Maine Katahdin Potatoes from 45 to 90°C

ABSTRACTExperimental data for the leaching of glucose, potassium and magnesium from French fry cut Maine Russet Burbank and Maine Katahdin potatoes were modeled over the temperature range 45–90°C., using a one‐parameter diffusion equation based on Fick's second law. Correlations for the dependence of the resulting effective diffusion coefficients on temperature were determined. At temperatures greater than 60°C., plots of the diffusion coefficients as a function of temperature showed a change in slope or a discontinuity in the slope of the curve. This reflected the change in the diffusion matrix which occurred when the starch began to gelatinize. The effect of cultivar differences on values of the diffusion coefficients might be linked to the concentrations of starch and electrolytes in the potato.

Chromatographic evaluation of sorption and diffusion characteristics of glucose, maltose and maltotriose in silica gels

Liquid chromatographic techniques were employed to evaluate the sorption and diffusion characteristics of glucose, maltose and maltotriose in silica gel. The equilibrium constants were found to decrease with increasing molecular size. The determined diffusion coefficient of glucose is comparable to that in the literature. The pore diffusivities decrease with increasing size of the carbohydrates at all temperatures.

コーングリッツ内部のグルコースとエタノールの拡散速度

Effective diffusion coefficients of glucose and ethanol in corn grits were estimated as a factor affecting the velocity of solid-state ethanol fermentation by using the Crank's equation. Experimental results showed values about 1/5 of the molecular coefficient in water. The 90% response time of diffusion was 5 to 10 minutes in well stirred solution. This means that the diffusion rates are evaluated to be larger than the rates of changes in solute concentration, and that effects of concentration distribution of these substances are negligible in the course of conventional solid-state ethanol fermentation of corn grits.

A new immobilization technique of whole cells and enzymes with colloidal silica and alginate

A mixed gel composed of colloidal silica and alginate (As gel) was prepared for the immobilization of enzymes or microorganisms. The physical strength of AS gel increased with the amount of colloidal silica. The ethanol production rate of Saccharomyces cerevisiae (IFO 0224) immobilized in AS gel was higher than in alginate gel (Al gel) in the early phase of growth. At a concentration of glucose of more than 10%, the ethanol production of immobilized yeast in AS gel was higher than in Al gel. Any difference was not recognized in the diffusion coefficient of glucose between AS and Al gels. The AS gel had an ability to retain proteins such as bovine serum albumin and gamma-globulin. The alkaline protease and beta-galactosidase in AS gel continued their function for a long time, but those immobilized in Al gel did not. Immobilized beta-galactosidase in AS gel had a higher thermal stability than in Al gel or free enzymes.

Measurement of effective diffusivities of ionic and non-ionic solutes through beef and pork muscles using a diffusion cell

A diffusion cell in conjunction with a new mathematical model was used to measure the apparent diffusion coefficients of sodium chloride, potassium nitrate and glucose through beef semitendinosus and pork longissimus dorsi muscles. The apparent diffusion coefficient was obtained within less than 180 min with a coefficient of variation less than 10% in most cases. The influence of temperature can be adequately explained by the Arrhenius-type law with activation energy between 19 and 26 kJ/mol depending on the diffusant. However, these values were not significantly different. Finally, we showed that the apparent diffusion coefficient of sodium chloride is not affected by the direction of the muscle fibre to the axes of diffusion while glucose diffusion parallel to the muscle fibre can be three times greater than diffusion at a right angle to the muscle fibre.

Effective Diffusion Coefficients in Calcium Alginate Gel

AbstractThe effective diffusion coefficient of glucose, De in calcium alginate gel determined at 35°C by two different methods gave values which, on average, were at least 24% less than in water. Assessment of the effect of glucose concentration on De seems to indicate that De increased with decreasing glucose concentration at very low concentrations (i.e., < =100 mM) and increased with increasing glucose concentrations at high concentrations (i.e., > =200 mM). Increasing the concentration of either the calcium chloride or sodium alginate component used in calcium alginate formation substantially decreased De, but the effect of sodium alginate was the greater of the two.

Determination of the effective diffusion coefficient of glucose in callus tissue

Immobilization of plant cells in reticulate foam matrices creates a milieu which is similar to that prevailing in callus tissues. Since many valuable plant secondary metabolites are found mainly in the callus as opposed to suspension cultures, there is considerable interest in immobilized plant cell cultures. In the design of bioreactors for such systems, there is a need to know the effective diffusion coefficients through the integral mass of the immobilized cells. In this work, diffusion of glucose through callus tissue was determined using 4C-labelled glucose. Application of one-dimensional unsteady state molecular diffusion theory to the experimental results indicated that the value of the effective diffusion coefficient was in the range (0.028 – 0. 28) × 10 −5 cm 2 s −1.

Diffusion of Glucose in Carrageenan Gels

ABSTRACTFrom an experimental set‐up with boundary conditions of an extended initial distribution the diffusion coefficient for glucose in a high K‐content carrageenan gel was evaluated as a function of the carrageenan concentration (1, 2 and 4%) and temperature (0.0, 5.0, 10.0, 15.0, 25.0, and 36.0°C). According to an Arrhenius‐type equation, the activation energies at 1, 2 and 4% of carrageenan were calculated as 18.1, 17.4, and 19.1 kJ/mol. From these data it was concluded that carrageenan affects diffusion mainly by an obstruction effect.

Diffusion in κ‐carrageenan gel beads

Using a well-mixed and temperature-led vessel, the diffusion characteristics of various solutes into spherical kappa-carrageenan gel beads were experimentally investigated. The diffusion coefficient of glucose was markedly affected by the glucose concentration and the operating temperature. In all cases the diffusivity obtained was noticeably smaller than that of glucose in pure water. The experimental data also indicated an inverse relationship between the diffusivity and the polymer concentration used in the gel preparation. As well, the glucose diffusivity was affected by the presence of other solutes in the glucose solution. Electrolytes such as ammonium sulfate, KCl, and CaCl(2) were observed to enhance the diffusion coefficient. On the other hand, the addition of arginine or bovine serum albumin had an adverse effect on the diffusivity. No diffusion of albumin into the gel beads was observed, and such a solute created a significant mass transfer resistance during the diffusion process.

Diffusion coefficients of glucose and ethanol in cell‐free and cell‐occupied calcium alginate membranes

The diffusivities of glucose and ethanol in cell-free and cell-occupied membranes of calcium alginate were measured in a diffusion cell. The lag time analysis was used. Diffusivities decreased with increasing alginate concentration and were comparable with those in water for a 2% alginate membrane. Glucose and ethanol concentrations had no effect on the respective diffusion coefficients. The ratio of ethanol diffusivity to glucose diffusivity in 2 and 4% alginate agreed closely with the inverse ratio of the hydrodynamic raii for the two molecules in water, indicating that the hydrodynamic theory of diffusion in liquids may be applicable to diffusion in dilute alginate gels. Also, the presence of 20% dead yeast cells had no effect on the diffusivities. The data reported can be used to study reaction and diffusion in immobilized cell reactors and cell physiology under immobilized conditions.

Diffusion of carbohydrates in anion exchangers

Selectivity problems may arise for the isomerization of sugars catalysed by ion-exchangers if diffusion becomes relatively slow. Therefore, experiments were carried out to determine the diffusion coefficients of glucose in a gel type (IRA 401) and a macroreticular type (IRA 938) of ion exchanger. Formulae are given that correlate diffusivity with sugar concentration, temperature and polymer fraction of the ion-exchanger.

The glucose distribution in 9L rat brain multicell tumor spheroids and its effect on cell necrosis.

The glucose consumption rate of 9L rat brain tumor cells was determined as a function of concentration. Glucose uptake followed Michaelis-Menten kinetics with a Km of 0.58 mM and a Vmax of 1.6 pg/cell-min. The glucose diffusion coefficient in spheroids of 9L tumor cells was determined to be 1.5 x 10(-6) cm2/s at 37 degrees C. Using these parametric values, the glucose distribution in 9L multicell spheroids was calculated and related to the viable and necrotic zones.

Diffusion into microbial aggregates

Theoretical work in the biological waste treatment field has been directed at modeling substrate removal processes in fluidized and fixed film microbial systems in terms of the basic rate processes. Much of the research has been directed at delineating the rate limiting steps to simplify the problem. Various researchers have shown that the rate limiting step can be mass transfer through the microbial aggregate to the active sites at the cells. Therefore, any mechanistic model that incorporates mass transfer must be sensitive to variations in the reactant diffusion coefficient through floc material. A direct measure of mass flux has been developed to determine the variations in the diffusion coefficients of glucose and oxygen through microbial aggregates grown under various experimental conditions. A factorial analysis indicated significant changes in the molecular diffusion coefficient with variations in sludge age and carbon-nitrogen ratio in the growth media. Oxygen diffusivity varied from 20 to 100% of its value in water, glucose from 30 to 50%. A simple zero order diffusion-reaction kinetic model for spherical floc was constructed. It indicated that oxygen diffusion limitations are possible in the high rate activated sludge processes with large floc particles.

The Movement of Glucose and Glycine Through the Tissues of Corymorpha Palma Torrey (Coelenterata, Hydrozoa)

ABSTRACT The rate of diffusion of 14C-labelled glucose and glycine across isolated mesogloea and across the mesogloea and cell layers of the large solitary hydroid, Corymorpha was measured. Diffusion coefficients of glucose and glycine in mesogloea were found to be about 16 times lower than their values in water and of the same order as their values in dialysis tubing and Millipore filters,

THE PERMEABILITY OF ARTICULAR CARTILAGE

1. We have shown that the permeability of cartilage is the same in necropsy specimens as in the living animal. We have concluded that studies of material transport into cartilage carried out on necropsy specimens validly reflect in vivo conditions. 2. We have studied the effect of agitation of the fluid in which cartilage is immersed upon the rate of diffusion of substances into cartilage and have found that agitation increases the rate of penetration up to three or four fold. We believe that it may be inferred from this fact that the nutrition of cartilage is partly dependent on joint movement. 3. We have examined the permeability of the bone-cartilage interface to water and solutes and have found that in the adult no detectable material transfer occurs across this zone. In the child on the other hand the bone-cartilage interface appears to be permeable to water and solutes. 4. We have measured the diffusion coefficient of glucose in cartilage and have hence estimated the depth of cartilage which can be adequately supplied with glucose from the synovial fluid in the presence and absence of agitation. 5. We have examined both experimentally and theoretically the possible effect of intermittent loading on the rate of penetration of substances into cartilage. We have concluded that at low pressures intermittent loading contributes little to the material transfer into cartilage. At high pressures intermittent loading does lead to the transport of solutes into cartilage but it cannot significantly increase the rate of transfer above that attributable to normal diffusion. Loading cartilage surfaces for prolonged periods of time without allowing intermittent relaxation would be expected to lead to decreased diffusion, without any absorption of fresh fluid attributable to the action of a pump, and would thus result in an overall decrease in the rate of penetration of substances into cartilage.

Diffusion coefficients of carbon dioxide and glucose for a connective tissue membrane from individuals of various ages.

Diffusion coefficients of carbon dioxide and glucose for a connective tissue membrane from individuals of various ages.