Rates of glucose oxidation with a column reactor utilizing a magnetic field

Rates of glucose oxidation were measured with the use of a fluidized-bed column placed in a magnetic field and magnetite-containing beads of immobilized glucose oxidase and catalase. Its performance was predicted from the volumetric coefficient for liquid-phase mass transfer and the kinetic constants for glucose oxidation. Effusion of beads was negligible under the operating conditions employed.     

Antibiotics production in a fluidized bed reactor utilizing a transverse magnetic field

A mathematical model is developed to describe the performance of a three-phase fluidized bed reactor utilizing a transverse magnetic field. The model is based on the axially dispersed plug flow model for the bulk of liquid phase and on the Michaelis-Menten kinetics. The model equations are solved by the explicit finite difference method from transient to steady state conditions. The results of the numerical simulation indicate that the magnetic field increases the degree of bioconversion. The mathematical model is experimentally verified in a three-phase fluidized bed reactor with Penicillium chrysogenum immobilized on magnetic beads. The experimental results are well described by the developed model when the reactor operates in the stabilized regime. At low and relatively high magnetic field intensities certain discrepancy in the model solution is observed when the model over estimates the product concentration.     

Performance of fluidized-bed reactors utilizing magnetic fields

The performance of fluidized-bed reactors utilizing a magnetic field was determined by the use of magnetite-containing beads of immobilized unease. The reactors showed similar or higher conversions in comparison with fixed-bed reactors, although some aggregation of the beads in the magnetic field was observed. No effusion of the beads occurred up to a flow rate of 24 cm/min.     

Activity of an enzyme immobilized on superparamagnetic particles in a rotational magnetic field

We immobilize α-amylase extracted from Bacillus Iicheniformis on the surfaces of superparamagnetic particles and investigate the effect of a rotational magnetic field on the enzyme’s activity. We find that the activity of the enzyme molecules immobilized on superparamagnetic particles increases in the rotational magnetic field and reaches maximum at a certain frequency. We clarify the effect of the cluster structures formed by the superparamagnetic particles on the activity. Enzyme reactions are enhanced even in a tiny volume of solution using the present method, which is very important for the development of efficient micro reactors and micro total analysis systems (μ-TAS).     

Transient behavior of a continuous stirred tank biological reactor utilizing phenol as an inhibitory substrate

Transient experiments were conducted on a Pseudomomas utilizing phenol in a continuous culture by disturbing the influent substrate concentration and dilution rate. Two stable steady states existed for some ranges of the parameters. Highly damped oscillations were observed in approaching a new high conversion steady state or in returning to a new high conversion steady state following a small disturbance. When a large disturbance was applied there was a smooth (overdamped) approach to a new low conversion steady state. The observed oscillatory behavior for small disturbances was predicted by a modified Powell-Ierusalemskii bottleneck model, but could not be predicted by a Monod-Haldane model; neither model was accurate for predicting the effect of large disturbances. A constant wall growth factor was used to account for microbial film activity, and the existence of two stable states was directly due to the presence of the film.     

A simple preparation of an enzyme reactor producing nicotinamidemononucleotide

Summary An enzyme reactor which produces nicotinamidemononucleotide is easily prepared by adsorption of NAD pyrophosphatase to phosphocellulose. The separation and purification of the mononucleotide is achieved in a single chromatographic step. The spectrophotometric data of purified NMN and its cyanide adduct were redetermined.     

Kinetic study of a hollow-fiber enzyme reactor

Enzymes, such as urease and uricase, were entrapped in three kinds of hollow fibers. The apparent Michaelis–Menten constants K_m(app) obtained for these enzyme reactors were always larger than K_m of free enzyme because of the permeation resistance of substrate across the hollow-fiber membrane. K_m(app) increased with increasing degree of permeation resistance across the membrane by the increase in enzyme concentration. The half-life of the entrapped urease in the continuous reaction system was 60–80% of that of free enzyme. Activation energies of hollow-fiber enzyme reactors were always smaller than that of the free enzyme, because the activation energy of permeation was smaller than that of the enzyme reaction.     

Study of performance of a tubular membrane reactor for an enzyme catalyzed reaction

A tubular membrane reactor offers many advantages over a solid wall reactor to carry out an enzyme catalyzed reaction. With proper membrane selectivity, the product, may be separated from the reacting stream and the enzyme recycled for continuous reuse. In most cases, enzyme reuse contributes to the economic feasibility of a continuous enzyme catalyzed process. Furthermore, the efficiency and performance of a membrane reactor is greater than that of a solid wall reactor. Continuous hydrolysis of starch by the enzyme β-amylase, carried out in a commercially available tubular membrane unit, is studied at different starch and enzyme concentrations for a given system pressure and inlet flow rate. Results show that the performance of the membrane reactor is in all cases greater than that of the solid wall reactor. A steady state in performance of permeation rate is, however, not reached by the membrane reactor, which shows a continuous decline within the periods examined in this study. This decline is caused in part by the aging of the starch solution, but mostly by the formation of a concentrated, or gel, layer at the membrane surface. This appears to be the main limiting factor for this process since the decline in reaction and permeation rate results in a severe decrease in the amount of maltose in the permeate.     

Use of an enzyme thermistor in continuous measurements and enzyme reactor control.

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We decribe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containing immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.     

Kinetic study of a membrane enzyme reactor

A flat-membrane dialyzer was used as enzyme reactor by introducing enzyme solution into one of the membrane-separated chambers. The apparent Michaelis constant K_m(app) of urease was always larger (ten times at [urease] = 1 mg/ml) than that of free enzyme because the permeation of substrate through the membrane was rate determining. K_m(app) for urease decreased from 125 to 20mM with increasing flow rate of the substrate solution because of the turbulent flow near the membrane. In the case of glucose oxidase or creatine kinase, the reaction rate was limited by the permeation of less permeable substrates such as oxygen or ATP. Therefore, K_m(app) of more permeable substrates such as glucose or creatine became smaller than that of free enzyme. The reaction amount calculated from the permeation data agreed well with experimental results. By designing spacers for the reactor to give turbulence to the solution, the effectiveness of the reactor was improved fivefold.     

Ceramic membrane microfilter as an immobilized enzyme reactor.

This study investigated the use of a ceramic microfilter as an immobilized enzyme reactor. In this type of reactor, the substrate solution permeates the ceramic membrane and reacts with an enzyme that has been immobilized within its porous interior. The objective of this study was to examine the effect of permeation rate on the observed kinetic parameters for the immobilized enzyme in order to assess possible mass transfer influences or shear effects. Kinetic parameters were found to be independent of flow rate for immobilized penicillinase and lactate dehydrogenase. Therefore, neither mass transfer nor shear effects were observed for enzymes immobilized within the ceramic membrane. Both the residence time and the conversion in the microfilter reactor could be controlled simply by regulating the transmembrane pressure drop. This study suggests that a ceramic microfilter reactor can be a desirable alternative to a packed bed of porous particles, especially when an immobilized enzyme has high activity and a low Michaelis constant.     

Performance and characteristics of an anaerobic baffled reactor

The performance and the characteristics of a laboratory scale anaerobic baffled reactor (ABR) were investigated using synthetic wastewater. The experimental results showed that among different volatile fatty acids (VFAs), acetate was the main intermediate of acidogenic degradation of glucose. The VFA concentration decreased longitudinally down the reactor. The analysis of the biogas composition revealed that methane concentration increased steadily from compartment 1 to 5, while hydrogen content decreased in the first compartments. There was no detectable hydrogen in the last two compartments. The methane-producing activity of anaerobic sludge in different compartments depended on the substrate, which suggests that the proper anaerobic consortium in each separate compartment was developed according to the substrate(s) availability and the specific environmental conditions. The ABR has the potential to provide a higher efficiency at higher loading rates and be applicable for extreme environmental conditions and inhibitory compounds.     

Stability of chromatophores during ATP regeneration in an enzyme reactor

ATP regeneration from ADP and inorganic phosphate catalysed by chromatophores from Rhodo-spirillum rubrum has been coupled to the production of glucose-6-phosphate from glucose catalysed by hexokinase. Different ADP derivatives were tested in respect of their function as substrates for the chromatophores, but only 3′NH₂-ADP was phosphorylated. Several factors causing inactivation of the chromatophores during operational conditions were studied. The addition of radical scavengers resulted in an increased stability of the chromatophores, and it was concluded that free radicals had been formed in the presence of oxygen and caused damage to the membranes. In the presence of catalase, a stable ATP production was obtained for 6 h at an activity of 4.5 mol ATP × (mol bacteriochlorophyll)⁻¹ min⁻¹. In a nitrogen flushed reaction medium, the optimum concentration of the redox buffering ascorbic acid changed during the course of several hours of illumination, while it did not change in an air atmosphere.     

Production of penicillins and cephalosporins in an immobilized enzyme reactor

Summary Four enzymes required for the biosynthesis of pencillins and cephalosporins by Streptomyces clavuligerus have been immobilized on an anion exchange resin. The capabilities of the system have been studied by circulation of reaction mixtures through the immobilized enzyme reactor. Within 30 min, all of the substrate -(l--aminoadipyl)-l-cysteinyl-d-valine is consumed and converted to a mixture of penicillins and cephalosporins. After 60 min the major antibiotic products are (iso)penicillin N and desacetylcephalosporin C. The activity of the immobilized enzyme reactor activity is stable to storage at temperatures below 4°C but activity is lost on repeated use.     

Enantioselective esterification of butanol-2 in an enzyme membrane reactor

The enzymatic esterification of octanoic acid with racemic butanol-2 was investigated. Esterifications of the acid were performed in a forced flow enzyme membrane reactor. The used membrane was prepared by a phase inversion process in polyamide-6 solution followed by the chemical immobilization of a lipase-catalyst. Influences of water content and pH were estimated. Their optimum values are equal to 0.5% w/w and pH 8. The reaction rate (at 303 K) of 5.1 × 10^?5 mol/h·cm² of the membrane area, and at least 85% enantiomeric excess in the produced ester mixture were obtained. The activity of immobilized lipase in the membrane process is about two times higher than that of the native lipase in the esterification performed in a tank reactor.     

Characterization of a perfusion reactor utilizing mammalian cells on microcarrier beads

Our overall objective is to develop a cell culture analogue bioreactor (CCA) that can be used together with a corresponding physiologically based pharmacokinetic model (PBPK) to evaluate molecular mechanisms of toxicity. The PBPK is a mathematical model that divides the body into compartments representing organs, integrating the kinetic, thermodynamic, and anatomical parameters of the animal. The CCA bioreactor is a physical replica of the PBPK; where the PBPK specifies organs, the CCA bioreactor contains compartments with a corresponding cell type that mimics some of the characteristic metabolism of that organ. The device is a continuous, dynamic system composed of multiple cell types that interact through a common circulating cell culture medium. The CCA bioreactor and the model can be coupled to evaluate the plausibility of the molecular mechanism that is input into the model. This paper focuses on the design, development, and characterization of a CCA bioreactor to be used in naphthalene dose response studies. A CCA bioreactor prototype developed previously is improved upon by culturing the cells on microcarrier beads. Microcarrier beads with cells attached can form packed beds with cell culture medium perfusing the beds. In this study, two packed beds of cells, one with L2 cells (rat lung) and one with H4IIE cells (rat hepatoma), are linked in a physiologically relevant arrangement by a common recirculating cell culture medium. Studies of this CCA bioreactor presented here include mixing profiles, effect of reactor environment on cell viability and intracellular glutathione, naphthalene distribution profile, and initial naphthalene dosing studies. Unlike the prototype system there is no detectable response to naphthalene addition; in a companion paper we show that this discrepancy can be explained by differences in liquid residence times in the organ compartments. The perfusion reactor design is shown to have significant operating improvements over prototype designs.     

Modelling as a tool of enzyme reaction engineering for enzyme reactor development

Strategy of the development of model for enzyme reactor at laboratory scale with respect to the modelling of kinetics is presented. The recent literature on the mathematic modelling on enzyme reaction rate is emphasized.     

Effect of an external RF field on the beam-plasma discharge in a magnetic field

The effect of an RF field on a steady-state beam-plasma discharge with a plane electrode placed parallel to a sheetlike electron beam is studied experimentally. The plasma parameters were measured by a single probe, and the electron distribution function was determined with the use of an electrostatic analyzer. The energy and current of the electron beam were E _B=2.5 keV and J _B=0.05–1.5 A, respectively. The working pressure was p=2×10^?5–10^?3 torr. The frequency of the external RF field was 13.56 MHz. Both the steady-state regimes in which the RF field had no effect on the plasma parameters and regimes with a pronounced effect of the RF field were observed. The experiments show that the regime of the discharge depends strongly on the plasma density and the magnetic field. The parametric instability is studied theoretically in the weak-turbulence approximation. It is shown that, due to the decay nature of the spectrum of plasma oscillations, the onset of instability is accompanied by the transfer of the energy of fluctuations over the spectrum, from the pump frequency toward its harmonics.     

Maltodextrin hydrolysis in a fluidized-bed immobilized enzyme reactor

The present work deals with maltodextrin hydrolysis by glucoamylase immobilized onto corn stover in a fluidized bed reactor. An industrial enzyme preparation was covalently grafted onto corn stover, yielding an activity of up to 372 U/g and 1700 U/g for support particle sizes of 0.8 and 0.2 mm, respectively. A detailed kinetic study, using a differential reactor, allowed the characterization of the influence of mass transfer resistance on the reaction catalyzed by immobilized glucoamylase. A simple and general mathematical model was then developed to describe the experimental conversion data and found to be valid.     

Nonisothermal immobilized enzyme reaction in a packed-bed reactor

Summary This work investigates the reaction behavior of immobilized enzymes in a packed-bed reactor. The effect of heat generation due to exothermic enzyme reaction is considered. Conservations of substrate and energy constitute two coupled nonlinear partial differential equations which are simultaneously solved by a numerical method. It is found that substrate conversion is generally increased at higher temperature. However, the extent of temperature heavily depends on the magnitude of the dimensionless Michaelis constant which is defined as the ratio of Michaelis constant to inlet substrate concentration. At low dimensionless Michaelis constant, substrate conversion is considerably affected by temperature, but at high dimensionless Michaelis constant, the temperature effect is negligibly small. It is also found that maximum bulk temperature of reaction mixtures occurs around a dimensionless reactor length of 1.3 for the case with high substrate conversion.