Showing papers in "Biotechnology and Bioengineering in 1989"
TL;DR: Beads with the highest mechanical strength, lowest shrinkage, best stability towards monovalent cations, and highest porosity were made from alginate with a content of L‐guluronic acid higher than 70% and an average length of the G‐blocks higher than 15.4 × 105.
Abstract: Calcium alginate gel beads were prepared from a range of well characterized alginates. The physical properties of beads depended strongly on the composition, sequential structure, and molecular size of the polymers. Beads with the highest mechanical strength, lowest shrinkage, best stability towards monovalent cations, and highest porosity were made from alginate with a content of L-guluronic acid higher than 70% and an average length of the G-blocks higher than 15. For these "high G" alginates the critical overlap intrinsic viscosities have been determined, and for molecular weight higher than 2.4 x 10(5), the gel strength was independent of the molecular weight.
902 citations
TL;DR: The main objective of the present investigation was the screening and selection of the most potent marine algal type for sequestering of cobalt and the biosorption process based on this biomass may represent a possible alternative to the conventional cobalt recovery processes.
Abstract: The main objective of the present investigation was the screening and selection of the most potent marine algal type for sequestering of cobalt. The biosorption process based on this biomass may represent a possible alternative to the conventional cobalt recovery processes
248 citations
TL;DR: The economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated and reverse osmosis was found to be economically feasible for preconcentration to about 5–10 wt % depending on the concentration of the feed.
Abstract: The economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated. Two methods, evaporation and reverse osmosis, are compared. A computer program to determine the optimal preconcentration conditions for glucose solutions of 1.5–16 wt% has been developed. It was used to compute the fractional cost for labor and maintenance, preconcentration, fermentation, and distillation. Preconcentration with evaporation resulted in a higher total cost, compared with no preconcentration, for all cases studied, although a six-effect unit was used. Reverse osmosis was found to be economically feasible for preconcentration to about 5–10 wt % depending on the concentration of the feed.
200 citations
TL;DR: Theories of protein partitioning in two-phase polymer systems which account for the effects of different aspects of system composition are reviewed in this article, where some recommendations for future work are given.
Abstract: Theories of protein partitioning in two-phase polymer systems which account for the effects of different aspects of system composition—such as the choice of materials, protein size, polymer molecular weight, polymer concentration, salt concentration, and affinity ligands—are reviewed. Although the present models provide some information about specific aspects of partitioning, a comprehensive and fundamental theory which can be used to predict protein partitioning behavior has not yet been developed. Some recommendations for future work are given.
199 citations
TL;DR: Nonliving biomass of the common seaweed Ascophyllum nodosum is capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co2+/g, revealing that the metal uptake phenomenon is reversible, implying physical sorption of cobalt.
Abstract: Nonliving biomass of the common seaweed Ascophyllum nodosum is capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co(2+)/g. Successful desorption of cobalt from the biomass by acidic CaCl(2) solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of cobalt. Chemical and instrumental analysis including electron microscopy, infrared (IR) spectroscopy, X-ray dispersion and diffraction analysis provided supporting evidence that the biosorption mechanism involves predominantly ion exchange. Alginates of the cell wall (-COOH groups) play an important role in cobalt binding. Coordination and sorption in the cell wall structure occur simultaneously and rapidly whereas penetration of cobalt into the cell occurs at a lower rate.
193 citations
TL;DR: The stabilities of the enzyme vs. pH and heat were much improved by the immobilization with silk, and the activity was maintained to the higher values on both sides of the optimum pH compared with the case of free enzymes.
Abstract: Glucose oxidase (GOD) was immobilized in Bombyx mori silk fibroin membrane by only physical treatment, i.e., stretching without any chemical reagents. This is due to the structural transition of the silk fibroin membrane from random coil to antiparallel beta-sheet (Silk II) induced by the stretching treatment. Permeability coefficients of glucose and oxygen through the fibroin membrane were determined; the permeability of glucose decreased with increasing degree of stretching. The immobilized enzyme activity was characterized with apparent Michaelis constant K(m) (app) and maximal activity V(m). Optimum pH of the activity of the immobilized enzyme was shifted to the value around neutrality, and the activity was maintained to the higher values on both sides of the optimum pH compared with the case of free enzymes. Thermal stability was scarcely lost even at 50 degrees C, although the free enzyme lost about 70% of the original activity. Thus, the stabilities of the enzyme vs. pH and heat were much improved by the immobilization with silk. Glucose sensor prepared with this GOD-immobilized fibroin membrane was developed; the capabilities such as the response time, calibration curve, and repeating usage were determined.
159 citations
TL;DR: This work reports on the development of a quantitative model that addresses the basic mechanisms inherent in many uptake processes in algae and bacteria, and postulates two mechanisms: an initial rapid metal ion uptake due to attachment onto the cell wall followed by a relatively slow uptakeDue to membrane transport of the metal into the cell.
Abstract: The ability of algae and bacteria to accumulate heavy metals from the surrounding environment is a widely recognized phenomenon that has a number of important implications. This work reports on the development of a quantitative model that addresses the basic mechanisms inherent in many uptake processes. The model postulates two mechanisms: an initial rapid metal ion uptake due to attachment onto the cell wall followed by a relatively slow uptake due to membrane transport of the metal into the cell. The mathematical model has been tested using the alga Chlorella vulgaris in the presence of cadmium and zinc in solution under various experimental conditions.
157 citations
TL;DR: A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by‐product yields from glutamine, preceded the increase in cell concentration after the glucose step change.
Abstract: Glucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady-state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100-200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by-product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day(-1). The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.
157 citations
TL;DR: The methodology for predicting dipeptide partition coefficients was extended to proteins, where it was found that low‐molecular‐weight proteins gave a linear relationship with the tie line compositions of a phase diagram.
Abstract: Phase diagram data at 4 degrees C was determined for the aqueous two-phase systems composed of polyethylene glycol, dextran, and water. The Flory-Huggins theory of polymer thermodynamics was used to correlate partitioning of biomolecules in these aqueous two-phase systems resulting in a simple linear relationship between the natural logarithm of the partition coefficient and the concentration of polymers in the two phases. This relationship was verified by partitioning a series of dipeptides which differ from one another by the addition of a CH(2) group on the c-terminal amino acid residue and by utilizing a set of low-molecular-weight proteins. The slope of the line could be expressed in terms of the interactions of the biomolecule with the phase forming polymers and water. The main result for the dipeptides was that knowledge of the partition coefficient in any of the PEG/dextran/water systems, regardless of polymer molecular weight, enabled prediction of the coefficient in all of the systems. The dipeptides were also used for determination of the Gibbs free energy of transfer of a CH(2) group between the phases. This quantity was correlated with polymer concentration, thus establishing a hydrophobicity profile for the PEG/ dextran/water systems. The methodology for predicting dipeptide partition coefficients was extended to proteins, where it was found that low-molecular-weight proteins gave a linear relationship with the tie line compositions of a phase diagram.
147 citations
TL;DR: New experimental results are presented which illustrate the protective effect of thickening agents in turbulent fluid flow fields and follow the prediction of a model based on Kolmogorov's theory of universal equilibrium in turbulent flow fields.
Abstract: Animal cells are exposed to turbulent fluid flow in many cell culture processes. If the turbulence in the flow is sufficiently strong, the cells will be damaged or killed by fluid-mechanical forces. Through an increase in viscosity, the turbulence can be damped and the hydro-dynamic damage can be reduced. In this article, new experimental results are presented which illustrate the protective effect of thickening agents. The results follow the prediction of a model based on Kolmogorov's theory of universal equilibrium in turbulent flow fields.
140 citations
TL;DR: Explosive depressurization appears to be the preferred method and has the added benefit of altering the chemical structure of the wood to enhance the enzymatic hydrolysis of the cellulose fraction.
Abstract: The energy requirements associated with conventional mechanical size reduction of poplar and aspen wood are compared to a new method of size reduction employing a wood planer. Although the planer requires about 2.3 times less energy to achieve the same size reduction as conventional methods, large-scale equipment to implement this approach does not currently exist. Explosive depressurization was also compared to conventional mechanical size reduction. The conventional mechanical methods require roughly 70% more energy to achieve the same size reduction as explosive depressurization. Thus, explosive depressurization appears to be the preferred method and has the added benefit of altering the chemical structure of the wood to enhance the enzymatic hydrolysis of the cellulose fraction.
TL;DR: This communication describes a method for the production of high levels of rhamnolipid from Pseudomonas aeruginosa in a defined culture medium containing corn oil, which is easily separated and hydrolyzed to produce a mixture ofrhamnose and a fatty acid, 3-hydroxydecanoic acid.
Abstract: This communication describes a method for the production of high levels of rhamnolipid from Pseudomonas aeruginosa in a defined culture medium containing corn oil. The isolated rhamnolipid is then hydrolyzed to produce a mixture of rhamnose and a fatty acid, 3-hydroxydecanoic acid, which are easily separated
TL;DR: The main factors responsible for the decline in performance during the harvesting of B. polymyxa broth by membrane microfiltration are determined and a new mass transport model—the solids flux model—based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid–solution interface attach (stick) completely are tested.
Abstract: Although cross-flow membrane filtration is a very attractive option for harvesting cells and recovering enzymes from cell homogenates, the process is not without its problems. Foremost of these is the deposit of dissolved and suspended solutes onto the membrane surface during operation. The formation of these dense and sometimes compressive sublayers (often called cakes) offers additional resistance to axial and permeate flows and often affects the retention characteristics of the process. In view of the complex nature of the sublayer formation process and its sensitivity to cross-flow velocity, this investigation was undertaken to determine the main factors responsible for the decline in performance during the harvesting of B. polymyxa broth by membrane microfiltration. System parameters varied include axial flow rate, concentration of cells, proteins and other components in the feed, membrane materials (ceramic, polypropylene, and stainless steel), and cleaning methods. To help explain the observed results, a new mass transport model-the solids flux model-based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid-solution interface attach (stick) completely, is tested. Using a variety of diagnostic methods, magnesium ammonium phosphate precipitate is formed during steam sterilization of the medium and is implicated as the major foulant in this study.
TL;DR: In this article, power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied under unaerated and aerated conditions.
Abstract: Aerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height-to-diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding-loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed-filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller-impeller flow pattern interactions occur.
TL;DR: This communication points out some significant disparities in the available shear rate data and discusses the errors in the publicly available methods of estimating theShear rate.
Abstract: Continuing developments in biotechnology have made available several new biocatalysts ― hybridomas, plant cells, and genetically engineered microorganisms ― for use in production. Many of these catalytic entities have been demonstrated to be sensitive to shear. In this context, the question of prevailing shear rate, particularly in low-shear bubble column and airlift bioreactors, deserves attention. This communication points out some significant disparities in the available shear rate data and discusses the errors in the available methods of estimating the shear rate
TL;DR: The advantages and limitations of using membrane bioreactors for entrapping whole cells and enzymes, including single, laminated and microporous, for the conversion of optically active enantiomers are reviewed.
Abstract: Integrating the properties of synthetic membranes with biological catalysts such as cells and enzymes forms the basis of an exciting new technology called membrane bioreactors. The impetus behind this marriage comes from the recent spectacular advances in recombinant DMA and cell fusion technologies and the need to develop competitive bioprocessing schemes to produce complex and active biological molecules. The advantages and limitations of using membrane bioreactors for entrapping whole cells and enzymes are reviewed. Various membrane configurations such as microcapsules, hollow fibers, and flat sheets are compared. Several different entrapped membrane bioreactors, including single, laminated and microporous, for the conversion of optically active enantiomers are described. As with new and exciting technologies, the future of membrane bioreactors in biotechnology will depend on their ability to produce desired molecules at competitive costs.
TL;DR: Un certain nombre de proteines standards, ayant des proprietes physicochimiques connues, tels la BSA, le cytochrome C, the γ globuline, le lysozyme, l'ovalbumine, the myoglobine..., sont utilisees pour etudier le comportement de proteine dans un systeme triphasique de partage.
Abstract: Un certain nombre de proteines standards, ayant des proprietes physicochimiques connues, tels la BSA, le cytochrome C, la γ globuline, le lysozyme, l'ovalbumine, la myoglobine..., sont utilisees pour etudier le comportement de proteine dans un systeme triphasique de partage. Les effets de differents facteurs: pH, pI, temperature, concentration, masse moleculaire, ... intervenants dans la distribution de la proteine dans le systeme triphasique, sont etudies. Pour valider cette technique, une experience temoin utilisant les memes proteines standards est effectuee en electrophorese SDS-PAGE
TL;DR: Calculations for the fed‐batch penicillin fermentation indicate sharp increases in productivity over frequently employed strategies.
Abstract: The determination of the optimal feeding profile of a fed-batch fermentation requires the solution of a singular optimal control problem that is often complicated by constraints imposed on the state variables. Such constraints can be a maximum allowable biomass concentration beyond which oxygen transfer is severely limited or maximum substrate concentration to avoid side reactions. Due to these state constraints and the singular nature of the problem, complete solutions are especially hard to obtain and almost nonexistent in the literature. In this work the feed concentration is employed as the control variable in a solution approach that first determines the optimal reactor substrate concentration and subsequently solves for the feed concentration profile that results in the optimal reactor profile. Calculations for the fed-batch penicillin fermentation indicate sharp increases in productivity over frequently employed strategies.
TL;DR: The model represents the first to include any degree of metabolic detail and structure in describing a hybridoma culture and can be a useful tool to study various strategies for enhancing hybridoma growth as well as viability and the production of monoclonal antibodies in suspension cultures.
Abstract: A structured kinetic model is developed to describe the dynamics of hybridoma growth and the production of monoclonal antibodies and metabolic waste products in suspension culture. The crucial details of known metabolic processes in hybridoma cells are incorporated by dividing the cell mass into four intracellular metabolic pools. The model framework and structure allow the dynamic calculation of the instantaneous specific growth rate of a hybridoma culture. The steady state and dynamic simulations of the model equations exhibit excellent agreement with experimentally observed trends in substrate utilization and product formation. The model represents the first to include any degree of metabolic detail and structure in describing a hybridoma culture. In so doing, it provides the basic modeling framework for incorporating further details of metabolism and can be a useful tool to study various strategies for enhancing hybridoma growth as well as viability and the production of monoclonal antibodies in suspension cultures.
TL;DR: An algorithm for operating a fed‐batch fermentor at an optimum specific fermentation rate is proposed that does not require on‐line measurement of nutrient concentration in the culture medium and works well even with poor estimates of the product yields and the Specific fermentation rate.
Abstract: An algorithm for operating a fed-batch fermentor at an optimum specific fermentation rate is proposed. It does not require on-line measurement of nutrient concentration in the culture medium. An on-line estimate of the specific fermentation rate is sufficient for implementation of this scheme. The algorithm is model independent and works well even with poor estimates of the product yields and the specific fermentation rate. Results of a detailed simulation study are presented for a simple case of optimization of cell-mass production in a fed-batch fermentor. The results clearly demonstrate the efficacy of this algorithm under a wide range of fermentation situations.
TL;DR: The oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans and it was found that under atmospheric conditions, and at Fe2- < 0.001M, T < 25°C, andAt pH above 2.2, the oxidation rate is independent of H+ Concentration.
Abstract: The oxidation of Fe(2+) with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe(2+) < 0.001M, T < 25 degrees C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression: -(d[Fe(2+)]) / dt = 1.62 x 10(11)C(bact) [H(+)] [Fe(2+)] p O(2)e(-(58.77/RT)). Below pH = 2.2, the oxidation rate is independent of H(+) Concentration.
TL;DR: It was found that the formation of glucose can be described by summation of two parallel first order reactions and the extent of hydrolysis at fixed time increases with increasing enzyme dosage in a hyperbolic function.
Abstract: The relationship among extent of hydrolysis, reaction time, and enzyme dosage was investigated. For this, Sigmacell 50 and pretreated poplar wood (20 g/L) was hydrolyzed with varying dosages of cellulases from three different sources (5 to 100 FPU/g) for time periods ranging from 2 to 94 h. It was found that the formation of glucose can be described by summation of two parallel first order reactions. The extent of hydrolysis at fixed time increases with increasing enzyme dosage in a hyperbolic function. From the empirical data it is possible to calculate the fractions of easily and difficult hydrolyzable cellulose and the digestability which could maximally be obtained at infinite enzyme loadings. In the system Sigmacell 50 and Celluclast the easily and difficult hydrolyzable components are 43.0 and 57.0%, respectively, and the maximum digestability at 94 h is 82.6%. Poplar wood, steam treated at 200 degrees , 220 degrees , and 240 degrees C, showed with Celluclast at 24 h a maximum digestability (weight percentage of wood degraded to glucose) of 43.9, 64.9, and 68.0%. The relationships derived from experimental data allow one to compare objectively the effectiveness of different cellulase enzymes and different pretreatments.
TL;DR: DNA measurements indicated that the reduction in net growth was due entirely to cell death, from hydrodynamic forces, from hydrostatic forces, for animal cells growing on microcarriers.
Abstract: The effects of hydrodynamic forces on cell growth are investigated for animal cells growing on microcarriers. A reduction in net growth was observed with high levels of agitation. DNA measurements indicated that the reduction in net growth was due entirely to cell death, from hydrodynamic forces. No inhibition or enhancement of cell replication appeared to occur with high levels of agitation.
TL;DR: A “physiological state control approach” has been developed using the concept of representing fermentation processes through the current physiological state of the cell culture using a conventional mathematical model.
Abstract: In this article a novel approach to the control of fermentation processes is introduced. A "physiological state control approach" has been developed using the concept of representing fermentation processes through the current physiological state of the cell culture. No conventional mathematical model is required for the synthesis of such a control system.The main idea is based on the fact that during batch, feed-batch, or even continuous cultivation the physiological characteristics of the cell population, jointly expressed by the term "physiological state", are not constant but rather variable, which is reflected in expected or unexpected changes in the behavior of the control plant, and which requires flexible alteration of the current control strategy. The proposed approach involves decomposition of the physiological state space into several subspaces called "physiological situations." In every physiological situation the cell population expresses stable characteristics, and therefore an invariant control strategy can be effectively applied. The on-line functions of the physiological state control system consist of the calculation of physiological state variables, determination of the current physiological situation as an element of a previously defined set of known physiological situations, switching of the relevant control strategy, and calculation of the control action. Attention is focused on the synthesis of the novel and nonstandard part of the control system - the algorithm for online recognition of the current physiological state. To this end an effective approach, based on artificial intelligence methods, particularly fuzzy sets theory and pattern recognition theory, was developed. Its practical realization is demonstrated using data from a continuous fermentation process for single cell protein production.
TL;DR: Thorium uptake was increased by pretreatment using detergent and also, in the case of filamentous fungi, varied with the culture conditions, which implies that the thorium uptake characteristics of fungal biomass are able to be manipulated by these or similar means for optimum performance.
Abstract: Biomass from several fungal species removed thorium from solution in 1M HNO(3), pH 0-1. Thorium uptake was saturable with increasing thorium concentration, although the equilibria did not correspond to a simple ad sorption isotherm. Thorium uptake was altered by the biomass concentration, the uptake per unit biomass being reduced at high biomass concentrations. The presence of Al(3+) and Fe(3+) only slightly inhibited uptake of thorium while Ca(2+), Mg(2+), and Na(+) had no effect. Thus fungal biomass appears capable of removing thorium from solution under chemical conditions existing in acid waste liquors. Thorium uptake was increased by pretreatment using detergent and also, in the case of filamentous fungi, varied with the culture conditions, which implies that the thorium uptake characteristics of fungal biomass are able to be manipulated by these or similar means for optimum performance.
TL;DR: The stability of the bound lipase was extremely good, no loss in activity being observed after a period of three weeks in aqueous solution of 37°C, and values considerably higher than previously reported in the literature for covalently immobilized lipase.
Abstract: Lipase from Rhizopus sp. has been immobilized covalently on tresyl activated silica. Three different coupling media were evaluated: aqueous buffer, n-hexane, and a microemulsion based on n-hexane, aqueous buffer, and the nonionic surfactant triethylene glycol monododecyl ether. In addition, coupling via a very long, hydrophilic spacer arm, polyethylene glycol 1500 (PEG 1500), was compared with attachment to the silica via a short silane bridge only. The enzyme preparations were tested in hydrolysis and transesterification reactions. In the hydrolysis no marked differences in activity were found between the coupling media used. In the transesterification, on the other hand, the choice of immobilization medium had a very large effect on lipase activity, the preparation from microemulsion being the most active one. The use of the hydrophilic spacer had a large effect on activity in the hydrolysis reaction. Whereas direct coupling gave an activity of immobilized lipase of 26-34% of that of free enzyme, depending on the reaction medium, lipase bound via the spacer exhibited 56-67% activity. The latter values are considerably higher than previously reported in the literature for covalently immobilized lipase. The hydrophilic spacer had no effect on enzyme activity in the transesterification, however, a fact which is attributed to the hydrophobic medium of this reaction. The spacer is incompatible with the reaction medium and will, therefore, adsorb on the particles rather than stretch out into the bulk phase. The stability of the bound lipase was extremely good, no loss in activity being observed after a period of three weeks in aqueous solution of 37 degrees C.
TL;DR: The effect of Aw is reported on the catalytic performance of alcohol oxidase acting on ethanol vapors, postulated that during the gas‐phase reaction the ethanol on the enzyme establishes an equilibrium with the ethanol vapor similar to that between ethanol in water and ethanol in the gas phase.
Abstract: The enzymatic conversion of gaseous substrates represents a novel concept in bioprocessing. A critical parameter in such systems is the water activity, A(w) The present article reports the effect of A(w) on the catalytic performance of alcohol oxidase acting on ethanol vapors. Enzyme activity in the gas-phase reaction increases several orders of magnitude, whereas the thermostability decreases drastically when A(w) is increased from 0.11 to 0.97. The enzyme is active on gaseous substrates even at hydration levels below the monolayer coverage. Enhanced thermostability at lower hydrations results in an increase in the optimum temperature of the gas-phase reaction catalyzed by alcohol oxidase. The apparent activation energy decreases as A(w) increases, approaching the value obtained for the enzyme in aqueous solution. The formation of a pread-sorbed ethanol phase on the surface of the support is not a prerequisite for the reaction, suggesting that the reaction occurs by direct interaction of the gaseous substrate with the enzyme. The gas-phase reaction follows Michaelis-Menten kinetics, with a K(m) value almost 100 times lower than that in aqueous solution. Based on vapor-liquid equilibrium data and observed K(m) values, it is postulated that during the gas-phase reaction the ethanol on the enzyme establishes an equilibrium with the ethanol vapor similar to that between ethanol in water and ethanol in the gas phase.
TL;DR: Following an effective accumulation of cobalt by nonliving algal biomass of Ascophyllum nodosum, the desorption release of the metal from the biosorbent was examined using H2SO4, HCl, NH4OH, KHCO3, EDTA, KSCN, KCl, and CaCl2 solutions.
Abstract: Following an effective accumulation of cobalt by nonliving algal biomass of Ascophyllum nodosum, the desorption release of the metal from the biosorbent was examined using H(2)SO(4), HCl, NH(4)OH, KHCO(3), EDTA, KSCN, KCl, and CaCl(2) solutions. The solution of CaCl(2) (0.05M) in HCl appeared to be the best eluant capable of desorbing more than 96% of the sequestered cobalt at the optimum pH 2-3. The optimum solid-to-liquid ratio was more than 10 with the cobalt reuptake capacity of the biosorbent undiminished. The effect of temperature on the elution process and the elution rate was not significant up to 60 degrees C. The infrared (IR) spectra of the native and the eluted biomass did not show significant differences. The electron micrographs of the algal biomass taken after washing it with the CaCl(2) (0.1M) eluant solution indicated no damage to the cells and cell walls, while strong acid, alkaline, and KSCN treatment resulted in some changes in the cellular structure. The kinetics of the cobalt stripping process was quite rapid. The required contact time for the complete metal removal from the biomass was shorter than 2 h, even for the highest levels of cobalt initially deposited on the biomass.
TL;DR: A method for determining fermentation parameters of a gaseous substrate in convenient batch vessels using a modified Monod model is presented and experimental data for the conversion of carbon monoxide to acetate by the strict anaerobe Peptostreptococcus productus is illustrated.
Abstract: The fermentation of gaseous substrates such as CO, H2, and CO2 may be performed in a continuous stirred tank reactor, as well as the traditional batch reactor. In this article, the conversion of carbon monoxide by Peptostreptococcus productus is demonstrated in a stirred tank reactor under both mass transfer-controlled and nonmass transfer-controlled conditions. Utilizing a non-steady-state procedure, intrinsic rates are evaluated under non-mass transfer-controlled conditions in a time period of only 5–6 hours. A steady-state procedure was used to evaluate CSTR performance under mass transfer-controlled conditions. The mass transfer coefficient was calculated, followed by the development of a model to predict CSTR behavior for this gas phase substrate.
TL;DR: A dynamic method is proposed for kla measurement in aerated and agitated reactors, in which achange in the total pressure in the reactor by approximately 20% leads to a simultaneous change in the oxygen concentration in all the bubbles in the dispersion, suppresses the influence of nonideal mixing of the gas phase on the kla value.
Abstract: A dynamic method is proposed for kla measurement in aerated and agitated reactors, in which a change in the total pressure in the reactor by approximately 20% leads to a simultaneous change in the oxygen concentration in all the bubbles in the dispersion. This procedure suppresses the influence of nonideal mixing of the gas phase on the kla value. Other dynamic methods so far used do not possess this advantage. They are based on a step change in oxygen concentration in the entering gas, where the interfacial nitrogen transport and the finite rate of the concentration change propagation into the individual bubbles in the dispersion can cause an error in the reported kla values of more than hundreds of percent. The reliability of the pressure method is tested by comparison both with the standard dynamic method, in which pure oxygen is absorbed in a liquid from which all other gas components were previously removed, and with the steady-state sulphite method. The signal of the oxygen probe used in the experiments must be independent of the pressure. A test for this in dependence is described. The pressure method is also suitable for large-scale reactors since the necessary pressure changes are sufficiently small and, morever, air can be used.