bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of the siderophore enterobactin: Use of four different fermentation systems and identification of the compound by HPLC
Authors: Seiffert Andreas , Goeke Klaus , Fielder Hans‐Peter , Zähner Hans
Published: December 2004

The article describes four different fermentation procedures for Escherichia coli AN311, a producer of enterobactin. A regular rotary shaker culture with a biphasic system consisting of an agar layer (as a reservoir for feeding processes) and a layer of liquid medium, 2.4 L and 10 L batch cultures, and a novel dialysis membrane fermentor were used. With the use of this latter fermentor type, the production of enterobactin could be increased by a factor of about 9.5, while growth increased by a factor of 12 compared to the other systems. For the rapid and reliable quantification of the concentration and purity of enterobactin an analytical and preparative high‐performance liquid chromatography (HPLC) method was established. The degradation compounds of this siderophore were detected by diodearray and bioassays. A comparison of total catechol production as well as the distribution between enterobactin and its degradation compounds is given. © 1993 John Wiley & Sons, Inc.
Mass transport parameters of aspen wood chip beds via stimulus‐response tracer techniques
Authors: Hradil G. , Calo J. M. , Wunderlich T. K.
Published: December 2004

A stimulus–response tracer technique has been used to characterize packed beds of untreated, as well as acid prehydrolyzed, and enzymatically hydrolyzed aspen wood chips. Glucose was used as the tracer. Bulk liquid phase dispersion, interphase mass transfer, and intraparticle diffusion coefficients were determined for these materials as well as effective porosities and tortuosities. The untreated and prehydrolyzed aspen wood chips were found to have effective coid fractions of ca. 0.8, while the enzymatically hydrolyzed wood chips exhibited a void fraction of 0.37. Intraparticle diffusion was approximately twice as rapid in the prehydrolyzed and enzymatically hydrolyzed wood chips as in the untreated wood chips. Also, under the current experimental conditions, intraparticle diffusional transport resistance accounted for roughly half of the total tracer pulse dispersion. It is demonstrated that stimulus‐response tracer techniques can be useful and convenient probes for beds of lignocellulosic, or other conversion and/or treatment. © 1993 John Wiley & Sons, Inc.
Intrinsic fermentation kinetics of lactose in acidogenic biofilms
Authors: Yu Jian , Pinder Kenneth L.
Published: December 2004

The intrinsic fermentation kinetics of lactose in acidogenic biofilms were investigated in situ in a continuous flow fermentor at 35°C and pH 4.6. The external and internal mass transfer resistances to lactose molecules from bulk solution to inside the biofilms were experimentally minimized or eliminated in a thin biofilm and recycled medium. In a chemically defined culture medium, the immobilized acidogens converted lactose mainly to acetate and butyrate; the minor products included ethanol. propionate, lactate, and hydrogen. The utilization rate of lactose, as a function of lactose concentration in the fermentor, can be described by a Michaelis‐Menten equation, as can the formation rates of acetate, butyrate, and ethanol. The production rates of propionate and lactate had a liner relationship with lactose concentration under the experimental conditions. The low pH (4.6) of culture medium could depress the formation of propionate, and intermediate which is most difficulty digested by acetogenic bacteria located in the second fermentor in a two‐phase process. Production rate of acetate quickly reached a constant, and additional utilization of lactose produced more butyrate and other minor products. © 1993 John Wiley & Sons, Inc.
Comparison of three different promoter systems for secretory α‐amylase production in fed‐batch cultures of recombinant Saccharomyces cerevisiae
Authors: Park Yong Soo , Shiba Sumihisa , lijima Shinji , Kobayashi Takeshi , Hishinuma Fumio
Published: December 2004

Cloned gene expression in recombinant Saccharomyces cerevisiae 20B‐12 containing three different plasmids was compared in batch and fed‐batch cultures. The plasmids pNA3, pNA7, and pNA9 contain the α‐amylase gene under the control of SUC2, PGK, and GAL7 Promoters, respectively. The synthesis of α‐amylase was therefore induced by low glucose concentration for the SUC2 and PGK promoters, and by galactose for GAL7 promoter. The specific cell growth rates were similar among cells harboring the three different plasmids; they decreased from 0.35 to 0.38 h−1 during the cell growth phase to 0.03 to 0.06h−1 during the production phase. The secretory α‐amylase activity of cells harboring plasmid pNA7 was 129 U/mL in fed‐batch culture, which was 1.4 and 2 times as high as the activities of cells harboring plasmids pNA3 and pNA9, respectively. The secretion ratios (amount of extracellular α‐amylase activity/amounts of total α‐amylase activity) of cells harboring plasmids pNA3, pNA7, and pNA9 were 91.4%, 94.5%, and 95.3%, respectively. © 1993 Wiley & Sons, Inc.
Homogeneous immunoassay of polyclonal antibodies by use of antigen‐coupled liposomes
Authors: Katoh Shigeo , Sohma Yoshinori , Mori Yoshikazu , Fujita Ryoji , Sada Eizo , Kishimura Masaaki , Fukuda Hideki
Published: December 2004

Anti‐cytochrome c and anti‐myoglobin antibodies were assayed by use of immunoliposomes coupled with the antigens. Addition of complement under the existence of the antigens. Addition of complement under the existence of the antigen‐antibody complex on the surface of the liposome caused lysis of the liposomes, which was proportional to the amount of the antigen‐antibody complex formed as well as the concentration of complement added. Thus, the degree of marker release depended on the average association constant and also on its heterogeneity of the polyclonal antibodies, which shows that the results assayed by this method are correlated to the antibody ability to form the antigen‐antibody complex © 1993 Wiley & Sons, Inc.
Affinity precipitation of proteins by polyligands
Authors: Morris John E. , Hoffman Allan S. , Fisher Rod R.
Published: December 2004

A novel technique for affinity precipitation has been developed in which multimeric target proteins are precipitated as a result of network formation by polymer‐conjugated ligands (polyligands). A polyligand precipitant for avidin was synthesized by conjugation of biotin to a polyacrylamide‐based backbone. The effects of mixing conditions, ligand substitution frequency, and molecular weight on affinity precipitation were examined using the biotin‐PAAm precipitant. Biotin was replaced by iminobiotin to study the effect of the ligand‐protein dissociation constant o affinity precipitation. The iminobiotin‐PAAm precipitant was also used to examine the reversibility of the precipitation and recovery of the target protein after precipitation. © 1993 Wiley & Sons, Inc.
Dimensionless criteria for estimating oxygen transfer in aeration systems
Authors: Ognean T.
Published: December 2004

The effect of power consumption on oxygen transfer efficiency has been evaluated for both surface and subsurface aeration systems. Two new dimensionless criteria (numbers) have been proposed for this purpose. They are termed the efficiency criterion or To number and the power consumption effect criterion or Av number. The analysis presented in this article is based on data obtained on various full‐scale aeration systems, and it shows that for each aerator there is an optimum power consumption at which maximum oxygen transfer efficiency results. The oxygen transfer efficiency has maximum values when the efficiency criterion (To number) reaches an approximately constant value. The results have proven that when there are several aerators with identical diameters and the same rotational velocity but different geometrical shapes, the most efficient one will be (after having reached the maximum transfer efficiency) the one with the highest power consumption. For two aerators varying in diameter but with the same parameter as above (maximum transfer, equal rotational velocity), different efficiencies are obtained, the difference being a function of d−0.5. The results of investigating subsurface aeration systems show that the efficiency of decreased. © 1993 Wiley & Sons, Inc.
Tropane alkaloid production in Datura stramonium suspension cultures: Elicitor and precursor effects
Authors: Ballica Rabia , Ryu Dewey D. Y. , Kado Clarence I.
Published: December 2004

The effects of elicitation, carbon, and nitrogen sources, and precursors on cell growth and tropane alkaloid production in Datura stramonium cell cultures were studied. D. Stramonium cell cultures responded very well to elicitors in the late exponential phase. Addition of cell wall fragments of Phytophotora megasperma (Pmg) enhanced the final tropane alkaloid yield by fivefold compared with control culture. Supply of carbon culture. Supply of carbon and nitrogen sources, at a ratio (C/N) of up to 70, to cell cultures in the early stationary phase, suppressed tropane alkaloid production; whereas C/N rations beyond about 100 increased the final product yield by more than 100% compared to that of the control experiment. Total alkaloid production in the cell culture supplemented with phenylalanine and ornithine was five times higher that that in the control culture. Higher rations of tropine to tropic acid also stimulated alkaloid production. At a ratio of 20, the productivity was seven times higher that that in the control culture. Adding precursors at high concentrations (e.g., 3 to 10 mM) to the cell culture reduced the final cell yield by less than 40%, while elicitation did not affect the cell yield. On the other hand, cell yield in the cultures supplemented with carbon and nitrogen sources was influenced by the C/N ratio. The highest cell yield was obtained at C/N = 70. © 1993 Wiley & Sons, Inc.
Transport and intracellular accumulation of acetaldehyde in saccharomyces cerevisiae
Authors: Stanley G. A. , Pamment N. B.
Published: December 2004

The rate of acetaldehyde efflux from yeast cells and its intracellular concentration were studied in the light of recent suggestions that acetaldehyde inhibition may be an important factor in yeast ethanol fermentations. When the medium surrounding cells containing ethanol and acetaldehyde was suddenly diluted, the rate of efflux of acetaldehyde was slow relative to the rate of ethanol efflux, suggesting that acetaldehyde, unlike ethanol, may accumulate intracellularly. Intracellular acetaldehyde concentrations were measured during high cell density fermentations, using direct injection gas chromatography to avoid the need to concentrate or disrupt the cells. Intracellular acetaldehyde concentrations substantially exceeded the extracellular concentrations throughout fermentation and were generally much higher than the acetaldehyde concentrations normally recorded in the culture broth in ethanol fermentations. The technique used was sensitive to the time taken to cool and freeze the samples. Measured intracellular acetaldehyde concentrations fell rapidly as the time taken to freeze the suspensions was extended beyond 2 s. The results add weight to recent claims that acetaldehyde toxicity is responsible for some of the effects previously ascribed to ethanol in alcohol fermentations, especially Zymomonas fermentations. Further work is required to confirm the importance of acetaldehyde toxicity under other culture conditions. © 1993 John Wiley & Sons, Inc.
Oxygen transfer in a pulse bioreactor
Authors: Monahan Patrick B. , Holtzapple Mark T.
Published: December 2004

Oxygen transfer in a novel pulse bioreactor has been evaluated. The agitator consists of a series of alternately fixed and movable parallel plates mounted so that the movable plates vibrate at 30 Hz causing a pulsating fluid motion. Pure oxygen, at pressures up to 5 atm, diffuses through silicone rubber tubing that also vibrates at 30 or 60 Hz. The main feature of this bioreactor is high oxygen transfer with low shear to prevent damage to fragile animal cell membranes. We estimate that sufficient oxygen can be supplied to support over 108 cells/mL of human diploid foreskin cells growing on microcarriers. © 1993 John Wiley & Sons, Inc.
Carbon and energy balances in cell‐recycle cultures ofSchizosaccharomyces pombe
Authors: Uribelarrea J. L. , De Queiroz H. , Goma G. , Pareilleux A.
Published: December 2004

A strain of the fission yeastSchizosaccharomyces pombewas aerobically grown in a cell‐recycle fermentor under various operating conditions, i.e., different bleeding rates and various separate feed rates of glucose and basal medium. Carbon and energy balances were analyzed during steady‐state culture regimes, allowing growth yields and maintenance coefficients to be determined under glucose‐limited and glucose‐excess environments. Special attention was given to the metabolic shift from purely oxidative to respirofermentative glucose catabolism resulting from a change in the growth‐limiting factor. No maintenance requirements for the carbon source and for energy were observed during glucose‐limited culture regimes and oxidative catabolism. Under glucose excess and respirofermentative metabolism, themGcoefficient was shown to be growth‐linked, whereas the enhancement of the apparentmecoefficient observed for increased residual glucose concentrations could be assigned to a decline in the ATP yield. © 1993 John Wiley & Sons, Inc.
On the applicability of adaptive bioprocess state estimators
Authors: Lant Paul A. , Tham Ming T. , Montague Gray A.
Published: December 2004

This article presents an industrial case study, examining the application of a novel adaptive biomass estimator to an industrial microfungi production process. It is our intention that this contribution should focus upon the implementation issues of the algorithm, in preference to a rigorous theoretical development. The novel algorithm adopted is developed from Adaptive Inferential Estimation studies of Guilandoust and co‐workers. The technique utilizes input–output process measurements obtained at different frequencies, thereby providing more frequent estimates of biomass concentration than are otherwise available from off‐line laboratory analyses. The algorithm is particularly suited to the biotechnology industry, as it is capable of utilizing irregular assay measurements with varying delays.

Although this article demonstrates the encouraging industrial implications of the adaptive algorithm, like all adaptive techniques currently developed, it is restricted by the inability to perform robust on‐line system identification. The ultimate selection of a “suboptimal” “fixed parameter” algorithm for on‐line implementation, is therefore directly attributable to these inadequacies. Aspects of data acquisition, data pretreatment, and data quality are critical for real process applications, and while some practical approaches are adopted here, many important implementation problems remain unresolved. © 1993 John Wiley & Sons, Inc.
The influence of polyalcohols and carbohydrates on the thermostability of α‐amylase
Authors: de Cordt S. , Hendrickx M. , Maesmans G. , Tobback P.
Published: December 2004

The influence of polyhydric alcohols and carbohydrates on the thermostability, i.e., the heat inactivation kinetics, of Bacillus licheniformis α‐amylase was studied in the temperature range 96° to 130°C. High concentrations (from 9 to 60 weight percent) of glycerol, sorbitol, mannitol, sucrose, or starch can markedly decrease the inactivation rate constant, k, and in the studied cases, this stabilizing effect grows stronger with increasing additive concentration. Statements about stabilization should, however, be specified carefully with respect to temperature, because EA is mostly altered likewise. For dissolved enzyme EA was almost always decreased in the presence of polyol or carbohydrate, whereas for immobilized enzyme it was augmented in each studied instance. The inactivation of dissolved enzyme can, in all the studied cases, be adequately described as a firstorder process. Immobilized enzyme, however, shows biphasic then first‐order inactivation kinetics, depending on the additive concentration and temperature. © 1994 John Wiley & Sons, Inc.
Toward a self‐similar theory of microbial populations
Authors: Ramkrishna Doraiswami
Published: December 2004

A fresh quest is made of segregated cell models of microbial populations with a view to determine whether the multivarite distribution of physiological states, during transient growth, can attain self‐similar forms (i.e., become time invariant) when each physiological state variable is scaled with respect to its population average. Such self‐similar growth situations are believed to be more general than those of balanced growth. The conditions under which self‐similarity is possible are investigated. Thus conditions are stipulated on the synthesis rates of different physiological entities, cell division rate, and the partitioning of the parent cell's components among the daughter cells (assuming binary division) in order for self‐similar growth to be attained. Subject to the attainment of self‐similar growth, it is shown that cytometric data can be analyzed systematically to determine how the rates of syntheses of various biochemical entities and cell division rates vary with the physiological entities that are measured. Inverse problems, represented by algebraic systems, are identified which will potentially allow flow cytometric data to be inverted to yield quantitative information on the absolute rates of cellular growth and reproductory processes as a function of the cell states chosen for measurement. It is suggested that the methods become more effective when cytometry can be used to make direct observations on dividing cells so that the number of unknowns in the inverse problem can be reduced, thus facilitating its more complete solution. Preliminary analysis of cytometric data obtained in the literature show promise of self‐similarity and thus the possibility of application of the methods discussed here. © 1994 John Wiley & Sons, Inc.
Kinetic modeling of interesterification reactions catalyzed by immobilized lipase
Authors: Reyes Héctor R. , Hill Charles G.
Published: December 2004

Kinetic data for lipase‐catalyzed interesterification reactions between free fatty acids and triglycerides were collected and the dynamics of the interesterification reactions were successfully modeled using tow rate experssions requiring a total of five adjustable parameters. One rate expression describes the disappearance of the free fatty acid (octanoic or linolenic acid), and the second describes the rate of release of fatty acid residues from the triglycerides (olive oil or milkfat). This model is able to account for the effects of the concentration of all chemical species participating in interesterification throughout the entire reaction. When the data for both milkfat and olive oil were subjected to nonlinear regression analyses using the same mathematical model, the parameter estimates for both systems were comparable. In addition to reproducing the tendencies observed experimentally, simulations of the interesterification system under a variety of initial conditions provided insight into the effects of several reaction variables which could not be examined experimentally. Among the most significant findings of the simulation work are (1) there is a limit beyond which increasing the initial concentration of water produces no further increase in the initial rate of the interesterification reaction; (2) an increase in the initial concentration of lower glycerides produces a concomitant increase in the rate of the interesterification reaction; (3) the free fatty acids inhibit the rate of hydrolysis of the fatty acid residues of the triglycerides; (4) there is a limit beyond which increasing the initial concentration of triglycerides produces no significant increase in the rate of either the hydrolysis reaction or the interesterification reaction. © 1994 John Wiley & Sons, Inc.
EPR characterizations of α‐chymotrypsin active site dynamics in reversed micelles at enhanced gas pressures and after subjection to clathrate formation conditions
Authors: Kommareddi Nagesh S. , O'Connor Kim C. , John Vijay T.
Published: December 2004

Electron paramagnetic resonance spectroscopy is used to characterize the active site dynamics of α‐chymotrypsin solubilized in reversed micelles. Of particular interest is the behavior of the enzyme when the micellar system is subjected to enhanced gas pressures and low temperatures. At specific thermodynamic conditions, clathrate hydrates from from the intramicellar water, reducing the micelle size and water content. Also, beyond a critical pressure, micellar instbility results. The EPR spectra under these conditions indicate that the rotational correlation times increase appreciably only when the water‐to‐surfactant molar ratio, W0, is reduced to values lower than 10. The EPR characterization also reveals a remarkable resilience of the enzyme when subjected to pressure‐induced changes; when returned to ambient conditions, activity and active site dynamics are fully restored. © 1994 John Wiley & Sons, Inc.
Sorption and precipitation of metals in activated sludge
Authors: Kodukula Prasad S. , Patterson James W. , Surampalli Rao Y.
Published: December 2004

A conceptual model describing the relative roles of sorption and precipitation processes for metals in solid‐solution suspensions is presented. The model performance is demonstrated using experimental data on sorption and precipitation of metals in samples of activated sludge mixed liquor. Based on the experimental results presented here, it appears that, at total metal and mixed liquor suspended solids concentrations and pH values generally encountered in full‐scale municipal (or combined municipal/industrial) activated sludge systems, metals are primarily removed by sorption processes.
Lipase catalyzed esterification of glycidol in nonaqueous solvents: Solvent effects on enzymatic activity
Authors: Martins João F. , de Sampaio Teresa Correaêa , de Carvalho Inê Borges , Barreiros Susana
Published: December 2004

We studied the effect of organic solvents on the kinetics of porcine pancreatic lipase (pp) for the resolution of racemic glycidol through esterification with butyric acid. We quantified ppl hydration by measuring water sorption isotherms for the enzyme in the solvents/mixtures tested. The determination of initial rates as a function of enzyme hydration revealed that the enzyme exhibits maximum apparent activity in the solvents/mixtures at the same water content (9% to 11% w/w) within the associated experimental error. The maximum initial rates are different in all the media and correlate well with the logarithm of the molar solubility of water in the media, higher initial rates being observed in the solvents/mixtures with lower water solubilities. The data for the mixtures indicate that ppl apparent activity responds to bulk property of the solvent. Measurements of enzyme particle sizes in five of the solvents, as function of enzyme hydration, revealed that mean particle sizes increased with enzyme hydration in all the solvents, differences between solvents being more pronounced at enzyme hydration levels close to 10%. At this hydration level, solvents having a higher water content lead to lower reaction rates; these are the solvents where the mean enzyme particle sizes are greater. Calculation of the observable modulus indicates there are no internal diffusion limitations. The observed correlation between changes in initial rates and changes in external surface area of the enzyme particles suggests that interfacial activation of ppl is only effective at the external surface of the particles. Data obtained for the mixtures indicate that ppl enantioselectivity depends on specific solvent‐enzyme interactions. We make reference to ppl hydration and activity in supercritical carbon dioxide. © 1994 John Wiley & Sons, Inc.
Artificial neural network based experimental design procedure for enhancing fermentation development
Authors: Glassey J. , Montague G. A. , Ward A. C. , Kara B. V.
Published: December 2004

Conventional experimental design techniques are available to assist in the optimization of fermentation processes, but due to the nonlinearities in the bioprocess, they are limited in their effectiveness. This problem is further complicated with recombinant systems as a result of the additional complexities of the process. This article describes a general strategy using artificial neural networks as an alternative approach to fermentation process development laboratory are presented for the neural network based procedures. © 1994 John Wiley & Sons, Inc.
DSC and protein–based time‐temperature integrators: Case study of α‐amylase stabilized by polyols and/or sugar
Authors: De Cordt S. , Avila I. , Hendrickx M. , Tobback P.
Published: December 2004

Differential scanning calorimetry (DSC) was used as a tool for rapid assay of the thermostability of two Bacillus sp. α‐amylases and horseradish peroxidase as a function of the concentration of glycerol, sorbitol, and sucrose. In this screening study, the DSC peak temperature proved to be a good measure of protein thermostability. By means of isothermal heating experiments, the kinetics of heat decay of B. amyloliquefaciens α‐amylase were studied by following the course of the DSC peak area (heat exchange (ΔH/wt)) as a function of time. The high stability of this enzyme in the presence of polyolic alcohols or carbohydrates allowed working at temperatures as high as 127°C. The results of this study can have particular relevance with regard to research on and development of protein‐based time‐temperature integrators (TTls) for evaluating heat pasteurization or sterilization treatments of foods or pharmaceutical products. The use of the DSC peak area (ΔH.wt) as TTI‐response was validated in experiments with a time‐variable temperature profile. Finally, it was shown how the results of such non‐isothermal experiments can even be used for (re‐) estimation of the protein decay kinetic parameters (k, EA). © 1994 John Wiley & Sons, Inc.
Modification of central metabolic pathway in escherichia coli to reduce acetate accumulation by heterologous expression of the bacillus subtilis acetolactate synthase gene
Authors: Aristidou Aristos A. , San Ka‐Yiu , Bennett George N.
Published: December 2004

A novel metabolic engineering technique involving the redirection ofcellular carbon fluxes was employed to reduce acetate production in an Escherichia coli culture. Metabolic engineering was achieved by cloning E. coli the gene for the Bacillus subtilis acetolactate synthase (ALS), an enzyme capable of catalyzing the conversion of pyruvate to nonacidic and less harmful species. The heterologous expression of the ALS catabolic enzyme in Escherichia coli drastically modified the cellular glycolytic fluxes. In particular, acetate excretion, which is a common characteristic of E. coli, as well as a physiological burden, was minimized. The residual acetate level was kept under control and maintained at a level that was below the toxic threshold. The expression of the biologically active ALS enzyme in E. coli did not result in any detectable changes on either cell growth rate or cell yields. The alternative product, acetoin, was shown to be 50 times less harmful than acetate. Similarities in the growth pattern of two different E. coli strains, RR1 and GJT001, under all cultivation conditions suggested that the ability of ALS to reduce acetate accumulation is generic and not strain‐specific. © 1994 John Wiley & Sons, Inc.
Removal of cytokines from HAS‐containing solutions by adsorption onto silica
Authors: Hei D. J. , El Kalay M. A. , Lin A. T. T. , Kshirsagar B. , Okarma T. B. , Blanch H. W.
Published: December 2004

Septic shock syndrome is a potentially fatal medical condition that is associated with elevated blood levels of low molecular weight proteins known as cytokines. Adsorption was investigated as a potential method for removing cytokines from blood. Saline with 50 mg/mL human serum albumin (HAS) spiked with pathological concentrations (ng‐pg/mL) of radiolabeled cytokine was used to study cytokine adsorption. Adsorption isotherms were linear in the pathological concentration range, with adsorption constants ranging from 33.0 mL/g to 173 mL/g for tumor necrosis factor (TNF‐α), interleukin‐8 (IL‐8),interleukin‐6 (IL‐6), and C3a. Adsorption constants were also determined for interleukin‐1α (IL‐1α), IL‐1β, and interferon‐γ (IFN‐γ). The adsorption of cytokines by several different silica adsorbents was investigated. Increased concentrations of NaCl reduced cytokine adsorption, but did not completely eliminate adsorption even at high concentrations, suggesting that adsorption wads not entirely electrostatic in nature. Possible mechanisms of cytokine adsorption are discussed. Data for batch adsorption for TNF‐α was used to estimate the minimum amount of silica required to treat septic shock. It was concluded that a silica adsorbent has a sufficiently high capacity to be used for hemoperfusion. Adsorption of myoglobin and cytochrome c was also investigated as possible marker proteins for future dynamic adsorption studies in hemoperfusion devices. © 1994 John Wiley & Sons, Inc.
Viability and protein secretion from human Hepatoma (HepG2) cells encapsulated in 400‐μm polyacrylate microcapsules by submerged nozzle–liquid jet extrusion
Authors: Uludag Hasan , Horvath Vlad , Black John P. , Sefton Michael V.
Published: December 2004

An interfacial precipitation process to encapsulate mammalian cells in hydroxyethyl methacrylate‐methyl methacrylate (HEMA‐MMA) microcapsules of ∼ 750 in ∼m diameter was previously described. It was not possible to produce smaller capsules due to low shearing force. A new droplet generation scheme was developed by suspending the cell and polymer co‐extrusion nozzle in a uniform co‐axial fluid jet which enabled the production of 300 to 600‐µm diameter capsules. HepG2 hepatoma cells in 400‐µm‐diameter HEMA‐MMA capsules were able to retain their metabolic activity during and after the encapsulation process. The in vitro secretion of plasma proteins α1‐acid glycoprotein, α1‐antitrypsin, and fibrinogen by the encapsulated cells was retained. The encapsulated cells secreted less fibrinogen (340 kD) relative to α1‐acid glycoprotein (42kD), indicating the sieving effect (but not absolute cut‐off) of the HEMA‐MMA membrane. © 1994 John Wiley & Sons, Inc.
Bubble bed reactor: A reactor design to minimize the damage of bubble aeration on animal cells
Authors: Sucker H. G. , Jordan M. , Eppenberger H. M. , Widmer F.
Published: December 2004

A new bubble aeration system was designed to minimize cell killing and cellular damage due to sparging. The residence time of the bubbles in the developed bubble bed reactor was prolonged dramatically by floating them in a countercurrent produced by an impeller. The performance of the new reactor bubble aeration system, implemented in a laboratory reactor, was tested in dynamic aeration experiments with an without cells. An efficiency up to 95% in oxygen transfer could be achieved, which enables a much lower gas flow rate compared with conventional bubble aeration reactors. The low gas flow rate is important to keep cell damage by bubbles as low as possible. A laser light sheet technique used to find the optimal flow pattern in the reactor. The specific power dissipation of the impeller is a good measure to predict cell damage in a turbulent flow. Typical values for the power dissipation measured in the bubble bed reactor were in the range of 0.002 to 0.013 W/kg, which is far below the critical limit for animal cells. The growth of a hybridoma cell line was studied in cell cultivation experiments. A protein‐free medium without supplements such as serum or Pluronic F68 was used to exclude any effect of cell‐protecting factors, No difference in the specific growth rate and the yield of the antibodies was observed in cell grown in the bubble free surface aeration in the spinner flask. In contrast to the spinner flask, however, the bubble bed reactor design could be scaled up. © 1994 John Wiley & Sons, Inc.
Surfactant structure effects in protein separations using nonionic microemulsions
Authors: Vasudevan Madhavan , Tahan Kim , Wiencek John M.
Published: December 2004

In this article, the extraction of cytochrome c utilizing various nonionic surfactant microemulsions has been tested to determine the effect of surfactant structure on protein partitioning. Surfactants tested include a linear alcohol ethoxylate (Neodol 91–2.5), two alkyl phenol ethoxylates (lgepal CO‐520, Trycol 6985), and a series of alkyl sorbitan esters that are either ethoxylated (Tweens) or un‐ethoxylated (Spans). Initial attempts to extract hemoglobin into Neodol 91–2.5 Winsor II microemulsions (oil‐continuous) appeared successful based on heme estimation. Careful analysis showed that the hemoglobin had dissociated prior to extraction and that only the heme was extracted with false positive results. In fact, Neodol 91–2.5 microemulsions were unable to extract a variety of proteins with differing biophysical properties. Among all the other nonionic surfactant microemulsions tested only those made using sorbitan esters extracted significant amounts of cytochrome c. The partition coefficients achieved in this study are more than an order of magnitude higher than that seen previously in the literature for comparable sorbitan systems. However, this partition coefficient is extremely sensitive to ionic strength. At an ionic strength as low as 0.001 M, the partition coefficient is reduced to that seen in previous studies. We have found that protein partitioning in sorbitan ester microemulsions is not a function of water content. In addition, extraction is not a function of either alkyl chain length, or polyethylene oxide molecular weight. Hence, the sorbitan group appears to have an important role in extraction, possibly through a weak electrostatic protein–surfactant interaction. © 1995 John Wiley & Sons, Inc.
A reagentless amperometric electrode based on carbon paste, chemically modified with D‐lactate dehydrogenase, NAD+, and mediator containing polymer for D‐lactic acid analysis. I. Construction, composition, and characterization
Authors: Shu Hun‐Chi , Mattiasson Bo , Persson Björn , Nagy Geza , Gorton Lo , Sahni Suresh , Geng Lin , Boguslavsky Leonid , Skotheim Terje
Published: December 2004

A reagentless carbon paste electrode was designed for D‐lactic acid analysis in a flow injection system for the monitoring of the production of D‐lactate in a batch fermentation. D‐Lactate dehydrogenase, nicotinamide adenine dinucleotide (NAD+), a synthetic redox polymer containing covalently attached toluidine blue O as mediator, graphite powder, and paraffin oil were used for the construction of the modified carbon paste electrode. D‐Lactate selectivity was indicated by insignificant responses from a variety of possible interfernces including L‐lactate. The electrodes gave a linear response in the range between 0.05 and 5 mM D‐lactate, with a detecting limit of 30 μM, allowing a sample throughput of 20 h−1. Preliminary investigations were made by covering the electrode surface with electropolymerized membranes. Satisfactory stability was observed, indicated by a reproducibility of 3.3% relative standard deviation (RSD, n = 31), with a non‐membrane‐covered electrode for the analysis of D‐lactate in fermentation broth. A long‐term stability (230 broth samples) was proven, suggesting the electrodes to have a good potential for use in on‐line monitoring of fermentation processes. © 1995 John Wiley & Sons, Inc.
Membrane‐attached biofilms for VOC wastewater treatment. II: Effect of biofilm thickness on performance
Authors: dos Santos L. M. Freitas , Livingston A. G.
Published: December 2004

This article reports a study of the performance of membrane‐attached biofilms grown in a single tube extractive membrane bioreactor (STEMS) used for the treatment of a synthetic wastewater containing a toxic VOC (1,2‐dichloroethane [DCE]). Mass balances show that complete mineralization of DCE was achieved, and that the biofilms were effective in reducing air stripping to negligible levels. Experimental results are presented showing the evolution over time of biofilm thickness and its influence on the flux of DCE across the membrane. It has been found that a trade‐off exists between the positive influence of biofilms in reducing air‐stripping of DCE, and the negative influence of biofilms in reducing DCE flux across the membrane. These considerations lead to an optimal biofilm thickness in the region of 200 to 400 μm being recommended for this system. © 1995 John Wiley & Sons, Inc.
Relationship between loss of heavy chains and the appearance of nonproducing hybridomas
Authors: Couture Michelle L. , Heath Carole A.
Published: December 2004

One drawback to the in vitro production of monoclonal antibodies is the loss of productivity exhibited by hybridomas over time, which has been shown to correspond to the appearance of a nonproducing subpopulation. In this study, we monitored the presence of antibody components, both intra‐ and extracellular, between producing and nonproducing hybridomas. A nonproducing cell population appeared which lacked heavy chain, while all cultures continued to produce light chain, indicating that the loss in antibody production resulted from the absence of heavy chain and occurred before protein assembly or secretion. © 1995 John Wiley & Sons, Inc.
Formation of nitrifying biofilms on small suspended particles in airlift reactors
Authors: Tijhuis L. , Huisman J. L. , Hekkelman H. D. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: December 2004

For a stable and reliable operation of a BAS‐reactor a high, active biomass concentration is required with mainly biofilm‐covered carriers. The effect of reactor conditions on the formation of nitrifying biofilms in BAS‐reactors was investigated in this article. A start‐up strategy to obtain predominantly biofilm‐covered carriers, based on the balancing of detachment and a biomass production per carrier surface area, proved tp be very successful. The amount of biomass and the fraction of covered carrier were high and development of nitrification activity was fast, leading to a volumetric conversion of 5 kgN · m−3 · d−1 at a hydraulic retention time of 1h. A 1‐week, continuous inoculation with suspended purely nitrifying microorganisms resulted in a swift start‐up compared with batch addition of a small number of biofilms with some nitrification activity. The development of nitrifying biofilms was very similar to the formation of heterotrophic biofilms. In contrast to heterotrophic bio‐films, the diameter of nitrifying biofilms increased during start‐up. The detachment rate from nitrifying biofilms decreased with lower concentrations of bare carrier, in a fashion comparable with heterotrophic biofilms, but the nitrifying biofilms were much more robust and resistant. Standard diffusion theory combined with reaction kinetics are capable of predicting the activity and conversion of biofilms on small suspended particles. © 1995 John Wiley & Sons Inc.
Comparison of hydrolysis and esterification behavior of Humicola lanuginosa and Rhizomucor miehei lipases in AOT‐stabilized water‐in‐oil microemulsions: II. Effect of temperature on reaction kinetics and general considerations of stability and productivity
Authors: Crooks Gavin E. , Rees Gareth D. , Robinson Brian H. , Svensson Martin , Stephenson G. Richard
Published: December 2004

Humicola lanuginosa lipase (HIL) and Rhizomucor miehei lipase (RrnL), isolated from commercial preparations of Lipolase and Lipozyme, respectively, were solubilized in AOT‐stabilized water‐in‐oil (w/o) microemulsions in n‐heptane and aspects of their hydrolysis and condensation activity examined. The temperature dependence of HIL hydrolysis activity in unbuffered R = 10 microemulsions matched very closely that for tributyrin hydrolysis by Lipolase in an aqueous emulsion assay. Apparent activation energies were measured as 13 ± 2 and 15 ± 2 kJ mol / respectively. Condensation activity, however, was essentially independent of temperature over the range 5° to 37°C. The stability of HIL over a 30‐day period was very good at all pH levels (6.1, 7.2, 9.3) and R values studied (5, 7.5, 10, 20), except when high pHs and low R values were combined. The excellent stability was reflected by the linearity of the productivity profiles which facilitate system optimization. The temperature dependence of RmL hydrolysis activity toward pNPC4 showed a maximum at 40°C and an apparent Eact = 20 ± 2 kJ mol−1 was calculated based on the linear region of the profile (5° to 40°C). RmL esterification activity showed only a slight dependence on temperature over the studied range (0° to 40°C) and an apparent Eact = 5 ± 1 kJ mol−1 was measured for octyl decanoate synthesis. Both RmL and HIL, therefore, have potential for application in low temperature biotransformations in microemulsion‐based media. The stability of RmL over a 30‐day period was good in R = 7.5 and R = 10 microemulsions containing pH 6.1 buffer, and this was reflected in the linearity of their respective productivity profiles. RmL stability was markedly poorer at more alkaline pH, however, and proved to be sensitive to relatively small changes in the R value. © 1995 John Wiley & Sons, Inc.
Einige Probleme des Stoff‐ und Wärmeüberganges an Grenzflächen
Authors: Wicke E.
Published: December 2004

Die im folgenden erörterten Fragen sind nicht nur deswegen Grenzprobleme, weil es sich bei ihnen um Transportvorgänge durch Phasengrenzen handelt. Vielmehr bildet dieses Gebiet auch eine Berührungsgrenze zwischen den Ingenieurwissenschaften und der physikalischen Chemie. Von erstgenannter Seite wurde der betreffende Fragenkreis in letzter Zeit mehrfach zusammenfassend dargestellt1. Hier möge er mehr vom Standpunkt der physikalischen Chemie aus und unter Bevorzugung der bisher noch nicht befriedigend gelösten Probleme behandelt werden. Gerade dieses Gebiet ist besonders geeignet, die Fruchtbarkeit einer Zusammenarbeit beider Wissenschaften im Rahmen der Verfahrenstechnik aufzuzeigen.
Über die Bestimmung der Wärmeleitfähigkeit, der Wärmekapazität und der Wärmeeindringzahl in einem Kurzzeitverfahren
Authors: Krischer O.
Published: December 2004

Beschrieben werden ein Verfahren sowie eine Meßanordnung, mit denen die Wämeleitfähigkeit λ, die Wärmekapazität cλ und die Wärmeeindringzahl \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt {\lambda c\gamma } $\end{document} in einem Kurzversuch gleichzettig bestimmt werden können.
Tantal als Werkstoff im chemischen Apparatebau
Authors: Meyll Herbert , Speidel Hermann
Published: December 2004

Tantal ist wegen seiner hervorragenden Korrosionseigenschaften als Konstruktionsmaterial für den chemischen Apparatebau, gerade bei ausgefallenen Beanspruchungen, oft das einzige Material, das auch aus wirtschaftlichen Gründen anwendbar ist. Zahlreiche Beispiele zeigen die Entwicklung in den letzten Jahren.
Die Diffusion von Wasser in Kunststoffe
Authors: Jouwersma C.
Published: December 2004

Die Feuchtigkeitsaufnahme und Feuchtigkeitspermeation ist für viele Anwendungsgebiete der Kunststoffe wichtig, z. B. für die Elektroindustrie, bei der bestimmte Schaltungsteile mit einer Kunststoffschicht vor Wasser geschützt werden. Der bisher übliche Brauch, die Wasseraufnahme eines Materials mit einer Zahl, etwa nach der betreffenden Norm, zu kennzeichnen, gestattet es nicht, Aussagen über die Wasser‐aufnahme zu machen, wenn die Verhältnisse von denen der Norm verschieden sind. Dazu ist eine nähere Kenntnis des ihr zugrunde liegenden physikalischen Vorganges unbedingt notwendig. Es stellt sich heraus, daß sich die Feuchtigkeitsaufnahme durch die klassische Diffusionstheorie in durchaus befriedigender Weise erfassen läßt. Ein einfacher mathematischer Eingriff ermöglicht es, die Variablen Form und Größe des Körpers, die Art des Mediums, die Lagerungszeit und ‐temperatur und die Material‐konstanten zu trennen und also Voraussagen über die Wasseraufnahme eines Körpers von beliebiger Größe und Gestalt bei ebenfalls beliebiger Wahl der übrigen Bedingungen zu machen.
Wärmeübergang an Gase in Füllkörper‐ und Kontaktrohren
Authors: Schumacher R.
Published: December 2004

Die den Wärmeübergang in Füllkörper‐ und Kontaktrohren bestimmenden EinflußGrößen wurden gesichtet, wobei eine Korrelation der bisher bekannten Versuchsergebnisse möglich wird. Die auf den Rohrdurchmesser bezogenen Reynolds‐Zahlen Re < 1600 bzw. Re = 1600 bis 10 000 bzw. Re > 10 000 kennzeichnen drei Strömungsbereiche, in denen der Einfluß der Rohrlänge auf den Wärmeübergang verschieden groß ist. Ein optimaler Wärmeübergang liegt für alle Strömungsbereiche dann vor, wenn der Durchmesser des Füllmaterials 1/8 des Rohrdurchmessers beträgt

Gekürzt werden die Ergebnisse dieser Arbeit in Form von Berechnungsdiagrammen in den VDI‐Wärmeatlas aufgenommen.

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Wasserstoff‐Überspannung am Quecksilber bei der Chloralkali‐Elektrolyse
Authors: Hauck Gerhard
Published: December 2004

Es wurde der Einfluß einzelner Elemente in Kaliumchlorid‐Solen auf die Wasserstoff‐Überspannung durch Abscheidung an einem Quecksilber‐Tropfen bei – 1,9 V untersucht. An dem kleinen Quecksilber‐Tropfen reichern sich die Störelemente an und katalysieren die Wasserstoff‐Abscheidung, die mit einem Mikroskop beobachtet wurde. Es wurde versucht, die Störelemente durch anodische Amalgam‐Voltametrie in Menge und Art zu bestimmen.
Das Zusammenwirken von Diffusion und chemischer Reaktion in überströmten, katalytisch aktiven Pulverschüttungen, Preßlingen und Sinterlingen
Authors: Menold Richard
Published: December 2004

Für den Fall der überströmten, katalytisch aktiven Pulverschüttung wird das Zusammenwirken von Transportvorgängen und dem eigentlichen chemischen Reaktionsgeschehen mathematisch so erfaßt, daß die Berechnung der Geschwindigkeitskonstanten und der Reaktionsordnung aus experimentell zugänglichen Daten möglich ist. Zur Berechnung des Nutzungsgrades werden Beziehungen angegeben, die nur von drei dimensionslosen, dem Experiment zugänglichen Größen abhängen. Es wird gezeigt, daß sich die für die Schüttung erhaltenen Ergebnisse auf den plattenförmigen Katalysator (Preßling, Sinterling) übertragen lassen. Auf Grund der Resultate kann die nach jeder katalytischen Messung auftauchende Frage, inwieweit die Meßergebnisse durch Diffusionseffekte beeinflußt wurden, für Schüttungen, Preßlinge und Sinterlinge beantwortet werden.
Erzeugung von Acetylen durch thermische Spaltung von Kohlenwasserstoffen mittels hocherhitzten Wasserstoffes. (WLP‐Verfahren der Knapsack‐Griesheim AG)
Authors: Sennewald Kurt , Schallus Erich , Pohl Franz
Published: December 2004

Als Energieträger für die Spaltung von Kohlenwasserstoffen wird im Lichtbogen hocherhitzter und teilweise atomarer Wasserstoff verwendet. Zur Umsetzung wird ein Überschuß an gasförmigem Kohlenwasserstoff, z. B. verdampftes Benzin, von ca. 15% verwendet. Dieser wird zusammen mit den Nebenprodukten der Spaltung wieder zugeführt, so daß als Endprodukte nur Acetylen, Äthylen, Methan und Wasserstoff erhalten werden. Die Ausbeute an Acetylen und Äthylen beträgt bei Verwendung von Benzin über 70 Gew.‐%. Bei einem Produktionsverhältnis von 55 Teilen Acetylen : 45 Teilen Äthylen beträgt der effektive Energieverbrauch 4,5 kWh für 1 kg Acetylen/Äthylen‐Gemisch im Spaltgas. Im Gegensatz zu anderen Verfahren, bei denen die Spaltenergie durch Verbrennen von Kohlenwasserstoffen oder Wasserstoff mit Sauerstoff erzeugt wird, enthält das Spaltgas weder Kohlendioxyd noch Kohlenoxyd, weder Wasserdampf noch peroxydische Verbindungen. Es ist daher auch praktisch frei von Teer und Polymerisaten. Die Aufarbeitung des Spaltgases wird dadurch sehr vereinfacht. Es wird erwartet, daß das Acetylen, auf petrochemischer Grundlage nach diesem Verfahren in Anlagen großer Kapazität hergestellt, seine Konkurrenzfähigkeit zum Äthylen wiedergewinnen wird.