bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics studies in a continuous steady state hollow fiber membrane enzyme reactor
Authors: Davis James C. 
Published: December 2004

AbstractPorous hollow cellulose fibers have been used to separate a nonflowing enzyme solution of alkaline phosphatase from a continuous flow of substrate. The porosity of the hollow fiber membrane allows the substrate and product to diffuse freely through the membrane while restricting the permeation of the enzyme. The resulting “immobilized” enzyme system has been shown to behave as a continuous reactor—converting p‐nitrophenylphosphate to p‐nitrophenol. By varying the concentrations, flow rate, etc., either diffusion or enzyme kinetics can be studied. The continual influx of product and removal of substrate at steady state allows the study of kinetics of relatively short half‐life enzymes and unstable systems.
An enzyme rate equation for the overall rate of reaction of gel‐immobilized glucose oxidase particles under buffered conditions. I. Pseudo‐one substrate conditions
Authors: Atkinson B. , Lester D. E. 
Published: December 2004

AbstractThe overall rate of reaction of buffered gel‐immobilized glucose oxidase particles is described by means of an enzyme rate equation which relates the overall reaction rate of a particle to the free solution characteristics of the enzyme, the effective diffusivity of the limiting substrate in the gel, the characteristic particle size, and the limiting substrate concentration adjacent to the gel surface. This equation accounts quantitatively for the limitation of the overall rate of reaction by substrate diffusion, and it is used to illustrate the influence of the system parameters, i. e., particle size, enzyme concentration, and pH, on the extent of the diffusional resistance associated with gel‐immobilized glucose oxidase particles.The enzyme rate equation is generally applicable to those enzymes whose kinetics approximately follow Michaelis‐Menten form when in free solution.
Simple system for controlling dissolved oxygen concentration in laboratory fermentors
Authors: Fuchs Renato , Wang Daniel I. C. 
Published: December 2004

AbstractA simple system for the control of oxygen transfer in laboratory fermentation units has been devised. This system employs pure oxygen to elevate the driving force for oxygen transfer. In addition, the aeration is controlled in a closed loop manner in order to minimize total exit flow of the gas from the fermentor. Fermentation study using Bacillus stearothermophilus grown on n‐dodecane at 55°C illustrates excellent carbon recovery as well as the ease of controlling oxygen transfer.
Studies on immobilized trypsin in high concentrations of organic solvents
Authors: Weetall Howard H. , Vann William P. 
Published: December 2004

AbstractTrypsin was covalently immobilized on porous glass in the presence and absence of a specific substrate and reacted in various organic solvents of different dielectric constants. Optimum solvent concentration, pH profile, Km(app), Vmax(app), productivity versus temperature, activity, and reaction rates were determined. Reaction rates of six lysyl dipeptides were compared. Crystalline trypsin was dansylated for studies by nanosecond fluorescence techniques to determine the effects of introducing high concentrations of organic solvents on the molecule. The results indicated that greater reaction rates were observed with dipeptides having more acidic carboxyl terminal groups. The data also indicated that greater reaction rates were observed in higher concentrations of solvents of lower dielectric constants. Nanosecond fluorescence spectroscopy of trypsin in high concentrations of a low dielectric constant solvent indicated major dehydration even though maximal enzyme‐activity was achieved under these conditions.
Maximization of steady‐state Bacterial production in a chemostat with pH and substrate control
Authors: Spitzer David William 
Published: December 2004

AbstractThis analytical study deals with the steady‐state behavior and control of microbial growth in continuous cultures. A second order Haldane‐Monod model of continuous cultures is used as a basis for study of the effects of the adjustment of pH by the addition of acidic (or basic) materials. The treatment of a hydrogen ion concentration, in addition to substrate and microbial concentrations as state variables, results in a third order system of equations describing the process.The analysis of the system in equilibrium yields several admissible steady states, that is, steady states which satisfy all constraints. An optimal control problem is formulated and subsequently solved to maximize steady‐state microbial production.
Parameters in the construction of an immobilized dual enzyme catalyst
Authors: Bouin James C. , Atallah Mokhtar T. , Hultin Herbert O. 
Published: December 2004

AbstractThe glucose oxidase and catalase activities immobilized to the γ‐aminopropyltriethoxysilane derivative of nickel‐impregnated silica alumina was controlled by several factors. The most important of these was enzyme concentration. In constructing the dual immobilized enzyme catalyst, competition between the two enzymes for available binding sites was observed. The order of addition of the various reactants during immobilization was also important. Higher glucose oxidase activities were immobilized when glutaraldehyde was added concurrently with the enzyme, while maximal coupling of catalase occurred if glutaraldehyde was first added to react with the amino derivative of the silica alumina support, excess reagent washed away, and then the catalase added. Bovine serum albumin, which aids in the crosslinking of glucose oxidase, hindered the coupling of the enzyme to the support particles.
Influence of pH and temperature on the substrate yield coefficient of yeast growth in a chemostat
Authors: Eroshin V. K. , Utkin I. S. , Ladynichev S. V. , Samoylov V. V. , Kuvshinnikov V. D. , Skryabin G. K. 
Published: December 2004

AbstractThe influence of pH and temperature on the substrate yield coefficient for growth of Saccharomyces cerevisiae in a chemostat under limited organic substrate conditions was studied.Mathematical analysis of the substrate yield coefficient as a function of pH and temperature in the near‐optimal area was made. It was shown that the location of pH and temperature optima were independent of each other. The maximum substrate yield coefficient had the following coordinates: pH = 4.1, temperature = 28.5°C.
Influence of salts and gelatin on disintegration of Saccharomyces cerevisiae by freeze‐pressing
Authors: Magnusson K.‐E. , Edebo L. 
Published: December 2004

AbstractThe disintegration by freeze‐pressing of a low concentration of Saccharomyces cerevisiae suspended in aqueous solutions of gelatin and different salts has been studied at different temperatures. In the freeze‐pressing process deionized water and salt solutions flow in pulses, whereas samples with increasing concentrations of gelatin or cells tend to flow more smoothly. This smooth flow enhances the disruption efficiency particularly at lower temperatures, which seems to be of great practical importance. The addition of salts also promotes disintegration. The presence of both gelatin and salts works antagonistically on disintegration presumably because of different modes of action at disruption of cells.
Feather protein as a support for immobilizing enzymes
Authors: Stanley W. L. , Watters G. G. , Chan B. G. , Kelly S. H. 
Published: December 2004

AbstractFeather meal protein was prepared in granular form and used as a support for lactase using glutaraldehyde as the crosslinking agent. The support gave a high retention of activity and in column operation it yielded apparent half‐lives from 50 to 100 days. Because of its gel‐like consistency (water content of about 90%), there is some diffusional restricting of activity as indicated by the kinetic data of soluble and immobilized enzymes.
Application of dynamic calorimetry for monitoring fermentation processes
Authors: Mou Duen‐Gang , Cooney Charles L. 
Published: December 2004

AbstractThe rate of heat evolution (kcal/liter‐hr) in mycelial fermentations for novobiocin and cellulase production with media containing noncellular solids was measured by an in situ dynamic calorimetric procedure. Thermal data so obtained have proved significant both in monitoring cell concentration during the trophophase (growth phase) and in serving as a physiological variable in the fermentation process. The validity of this technique has been demonstrated by closing the overall material and energy balances.The maintenance energy in a batch fermentation can also be calculated by integrating heat evolution data. This integration method is applicable to a fermentation lacking a precise cell growth curve. The maintenance coefficient, obtained for the novobiocin fermentation by Streptomyces niveus, is equal to 0.028 g glucose equivalent/g cell‐hr. The production of novobiocin in the idio‐phase (production phase) also correlates well with the amount of energy catabolixed for maintenance and this results in an observed conversion yield of glucose to novobiocin of 11.8 mg of novobiocin produced per gram of glucose catabolized.A new physiological variable, kilocalories of heat evolved per millimole of oxygen consumed, has been proposed to monitor the state of cells during the fermentation. This method may provide a simple way to monitor on‐line shifts in the efficiency of cell respiration and changes in growth yields during a microbial process.
Physical characteristics of porous cellulose beads as supporting material for immobilized enzymes
Authors: Chen Li Fu , Tsao George T. 
Published: December 2004

AbstractCellulose beads prepared in this report have high porosity (75–80%) and evenly distributed pores. The pore size is about 1000 Å. The cellulose beads are physically strong and contain large amounts of reactive groups, making them suitable for use as carriers for immobilized enzymes.
Heat transfer coefficients and two‐phase dispersion properties in a stirred‐tank fermentor
Authors: Pollard R. , Topiwala H. H. 
Published: December 2004

AbstractExperiments were performed in a pilot scale 0.30 m3 conventional stirred‐tank fermentor using water, air/water, and air/K2SO4 solutions. Both single‐ and two‐stage impeller systems were investigated. Overall and tank‐side coefficients for heat transfer from a 0.012 m diameter coil were measured for a range of impeller speeds and superficial gas velocities. Power input, bubble size, and gas hold‐up were also determined. An analysis of the experimental results indicates that previously published correlations for single‐phase heat transfer in stirred tanks (of the type: Nu = C(Re)α(Pr)β) are not applicable for single‐ or multiimpeller gas/liquid systems. The introduction of air alters the mixing pattern significantly, affecting both average and local tank‐side heat transfer coefficients. Power input and gas hold‐up are suggested as the major correlating parameters for the determination of tank‐side heat transfer coefficients.
Application of polylysine bound succinyl‐NA to a membrane reactor
Authors: Yamazaki Y. , Maeda H. , Suzuki H. 
Published: December 2004

AbstractThe amide bond at N‐6 in succinyl‐NAD was found to be more stable than in former accounts. Succinyl‐NAD was coupled on polylysine to give a new polymer derivative of NAD, which retained at least 85% of the initial coenzymic activity even after dialysis for one week. The polymer derivative of NAD could be applied to a membrane reactor containing alcohol dehydrogenase and lactate dehydrogenase and lactate was continuously produced in a half‐life of ten days.
Analysing the factors influencing clean technology adoption: a study of the Spanish pulp and paper industry
Authors: del Río González Pablo 
Published: January 2005

AbstractTechnological change has a relevant role to play in the transition towards a sustainable industry. However, slow diffusion of clean technologies can be observed in OECD countries. The analysis of the determinants and barriers to clean technology adoption should be a main goal of economists and social scientists. This paper shows that three sets of interrelated factors prevent but also stimulate the widespread adoption and diffusion of clean technology: these are factors external and internal to the firm, conditions of the potential adopters and characteristics of the environmental technology. These factors are included in the so‐called ‘triangular model’, which is further applied to the analysis of clean technology adoption in the pulp and paper industry in Spain. The empirical study shows that clean technology adoption decisions are the result of an interaction between these factors, often involving contradictory signals for the potential adopter. The paper closes with some public policy recommendations for the effective and efficient promotion of clean technology diffusion. Copyright © 2005 John Wiley & Sons, Ltd and ERP Environment.
Reduced mitotic activity at the periphery of human embryonic stem cell colonies cultured in vitro with mitotically‐inactivated murine embryonic fibroblast feeder cells
Authors: Heng Boon Chin , Cao Tong , Liu Hua , Rufaihah Abdul Jalil 
Published: January 2005

AbstractThis study attempted to investigate whether different levels of mitotic activity exist within different physical regions of a human embryonic stem (hES) cell colony. Incorporation of 5‐bromo‐2‐deoxyuridine (BrdU) within newly‐synthesized DNA, followed by immunocytochemical staining was used as a means of detecting mitotically‐active cells within hES colonies. The results showed rather surprisingly that the highest levels of mitotic activity are primarily concentrated within the central regions of hES colonies, whereas the peripheral regions exhibited reduced levels of cellular proliferation. Two hypothetical mechanisms are therefore proposed for hES colony growth and expansion. Firstly, it is envisaged that the less mitotically‐active hES cells at the periphery of the colony are continually migrating outwards, thereby providing space for newly‐divided daughter cells within the more mitotically‐active central region of the hES colony. Secondly, it is proposed that the newly‐divided hES cells within the central region of the colony somehow migrate to the outer periphery. This could possibly explain why the periphery of hES colonies are less mitotically‐active, since there would obviously be an extended time‐lag before newly‐divided daughter cells are ready again for the next cell division. Further investigations need to be carried out to characterize the atypical mechanisms by which hES colonies grow and expand in size. Copyright © 2004 John Wiley & Sons, Ltd.
Large pKa Shifts of α‐Carbon Acids Induced by Copper(II) Complexes
Authors: Zhong Zhenlin , Postnikova Brenda J. , Hanes Robert E. , Lynch Vincent M. , Anslyn Eric V. 
Published: December 2004

AbstractA series of synthetic receptors (4–6) incorporating metal ions, specifically copper(II), were examined for their ability to enhance the acidity of active methylene compounds. The copper(II) complexes were observed to reduce the pKa of 1,3‐diketone carbon acids in acetonitrile by as much as 12 pKa units. The relatively large pKa reduction achieved by the complex is attributed to the electrostatic interaction between the anionic π system of the enolate and the copper(II) ions. The cage structure and hydrogen bonding sites in receptors 4 and 5 lead to a very modest further enhancement of the acidity relative to that with 6. This study provides insight into the way in which metalloenzymes stabilize an enolate intermediate.
Enhanced Stabilization of Reverse Micelles by Compressed CO2
Authors: Shen Dong , Han Buxing , Dong Yu , Wu Weize , Chen Jiawei , Zhang Jiangling 
Published: December 2004

AbstractThe effect of compressed CO2 on the solubilization capacity of water in reverse micelles of sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) in longer chain n‐alkanes was studied at different temperatures and pressures. It was found that the amount of solubilized water is increased considerably by CO2 in a suitable pressure range. The suitable CO2 pressure range in which the solubilization capacity of water could be enhanced decreased with increasing W0 (water‐to‐AOT molar ratio). The microenvironments in the CO2‐stabilized reverse micelles were investigated by UV/Vis adsorption spectroscopy with methyl orange (MO) as probe. The mechanism by which the reverse micelles are stabilized by CO2 is discussed in detail. The main reason is likely to be that CO2 has a much smaller molecular volume than the n‐alkane solvents studied in this work. Therefore, it can penetrate the interfacial film of the reverse micelles and stabilize them by increasing the rigidity of the micellar interface and thus reducing the attractive interaction between the droplets. However, if the CO2 pressure is too high, the solvent strength of the solvents is reduced markedly, and this induces phase separation in the micellar solution.
Löslichkeit von Kohlenwasserstoffen verschiedenen Typs in Methanol und Benzylalkohol
Authors: Sieg Lothar 
Published: December 2004

AbstractIm Laufe von Untersuchungen über die Phasengleichgewichte in ternären und polynären Systemen war es notwendig, die Löslichkeit von Kohlenwasserstoffen in Methyl‐ und Benzylalkohol zu untersuchen. Außer Gesichtspunkten allgemeiner Natur spielte bei dieser Arbeit auch die Erwägung eine Rolle, gegebenenfalls neue analytische und präparative Möglichkeiten zu gewinnen.
Wirbelschicht‐Röstverfahren der Badischen Anilin‐ & Soda‐Fabrik
Authors: Johannsen Adolf 
Published: December 2004

AbstractNachstehend wird über eine neuere Anwendung des Winklerschen Wirbelschicht‐Verfahrens berichtet. Während der Nachkriegsjahre in den Betrieben der Badischen Anilin‐ & Soda‐Fabrik durchgeführte Entwicklungsarbeiten haben ergeben, daß das Wirbelschicht‐Verfahren sehr gut geeignet ist für die Gewinnung hochprozentiger Röstgase durch Abrösten von feinstückigen oder feinkörnigen Schwefelkiesen.
Inhaltsbestimmung teilweise gefüllter Flüssigkeitsbehälter
Authors: Schulze‐Bahr G. 
Published: December 2004

AbstractEs wird der Zusammenhang zwischen dem Höhenverhältnis und dem Füllungsverhältnis für verschiedene Behälterformen, besonders für liegende Zylinder, erörtert und in zwei Nomogrammen dargestellt.
Probleme des konvektiven Stofftransports bei der Elektrolyse
Authors: Ibl N. 
Published: December 2004

AbstractDie Vorgänge des Stofftransports (elektrische Wanderung, Diffusion, Konvektion) führen auch bei der Elektrolyse zu Konzentrationsunterschieden in der Nähe der Elektrodenoberfläche und im Innern der Lösung und bestimmen dadurch die Größe des Grenzstromes, der ein Maß für die maximale Geschwindigkeit ist, mit der ein elektrochemischer Prozeß bei gegebenen Rührbedingungen ausgeführt werden kann. Mit Hilfe der Dimensionsanalyse und der Grenzschichttheorie der Hydrodynamik lassen sich für besonders einfache Fälle diese Daten berechnen bzw. abschätzen, wie an Beispielen gezeigt wird.
Die technische Bedeutung der Abscheidespannung bei der elektrolytischen Gewinnung von Wasserstoff und Sauerstoff
Authors: v. Pichler Alarich 
Published: December 2004

AbstractDie Abscheidespannung, die ein Maß für die bei der Elektrolyse aufgewandte elektrische Arbeit ist, läßt sich durch verschiedene technische und konstruktive Maßnahmen herabsetzen, wie an Beispielen gezeigt wird. Außerdem werden die wärmetechnischen Verhältnisse in der Elektrolysenzelle diskutiert.
Verwertung des bei Chloralkali‐Elektrolysen anfallenden Wasserstoffs zur Ammoniak ‐ Erzeugung
Authors: Hinrichs H. , Niedetzky J. 
Published: December 2004

AbstractDie Österreichischen Stickstoffwerke haben in Schweden eine Anlage errichtet, in der Ammoniak aus dem bei einer Chloralkali‐Elektrolyse anfallenden Wasserstoff gewonnen wird. Bei einer Tageskapazität von 5 bis 15 †; Ammoniak arbeitet die Anlage bisher sehr wirtschaftlich, eine erhebliche Erweiterung wurde bereits ausgeführt.
Verfahrensgrundlagen der Stadt‐ und Ferngasentgiftung
Authors: Gross H. W. 
Published: December 2004

AbstractDie Abhängigkeit des erreichbaren End‐Kohlenoxyd‐Gehaltes von Reaktionstemperatur und Wasserdampfgehalt bei der Konvertierung des Kohlenoxyds mit Wasserdampf wird erläutert. Die optimalen Reaktionsbedingungen lassen sich bei der Gasentgiftung, besonders bei der Behandlung der kohlenoxyd‐reichen Benzin‐ und ölspaltgase nicht immer anwenden, doch wird auch hier mit 3 bis 5% Rest‐Gehalt an Kohlenoxyd noch eine ausreichende Teilentgiftung erzielt. Die Konvertierung von heißen, noch ausreichend Wasserdampf enthaltenden Rohgasen bringt eine erhebliche Kostenersparnis, die durch die Kombination von Konvertierung und Schwefelwasserstoffwäsche in einer Anlage noch vergrößert werden kann.
Neuartiger Redoxtitrations‐Automat
Authors: Boldt Peter , Lackner Helmut 
Published: December 2004

AbstractZur Bestimmung von Redoxpotentialen organischer Verbindungen wurde ein Titrierautomat entwickelt. Dieser unterscheidet sich von den üblichen Titrierautomaten dadurch, daß neue Titrationslösung immer erst dann zugegeben wird, wenn sich das Gleichgewichtspotential sicher eingestellt hat. Dies wird durch einen Abfrage‐Regelvorgang erreicht, der sich periodisch wiederholt, bis die gesamte Titrationskurve aufgezeichnet ist. Die Apparatur arbeitet zuverlässig und ist außerdem billig, gut nachzubauen und leicht zu bedienen.
Erhöhen des Durchsatzes von Extraktionskolonnen durch elektrische Beeinflussung
Authors: Kneule F. , Nemec J. 
Published: December 2004

AbstractDurch Einwirken elektrischer Felder läßt sich die Trennzeit stabiler Emulsionen verkürzen und somit die Raum‐Zeit‐Ausbeute von Extraktionsanlagen erhöhen. Die Anwendungsmöglichkeiten des Verfahrens beschränken sich auf Phasensysteme, bei denen die in einem flüssigen Dielektrikum dispergierte Phase elektrisch leitend ist.
Fortschritte auf dem Gebiet der Elektronenmikroskopie. Bericht über die 11. Tagung der Deutschen Gesellschaft für Elektronenmikroskopie
Authors: Speidel R. 
Published: December 2004

AbstractDie 11. Tagung der Deutschen Gesellschaft für Elektronenmikroskopie wurde dieses Jahr gemeinsam mit der Sektion Elektronen‐Optik und Mikroskopie des Schweizerischen Komitees für Optik vom 22. bis 26. September in Zürich abgehalten. In den vier Tagen wurde eine Fülle physikalischer Probleme und Ergebnisse diskutiert. Dieser Bericht beschränkt sich jedoch auf die Entwicklung der Geräte und Präparationstechniken, die für den Techniker und Anwender der Elektronenmikroskopie von Bedeutung sind.
Zur Theorie der Elektroosmose
Authors: Schmid Gerhard 
Published: December 2004

AbstractDie klassische Theorie der Elektroosmose von Helmholtz und v. Smoluchowski, die aus der Vorstellung einer elektrischen Doppelschicht an der inneren Phasengrenze der Porenwandungen abgeleitet ist, versagt bei der Anwendung auf Membranen. Die neue Theorie betrachtet vielmehr die feinporigen Kapillarsysteme der Membranen in erster Näherung als homogene Elektrolyte, in denen sich teils bewegliche (austauschbare), teils unbewegliche (an die Matrix der Membran gebundene) Ionen befinden. Man wird dadurch unabhängig von der Annahme einer bestimmten Porenstruktur der Membran und gewinnt Ansätze, die auch die elektrische Leitfähigkeit und das Dialysepotential mit den elektroosmotischen Erscheinungen in Zusammenhang bringen.
Mikromanometer hoher Empfindlichkeit
Authors: Elgeti K. , Eckert E. R. G. 
Published: December 2004

AbstractZum Ausmessen von Geschwindigkeitsfeldern in laminarer Strömung von Gasen wurde ein empfindliches Mikromanometer entwickelt, das eine Meßgenauigkeit von 3 · 10−5 mmWS oder — bei größeren Druckdifferenzen — von 0,5% hat. Der Meßbereich beträgt etwa 2,5 mmWS. Das Gerät arbeitet nach dem U‐Rohr‐Prinzip mit elektrischer Anzeige der Flüssigkeitshöhe. Es liefert Gleichspannung, und zwar bei der verwendeten Manometerflüssigkeit etwa 0,51 V je mm WS Druckdifferenz.