bluuebunny/crossref_metadata_2025_split huggingface dataset:
A structured metabolic model for anaerobic and aerobic stoichiometry and kinetics of the biological phosphorus removal process
Authors: Smolders G. J. F. , van der Meij J. , van Loosdrecht M. C. M. , Heijnen J. J. 
Published: December 2004

AbstractA structured metabolic model is developed that describes the stoichiometry and kinetics of the biological P removal process. In this approach all relevant metabolic reactions underlying the metabolism, considering also components like adenosine triphosphate (ATP) and nic‐otinamide‐adenine dinucleotide (NADH2) are describedbased on biochemical pathways. As a consequence of the relations between the stoichiometry of the metabolic reactions and the reaction rates of components, the required number of kinetic relations to describe the process is reduced. The model describes the dynamics of the storage compounds which are considered separately from the active biomass. The model was validated in experiments at a constant sludge retention time of 8 days, over the anaerobic and aerobic phases in which the external oncentrations as well as the internal fractions of the relevant components involved in the P‐removal process were monitored. These measurements include dissolved acetate, phosphate, and ammonium; oxygen consumption; poly‐β‐hydroxybutyrate (PHB); glycogen; and active biomass. The model satisfactorily describes the dynamic behavior of all components during the anaerobicand aerobic phases.© 1995 John Wiley & Sons, Inc
In‐situ removal of ammonium and lactate through electrical means for hybridoma cultures
Authors: Chang Yu‐Hsiang David , Grodzinsky Alan J. , Wang Daniel I. C. 
Published: December 2004

AbstractAmmonium and lactate are two known toxic products detrimental to mammalian cell growth and productivity. An electrokinetic technique, utilizing an electrophoretic mechanism, was developed to remove these cellular wastes in‐situ from suspension hybridoma (ATCC CRL‐1606) cultures to enhance cell growth and productivity. This technique applies continuously a dc electric field to selectively remove the electrically charged wastes. The experiments were shown to be successful in the removal of externally added 10 rnM ammonium and 45 mM lactate while maintaining the chemostatic condition of culture medium in a cell‐free condition under an electric current density of 50 A/m2. Toxic levels of ammonium were added, ranging from 7.5 to 12.5 mM, at the start of the hybridoma culture, and the applied dc electric fields were able to completely remove these added materials. This in turn released the inhibition and restored the cell growth. Finally, this electrokinetic technique was applied to the batch and glutamine fed‐batch hybridoma cultures. At an applied electric current density of 50 A/m2, this was able to completely remove cell‐produced ammonium and increased the cell growth and antibody titer by 30% to 50%, respectively, compared to the control experiment in the absence of the electric field. Lastly, the applied electric current density of 50 A/m2 did not affect cellular functionalities such as glucose and glutamine consumption and antibody productivity.© 1995 John Wiley & Sons, Inc
Analysis of cell‐to‐bubble attachment in sparged bioreactors in the presence of cell‐protecting additives
Authors: Michaels James D. , Nowak Jason E. , Mallik Ameet K. , Koczo Kalman , Wasan Darsh T. , Papoutsakis Eleftherios T. 
Published: December 2004

AbstractTo investigate the mechanisms of cell protection provided by medium additives against animal cell injury in sparged bioreactors, we have analyzed the effect of various additives on the cell‐to‐bubble attachment process using CHO cells in suspension. Cell‐to‐bubble attachment was examined using three experimental techniques: (1) cell‐bubble induction time analysis (cell‐to‐bubble attachment times); (2) forming thin liquid films and observing the movement and location of cells in the thin films; and (3) foam flotation experiments. The induction times we measured for the various additives are as follows: no additive (50 to 500 ms), polyvinyl pyrrolidone (PVP: 20 to 500 ms), polyethylene glycol (PEG: 200 to 1000 ms), 3% serum (500 to 1000 ms), polyvinyl alcohol (PVA: 2 to 10 s), Pluronic F68 (5 to 20 s), and Methocel (20 to 60 s). In the thin film formation experiments, cells in medium with either F68, PVA, or Methocel quickly flowed out of draining thin liquid films and entered the plateau border. When using media with no additive or with serum, the flow of cells out of the thin liquid film and film drainage were slower than for media containing Pluronic F68. PVA, or Methocel. With PVP and PEG, the thin film drainage was much slower and cells remained trapped in the film. For the foam flotation experiments, a separation factor (ratio of cell concentration in the foam catch to that in the bubble column) was determined for the various additives. In the order of increasing separation factors (i.e., increasing cell attachment to bubbles), the additives are as follows: Methocel, PVA, Pluronic F68, 3% serum, serum‐free medium with no additives, PEG, and PVP. Based on the results of these three different cell‐to‐bubble attachment experiments, we have classified the cell‐protecting additives into three groups: (1) Pluronic F68, PVA, and Methocel (reduced cell‐to‐bubble attachment); (2) PEG and PVP (high or increased cell‐to‐bubble attachment); and (3) FBS (reduced cell attachment butslower drainage films compared with F68, PVA, and Methocel with some cell entrapment in those films). These phenomena are discussed in relation to the interfacial properties of the media reported in a companion Study (this issue). © 1995 John Wiley & Sons Inc.
Enhanced acetone‐butanol fermentation using repeated fed‐batch operation coupled with cell recycle by membrane and simultaneous removal of inhibitory products by adsorption
Authors: Yang Xiaoping , Tsao George T. 
Published: December 2004

AbstractA novel acetone–butanol production process was developed which integrates a repeated fed‐batch fermentation with continuous product removal and cell recycle. The inhibitory product concentrations of the fermentation by Clostridium acetobutylicum were reduced by the simultaneous extraction process using polyvinylpyridine (PVP) as an adsorbent. Because of the reduced inhibition effect, a higher specific cell growth rate and thus a higher product formation rate was achieved. The cell recycle using membrane separation increased the total cell mass density and, therefore, enhanced the reactor productivity. The repeated fed‐batchoperation overcame the drawbacks typically associated with a batch operation such as down times, long lag period, and the limitation on the maximum initial substrate concentration allowed due to the substrate inhibition. Unlike a continuous operation, the repeated fed‐batch operation could beoperated for a long time at a relatively higher substrate concentration without sacrificing the substrate loss in the effluent. As a result, the integrated process reached 47.2 g/L in the equivalent solvent concentration (including acetone, butanol, and ethanol) and 1.69 g/L · h in the fermentor productivity, on average, over a 239.5‐h period. Compared with a controlled traditional batch acetone–butanol fermentation, the equivalent solvent concentration and the tormentor productivity were increased by 140% and 320%, respectively. © 1995 John Wiley & Sons Inc.
Morphology of Trichoderma reesei QM 9414 in submerged cultures
Authors: Lejeune R. , Nielsen J. , Baron G. V. 
Published: December 2004

AbstractThe microscopic morphology of Trichoderma reesei QM 9414, growing in submerged culture, was studied by image analysis. The morphology was characterized by the total hyphal length, the total number of tips, the number of actively growing tips, and the length of the main hypha. To describe the growth of a single mycelium a simple model is set‐up. The main features of the model are: (1) saturation type kinetics for the tip extension of the individual branches within the mycelium; and (2) random branching with a frequency function, which is proportional to the total hyphal length. The model is used to simulate a population of mycelia, where spore germination is described with a log‐normal distribution. From the simulation of the population, the average properties of the mycelia, e.g., the average total hyphal length, are calculated, and by fitting the model to experimental data the model parameters are estimated. Finally, the distribution function with respect to the mycelia properties, that is, number of tips and total hyphal length, is calculated, and it corresponds well with the experimental determination of the distribution function. © 1995 John Wiley & Sons Inc.
Sequential adsorption of F(ab′)2 and BSA on negatively and positively charged polystyrene latexes
Authors: Ortega‐Vinuesa J. L. , Hidalgo‐Álvarez R. 
Published: December 2004

AbstractThe aim of the present work is to study the sequential adsorption of F(ab′)2 and bovine serum albumin (BSA) molecules adsorbed onto positively and negatively charged polystyrene latexes. Cationic and anionic latexes were prepared by emulsifier‐free emulsion polymerization. Adsorptions of F(ab′)2 on both latexes at a low ionic strength and different pHs were performed. The cationic latex showed a higher adsorption of F (ab′)2 molecules over a range of pH, which could be due to the formation of multilayers. Sequential adsorption of anti‐CRP F(ab′)2 and monomeric BSA were performed at two different pre‐adsorbed F(ab′)2 amounts on both types of latex. Displacement of F(ab′)2 occurred only when the preadsorbed amounts were larger than a certain critical value, which depends on the adsorption pH. A greater displacement of larger preadsorbed amounts might be the result of a weaker contact between the protein molecules and the polystyrene surface. The displacement of F(ab′)2 previously adsorbed onto both latexes occurred due to pH changes, an increase of ionic strength and the presence of BSA molecules. The effect caused by these three factors was studied independently. The main factors in the desorption of F(ab′)2 on the anionic latex are the changes in pH and ionic strength, whereas on the cationic latex the desorption is mainly caused by the increase of the ionic strength and the presence of BSA. The colloidal stability of the immunotatex was improved by BSA adsorption, especially on cationic latex. © 1995 John Wiley & Sons, Inc.
On the use of the pH control reagent addition rate for fermentation monitoring
Authors: Siano Steven A. 
Published: December 2004

AbstractThe linear relation between the pH control reagent addition rate, the net conversion rates of metabolites, the carbon dioxide mass transfer rate and the feed rates is developed and shown to have the same form for batch, fed‐batch, and continuous reactors, regardless of the number of feeds. The magnitudes of various biological and solution chemistry effects on the pH control reagent addition rate are estimated to be negligible, facilitating the use of the pH control reagent addition rate as a straightforward indicator of primary metabolism. Finally, application of the linear relation, termed the abiotic proton balance, is discussed for a number of fermentation processes. © 1995 John Wiley & Sons, Inc.
Use of comparative reasoning tools for evaluation of the effect of sterilization conditions on fermentations to produce acidic fibroblast growth factor
Authors: Marshall Carolynne T. , Lilly Malcolm D. , Gbewonyo Kodzo , Buckland Barry C. 
Published: December 2004

AbstractThe effects of various medium sterilization conditions on fermentations of a recombinant, acidic fibroblast growth factor (aFGF) producing Escherichia coli have been studied. Changes in the medium resulting from sterilization were monitored by pH and absorption spectra. This simple experiment provided excellent data for the demonstration of the usefulness of comparative reasoning tools in order to evaluate the effect of sterilization on fermentation performance. The time profiles of the main parameters (e.g., carbon dioxide evolution rate, dissolved oxygen, pH, and aFGF productivity) were simplified into piecewise contiguous linear segments, each of which was sequentially numbered. The length, position, and slope of each tine were then characterized. Application of the comparative reasoning tools confirmed that separate sterilization of the glucose was necessary for the success of the process, despite adding to the cost and complexity. The comparative data analysis also showed that scaleup with longer sterilization holding and cooling times would not be detrimental to aFGF production. © 1995 John Wiley & Sons, Inc.
Modeling biofilm accumulation and mass transport in a porous medium under high substrate loading
Authors: Wanner O. , Cunningham A. B. , Lundman R. 
Published: December 2004

AbstractA packed bed biofilm reactor inoculated with pure culture Pseudomonas aeruginosa was run under high substrate loading and constant flow rate conditions. The 3.1‐cm‐diameter cylindrical reactor was 5 cm in length and packed with 1‐mm glass beads. Daily observations of biofilm thickness, influent and effluent glucose substrate concentration, and effluent dissolved and total organic carbon were made during the 13‐day experiment. Biofilm thickness appeared to rech quasi‐steady‐state condition after 10 days. A published biofilm process simulation program (AQUASIM) was used to analyze experimental data. Comparison of observed and simulated variables revealed three distinct phases of biofilm accumulation during the experiment: an initial phase, a growth phase, and a mature biofilm phase. Different combinations of biofilm and mass transport process variables were found to be important during each phase. Biofilm detachment was highly correlated with shear at the biofilm surface during all three phases of biofilm development. © 1995 John Wiley & Sons, Inc.
Implantable hollow fiber bioreactor as a potential treatment for hypercholesterolemia: Characterization of the catalytic unit
Authors: Shefer Samuel D. , Rosenberger Vered , Vahanian Gizette , Wong Wai T. , Langer Robert 
Published: December 2004

AbstractPrevious studies have shown that the modification of low density lipoprotein (LDL) by the enzyme phospholipase A2(PLA2)results in a reduction of cholesterol levels in the plasma of hypercholesterolemic rabbits, due to accelerated clearance of the modified LDL. In the current study, we established techniques and optimized the ratio of enzyme to support for the immobilization of PLA2 on a polymeric support. Hollow fiber bioreactors made from polytetrafluoroethylene (PTFE) polymers were used to encapsulate immobilized PLA2. This design was adopted to eliminate hemolysis of red blood cells by the enzyme. Characterization of the resulting immobilized enzyme in terms of its activity, Michaelis‐Menten kinetic constants, and the variation of its activity with incubation time is presented. The enzyme activity was not significantly altered upon incubation at 37°C in lipoprotein‐deficient serum (LPDS), over the course of 2 months. The Michaelis–Menten kinetics constants are KM = 8.9 mM, Vmax = 6434.2 for the free enzyme and K = 16.7 mM, V = 619.7 for the immobilized enzyme. These data suggest that a system based on immobilized PLA2 in conjunction with hollow fiber bioreactors (HFBs) may be a good candidate for lowering LDL levels in plasma. © 1995 John Wiley & Sons, Inc.
Overexpression of bcl‐2, apoptosis suppressing gene: Prolonged viable culture period of hybridoma and enhanced antibody production
Authors: Itoh Yohito , Ueda Hiroshi , Suzuki Eiji 
Published: December 2004

AbstractHuman bcl‐2 DNA was introduced into mouse hybridoma 2E3 cells and expressed at a high level by using BCMGSneo vector, which reportedly amplifies as multiple copies in the cells independently of their chromosomes. The high expression of bcl‐2 in BCMGSneo‐bcl‐2 transfectants was confirmed by western blotting. In batch cultures, the overexpression of bcl‐2 raised the maximum viable cell density by 45%, delayed the initiation of apoptosis by 2 days, and prolonged the viable culture period by 4 days. The delayed initiation of apoptosis was detected by emergence of the ladder pattern on DNA electrophoresis and increase of the dead cell number. The bcl‐2 transfectants produced lgG1 fourfold per batch culture in comparison with 2E3 cells transfected with BCMGSneo but not with bcl‐2: a little less than twofold due to the improved survival of the cells and more than twofold due to the enhanced lgG1 production rate per cell of the bcl‐2 transfectants. The method to engineer hybridoma cells genetically with bcl‐2 using BCMGSneo vector for increasing viability and productivity would be widely applied for improving antibody productivity of hybridoma cultures. © 1995 John Wiley & Sons, Inc.
Augmentation of mass transfer through electrical means for hydrogel‐entrapped Escherichia coli cultivation
Authors: Chang Yu‐Hsiang David , Grodzinsky Alan J. , Wang Daniel I. C. 
Published: December 2004

AbstractNutrient depletion and inhibitory end‐product accumulation are the major problems for hydrogel‐entrapment cell cultures. An electrokinetic technique was developed to enhance intrahydrogel mass transfer to overcome these problems. Escherichia coli cells (ATCC 15224) were entrapped in 3.2‐mm‐thick potassium‐K‐carrageenan and agarose hydrogel slabs. With a electric current density of 180A/m2 the cell densities were increased by 140%(from 3.9 to 9.6 dry cell weight [DCW] g/L) in potassium‐K‐carrageenan and by 80% (from 3.9 to 7.0 DCW g/L) in agarose. A mathematical model taking into account nutrient depletion, inhibitory end‐product formation, and cell growth kinetics under facultatively anaerobic conditions was developed to rationalize the overall transport and biological behaviors in the hydrogel. The cell growth in hydrogel was successfully simulated. It is concluded that the augmented transports for glucose and inhibitory end‐products accounted for these increases in cell growth. The increase in cell density in potassium‐K‐carrageenan was due to the enhanced removal of inhibitory end‐products (through electroosmosis and electro‐phoresis: 80%) and due to the augmented glucose transport (through electroosmosis: 20%). © 1995 John Wiley & Sons, Inc.
Effects of chemical treatments and heating on the crystallinity of celluloses and their implications for evaluating the effect of crystallinity on cellulose biodegradation
Authors: Weimer P. J. , Hackney J. M. , French A. D. 
Published: December 2004

AbstractChemical treatments similar to those routinely used to extract cellulose from plant biomass caused significant increases in the relative crystallinity index (RCI) of Sig‐macell 100 (a commercial cellulose of moderate crystallinity), as measured by x‐ray powder diffraction in both the reflectance and transmittance modes. In general, the largest increases in RCI were observed following higher (rather than lower) temperature treatments. Substantial increases in crystalliity were also observed upon resuspension in water prior to drying, with higher temperatures again resulting in the greatest increases in RCI. Measurement of the RCIs of wetted Sigmacell 100 samples by acid hydrolysis kinetics revealed that most of the increased crystallinity occurred rapidly upon contact with water. In contrast to Sigmacell 100, a cellulose of higher initial crystallinity (the microcrystalline cellulose Sigmacell 50) showed little change in crystallinity following the above treatments. The results provide a partial explanation for the inconsistent relationships reported between cellulose crystallinity and cellulose biodegradation. © 1995 John Wiley & Sons, Inc.
Protein purification by bulk crystallization: The recovery of ovalbumin
Authors: Judge Russell A. , Johns Michael R. , White Edward T. 
Published: December 2004

AbstractCrystallization is used industrially for the recovery and purification of many inorganic and organic materials. However, very little is reported on the application of bulk crystallization for proteins. In this work, ovalbumin was selected as a model protein to investigate the feasibility of using bulk crystallization for the recovery and purification of proteins. A stirred 1‐L seeded batch crystallizer was used to obtain the crystal growth kinetics of ovalbumin in ammonium sulfate solutions at 30°C. The width of the metastable region, in which crystal growth can occur without any nucleation, is equivalent to a relative supersaturation of about 20. The bulk crystallizations were undertaken within this range (using initial relative supersaturations less than 10) and nucleation was not observed. The ovalbumin concentration in solution was measured by UV absorbance and checked by crystal content measurement. Crystal size distributions were measured both by using a Malvern Mastersizer and by counting crystals through a microscope. The crystal growth rate was found to have a second‐order dependence upon the ovalbumin supersaturation. While there is no discernible effect of ammonium sulfate concentration at pH 4.90, there is a slight effect at higher pH values. Overall the effect of ammonium sulfate concentration is small compared to the effect of pH, for which there is a 10‐fold increase in the growth rate constant, kGσ over the range pH 4.6–5.4. To demonstrate the degree of purification which can be achieved by bulk crystallization, ovalbumin was crystallized from a solution containing conalbumin (80,000 Da) and lysozyme (14, 600 Da). After one crystallization and a crystal wash, ovalbumin crystals were produced with a protein purity greater than 99%. No contamination by the other proteins was observed when using overloaded sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) stained with Coomassie blue stain and only trace amounts of lysozyme were observed using a silver stain. The presence of these other proteins in solution did not effect the crystal growth rate constant, kGσ. The study demonstrates the feasibility of using bulk crystallization for the recovery and purification of ovalbumin. It should be readily applicable to other protein systems. © 1995 John Wiley & Sons, Inc.
Development of an expanded bed technique for an affinity purification of G6PDH from unclarified yeast cell homogenates
Authors: Chang Y. K. , McCreath G. E. , Chaset H. A. 
Published: December 2004

AbstractThe use of an expanded bed of STREAMLINE Red H‐7B for the purification of the intracellular glycolytic enzyme glucose 6‐phosphate dehydrogenase (G6PDH) directly from untreated preparations of disrupted yeast cells has been investigated. Small‐scale experiments, carried out in packed beds, have shown that the optimal pH for adsorption is 6.0 and have enabled optimization of elution conditions using a series of eluents. The dynamic capacity of the adsorbent for G6PDH was determined in a small expanded bed to be 28 units/mL. These results were used to develop a preparative scale separation of G6PDH in a STREAMLINE 50 expanded bed column. G6PDH was purified directly from an unclarified yeast homogenate in 99% yield with an average purification factor in the eluted fraction of 103. Cleaning‐in‐place (CIP) procedures using 0.5 M NaOH and 4M urea in 60% (v/v) ethanol have demonstrated that the adsorbent can be regenerated with no loss of adsorption capacity of alteration of bed expansion characteristics after many cycles of operation. © 1995 John Wiley & Sons, Inc.