bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions between animal cells and gas bubbles: The influence of serum and pluronic F68 on the physical properties of the bubble surface
Authors: Jordan M. , Eppenberger H. M. , Sucker H. , Widmer F. , Einsele A. 
Published: December 2004

AbstractWe describe a method by which the degree of bubble saturation can be determined by measuring the velocity of single bubbles at different heights from the bubble source in pure water containing increasing concentrations of surfactants. The highest rising velocities were measured in pure water. Addition of surfactants caused a concentration‐dependent and height‐dependent decrease in bubble velocity; thus, bubbles are covered with surfactants as they rise, and the distance traveled until saturation is reached decreases with increased concentration of surfactant. Pluronic F68 is a potent effector of bubble saturation, 500 times more active than serum. At Pluronic F68 concentrations of 0.1% (w/v), bubbles are saturated essentially at their source. The effect of bubble saturation on the interactions between animal cells and gas bubbles was investigated by using light microscopy and a micromanipulator. In the absence of surfactants, bubbles had a killing effect on cells; hybridoma cells and Chinese hamster ovary (CHO) cells were ruptured when coming into contact with a bubble. Bubbles only partially covered by surfactants adsorbed the cells. The adsorbed cells were not damaged and they also could survive subsequent detachment. Saturated bubbles, on the other hand, did not show any interactions with cells. It is concluded that the protective effect of serum and Pluronic F68 in sparged cultivation systems is based on covering the medium–bubble interface with surfaceactive components and that cell death occurs either after contact of cells with an uncovered bubble or by adsorption of cells through partially saturated bubbles and subsequent transport of cells into the foam region. © 1994 John Wiley & Sons, Inc.
Model of the anaerobic metabolism of the biological phosphorus removal process: Stoichiometry and pH influence
Authors: Smolders G. J. F. , van der Meij J. , van Loosdrecht M. C. M. , Heijnen J. J. 
Published: December 2004

AbstractIn the anaerobic phase of a biological phosphorus removal process, acetate is taken up and converted to PHB utilizing both energy generated in the degradation of polyphosphate to phosphate, which is released, and energy generated in the conversion of glycogen to poly‐β‐hydroxy butyrate (PHB). The phosphate/acetate ratio cannot be considered a metabolic constant, because the energy requirement for the uptake of acetate is strongly influenced by the pH value. The observed phosphate/acetate ratio shows a variation of 0.25 to 0.75 P‐mol/C‐mol in a pH range of 5.5 to 8.5. It is shown that stored glycogen takes part in the metabolism to provide reduction equivalents and energy for the conversion of acetate to PHB. A structured metabolic model, based on glycogen as the source of the reduction equivalents in the anaerobic phase and the effect of the pH on the energy requirement of the uptake of acetate, is developed. The model explains the experimental results satisfactorily. © 1994 John Wiley & Sons, Inc.
Studies on microbial chromate reduction by Pseudomonas Sp. In aerobic continuous suspended growth cultures
Authors: Gopalan R. , Veeramani H. 
Published: December 2004

AbstractReduction of hexavalent chromium was studied in three bench‐scale continuous stirred tank reactors. The inoculum was a culture of Pseudomonas sp., capable of giving 83% to 87% chromate reduction in 72‐h batch assays with 60 mg Cr(VI) L−1 in synthetic medium. The continuous culture studies were conducted for about 100 days using synthetic feed containing different levels of chromate (5 to 124 mg L−1) at 28° to 30°C and pH 6.8. The feed rate was varied over the range 0.5 to 1 L d−1 to obtain hydraulic retention time of 36 to 72 h. Chromate reduction efficiency was 81% to 91% and 100% for influent Cr(VI) concentrations of 15 to 124 and 5 mg L−1, respectively, with a hydraulic retention time of 72 h. © 1994 John Wiley & Sons, Inc.
Cadmium removal in a biosorption column
Authors: Volesky B. , Prasetyo I. 
Published: December 2004

AbstractNew biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed‐bed flow‐through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent, representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N0) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L. The critical bed depth (Dmin) for the potable water effluent quality standard (0.005 mgg Cd/L) varied with the column feed flow rate (2.4 to 9.6 L/h · cm2) from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations. © 1994 John Wiley & Sons, Inc.
Enzymatic synthesis of alkyl β‐D‐xylosides by transxylosylation and reverse hydrolysis
Authors: Drouet Philippe , Zhang Mu , Legoy Marie Dominique 
Published: December 2004

AbstractTheTrichoderma reeseiβ‐xylosidase (EC 3.2.1.37) is used to catalyze the production of alkyl β‐D‐xyloside. Two general methods of production are tested and compared using the same enzyme: transglycosylation and reverse hydrolysis. Using both methods, primary, secondary, and tertiary alcohols are studied as acceptors. In kinetically controlled process (transglycosylation), the chosen donor is methyl β‐D‐xyloside and primary, secondary, and tertiary alkyl alcohols are accepted. In the equilibrium‐controlled synthesis, the donor is xylose whereas acceptors are only primary and secondary alcohols. The influence of the donor concentration is investigated in both processes. The yields of the kinetically controlled reactions are higher compared with those of the equilibrium‐controlled synthesis. The specificity of the β linkage is confirmed by proton nuclear magnetic resonance (1H NMR) analysis. © 1994 John Wiley & Sons, Inc.
Communication to the editor. Application of the cross‐regulation system as a metabolic switch
Authors: Chen Wilfred , Bailey James E. 
Published: December 2004

AbstractThe ability to switch metabolic flow from one pathway to another at a desired point in a bioprocess expands the horizons of metabolic engineering. Such an externally inducible switch can be realized by embedding synthetic operons behind tow corss‐regulated promoters. This results in coordinated cessation of transcription of one operon while transcription of a second operon is simultaneously activated. The ability to effect such coordinated and inverse control of transcription of two operons has been illustrated experimentally using a model construct containing two different reporter genes, Vitreoscilla hemoglobin (VHb) and chloramphenicol acetyltransferase (CAT), fused to λPL and tac promoters, respectively, along with corresponding repressor genes in a cross‐regulation configuration. Only VHb production was observed preinduction, and postinduction only CAT was produced. The framework presented here and its obvious extensions can be used with different combinations of promoter systems and synthetic operon constructs to achieve complicated metabolic flux regulation in diverse host. © 1994 John Wiley & Sons, Inc.
Development and application of thermo‐sensitive immunomicrospheres for antibody purification
Authors: Kondo Akihiko , Kaneko Tetsuya , Higashitani Ko 
Published: December 2004

AbstractThe latex particles composed of poly(styrene/N‐isopropylacrylamide/glycidyl methacrylate) [P(St/NIPAM/GMA)] and poly(styrene/N‐isopropylacrylamide/methacrylic acid) [P(St/NIPAM/MAA)] were prepared by emulsifier‐free emulsion polymerization. These latex particles with submicrometer size showed the thermosensitivity originated from the thermo‐sensitive nature of NIPAM. That is, the minimum NaCI concentration for flocculation of these latex particles [critical flocculation concentration (CFC)] decreased significantly with increasing temperature and reached constant values at above the critical temperature [critical flocculation temperature (CFT)]. At a certain NaCl concentration, the thermo‐sensitive latex particles were flocculated by raising temperature, and conversely, the flocculated thermo‐sensitive latex particles were completely dispersed by lowering temperature. Bovine serum albumin (BSA) was covalently immobilized onto the P(St/NIPAM/GMA) and P(St/NIPAM/MMA) latex particles with high efficiency. The BSA‐immobilized P(St/NIPAM/GMA) and P(St/NIPAM/MAA) latex particles (immunomicrospheres) showed the similar dependencies of CFC on temperature to the bare latex particles. These thermo‐sensitive immunomicrospheres were successfully used for the immunoaffinity purification of anti‐BSA antibodies from antiserum. © 1994 John Wiley & Sons, Inc.
Genetically engineered charge modifications to enhance protein separation in aqueous two‐phase systems: Electrochemical partitioning
Authors: Luther John R. , Glatz Charles E. 
Published: December 2004

AbstractWe have examined the effect of genetically engineered charge modifications on the partitioning behavior of proteins in dextran/polyethylene glycol two‐phase systems containing potassium phosphate. By genetically altering a protein's charge, the role of charge on partitioning can be assessed directly without the need to modify the phase system. The charge modifications used are of two types: Charged tails of polyaspartic acid fused to β‐galactosidase and charge‐change point mutations of T4 lysozyme which replace positive lysine residues with negative glutamic acids. The partition coefficient Kp for these proteins was related to measured interfacial potential differences Δϕ using the simple thermodynamic model, In Kp = In Ko + (F/RT)Zp δϕ. The protein net charge Zp was determined using the Henderson–Hasselbalch relationship with modifications based on experimentally determined titration and isoelectric point data. It was found that when the electropartitioning term Zp δϕ was varied by changing the pH, the partitioning of T4 lysozyme was quantitatively described by the thermodynamic model. The β‐galactosidase fusions displayed qualitative agreement, and although less than predicted, the partitioning increased more than two orders of magnitude for the pH range examined. Changes in the partitioning of lysozyme due to the various mutations agreed qualitatively with the thermodynamic model, but with a smaller than expected dependence on the estimated charge differences. The β‐galactosidase fusions, on the other hand, did not display a consistent charge based trend, which is likely due either to the enzyme's large size and complexity or to nonelectrostatic contributions from the tails. The lack of quantitative fit with the model described above suggests that the assumptions made in developing this model are oversimplified. © 1994 John Wiley & Sons, Inc.
Microfiltration of streptococcal fermentation broths: Study of the factors affecting the concentration effect
Authors: Hernandez‐Pinzon Immaculada , Bautista Juan 
Published: December 2004

AbstractStreptokinase (SK) recovery from streptococcal fermentation broth by cross‐flow microfiltration has been studied. Recovery of SK in the filtrate, independent of the volumetric concentration factor, is approximately two‐fold lower than the initial SK activity in the fermentation broth; moreover, the SK activity in the retentate increase during the process, reaching a concentration factor of 2.73. These results show that the membrane works more as an ultrafiltration membrane, with rejection of S = 0.6, than as a microfiltration membrane. Under filtration conditions, the membrane permeation rate decreased with time. This decreased could be explained by deposition and interaction of material onto/with the membrane resulting in the concentration of permeable products. Studies of the individual concentration factors for the main streptococcal exocellular proteins, indicate clearly that the concentration of the proteins during the microfiltration process is independent of the size of the proteins, suggesting that other factors, such as charge and hydrophobicity, along with concentration‐polarization, should be taken also into account for the understanding of this phenomenon. © 1994 John Wiley & Sons, Inc.
Chemical and enzymatic extraction of heavy metal binding polymers from isolated cell walls of Saccharomyces cerevisiae
Authors: Brady D. , Stoll A. D. , Starke L. , Duncan J. R. 
Published: December 2004

AbstractIsolated cell walls of the yeast Saccharomyces cerevisiae were treated by either chemical (alkali and acid) or enzymatic (protease, mannanase or β‐glucuronidase) processes to yield partially purified products. These products were partially characterized by infrared analysis. They were subsequently reacted with heavy metal cation solutions and the quantity of metal accumulated by the cell wall material determined. The Cu2+ ion (0.24, 0.36, 1.12, and 0.60 μmol/mg) was accumulated to a greater extent than either Co2+ (0.13, 0.32, 0.43, and 0.32 μmol/mg) or Cd2+ (0.17, 0.34, 0.39, and 0.32 μmol/mg) by yeast cell walls, glucan, mannan, and chitin, respectively The isolated components each accumulated greater quantities of the cations than the intact cell wall. Removal of the protein component of the yeast cell walls by Pronase caused a 29.5% decrease in metal accumulation by yeast cell walls per mass, indicating the protein is a heavy metal accumulating component. The data indicate that the outer mannan–protein layer of the yeast cell wall is more important than the inner glucan‐chitin layer in heavy metal action accumulation. © 1994 John Wiley & Sons, Inc.
Modification of islet of langerhans surfaces with immunoprotective poly(ethylene glycol) coatings via interfacial photopolymerization
Authors: Sawhney Amarpreet S. , Pathak Chandrashekhar P. , Hubbell Jeffrey A. 
Published: December 2004

AbstractPoly(ethylene glycol) (PEG) has been used previously to alter immune interactions and systemic clearance of therapeutic proteins. We present herein chemical approaches for the conceptually similar treatment of therapeutic cells and tissues whereby immune and cell adhesive interactions may be reduced or interrupted, in the context of the transplantation of xenogeneic islets of Langerhans for the treatment of insulin‐dependent diabetes mellitus. Visible‐light‐initiated interfacial photopolymerization of multifunctional PEG‐based macromers was performed directly upon the surface of rat islets of Langerhans to produce conformal barrier hydrogel coatings with thickness of order 10 μ;m. The islets continued to be normal in ultrastructure and function as reflected by response to a glucose challenge in vitro. © 1994 John Wiley & Sons, Inc.
Effects of water activity on reaction rates and equilibrium positions in enzymatic esterifications
Authors: Svensson Ingemar , Wehtje Ernst , Adlercreutz Patrick , Mattiasson Bo 
Published: December 2004

AbstractA technique of continuous water activity control was used to examine the effects of water activity on enzyme catalysis in organic media. Esterification catalyzed by Rhizopus arrhizus lipase was preferably carried out at a water activity of 0.33, which resulted in both maximal initial reaction rate and a high yield. When Pseudomonas lipase was used as catalyst it was beneficial to start the reaction at high water activity (giving the optimal reaction rate with this enzyme) and then shift to a lower water activity toward the end of the reaction to obtain a high yield. The apparent equilibrium constant of the reaction was influenced by the water activity of the organic solvent. © 1994 John Wiley & Sons, Inc.
Formation and growth of heterotrophic aerobic biofilms on small suspended particles in airlift reactors
Authors: Tijhuis L. , van Loosdrecht M. C. M. , Heijnen J. J. 
Published: December 2004

AbstractIn this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start‐up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start‐up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start‐up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt‐maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 ± 0.08 C‐mol/C‐mol, the maintenance value 0.019 ± 0.012 C‐mol/(C‐mol h). The lowest actual biomass yield measured in this study was 0.15 C‐mol/C‐mol. © 1994 John Wiley & Sons, Inc.
The release of virus‐like particles from recombinant Saccharomyces cerevisiae: Effect of freezing and thawing on homogenization and bead milling
Authors: Milburn P. T. , Dunnill P. 
Published: December 2004

AbstractRecombinant cells of Saccharomyces cerevisiae, expressing virus‐like particles (Ty‐VLPs), can be readily disrupted in a high pressure homogenizer and show identical disruption kinetics to the untransformed host strain. When the cells are freeze/thawed before disruption, they become about four times more resistant to homogenization. This effect increases with the number of freeze/thaw cycles, but is independent of the time the cells remain frozen. The freeze/thaw effect is observed with cells harvested during both the logarithmic and stationary phase of growth, and occurs with the untransformed host strain as well as the transformed one. Freeze/thawed cells are twice as resistant to disruption in the bead mill as fresh cells. © 1994 John Wiley & Sons, Inc.
Recovery of proteins and amino acids from reverse micelles by dehydration with molecular sieves
Authors: Gupta Ram B. , Han Chae J. , Johnston Keith P. 
Published: December 2004

AbstractA new method is presented to precipitate proteins and amino acids from reverse micelles by dehydrating the micelles with molecular sieves. Nearly complete precipitation is demonstrated for α‐chymotrypsin, cytochromec, and trytophan from 2‐ethylhexyl sodium sulfosuccinate (AOT)/isooctane/water reverse micelle solutions. The products precipitate as a solid powder, which is relatively free of surfactant. The method does not require any manipulation of pH, ionic strength, temperature, pressure, or solvent composition, and is applicable over a broad range of these properties. This general approach is compared with other techniques. This general approach is compared with other techniques for the recovery of biomolecules from reverse micelles. © 1994 John Wiley & Sons, Inc.
Stoichiometric model of the aerobic metabolism 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

AbstractIn the aerobic phase of the biological phosphorus removal process, poly‐β‐hydroxybutyrate, produced during anaerobic conditions, is used for cell growth, phosphate uptake, and glycogen formation. A metabolic model of this process has been developed. The yields for growth, polyphosphate and glycogen formation are quantified using the coupling of all these conversions to the oxygen consumption. The uptake of phosphate and storage as polyphosphate is shown to have a direct effect on the observed oxygen consumption in the aerobic phase. The overall energy requirements for the P‐metabolism are substantial: 25% of the acetate consumed during anaerobic conditions and 60% of the oxygen consumptions is used for the synthesis of polyphosphate and glycogen. © 1994 John Wiley & Sons, Inc.
New catalytic properties of monoamine oxidase immobilized in Langmuir–blodgett films with amphiphilic polyelectrolytes
Authors: Barmin Anatoli V. , Eremenko Arkadi V. , Kurochkin llya N. , Moskvitina Tatyana A. 
Published: December 2004

AbstractLangmuir‐Blodgett (LB) films of monoamine oxidase (MAO) have been formed on the surface f a polypropylene membrane using amphiphilic polyelectrolytes. The enzyme activity of such protein‐polyelectrolyte films was measured by a Clark electrodes. It was shown that in LB films thus formed the use of amphiphilc polyelectrolytes, MAO activity was higher than in polyelectrolyte‐free LB films. Immobilization of MAO with branched polyethylenimine modified on 12% by laurylchain led to pronounced changes in its catalytic properties. The dependence of the enzyme's kinetic parameters on amphiphilic polyelectrolyte structures was discussed. © 1994 John Wiley & Sons, Inc.
Continuous, real‐time monitoring of the oxygen uptake rate (OUR) in animal cell bioreactors
Authors: Yoon Sung‐jin , Konstantinov Konstantin B. 
Published: December 2004

AbstractA new method for real‐time monitoring of the oxygen uptake rate (OUR) in bioreactors, based on dissolved oxygen (DO) measurement at two points, has been developed and tested extensively. The method has several distinct advantages over known techniques.It enables the continuous and undisturbed monitoring of OUR, which is conventionally impossible without gas analyzers. The technique does not require knowledge of kLa. It provides smooth, robust, and reliable signal. The monitoring scheme is applicable to both microbial and mammalian cell bioprocesses of laboratory or industrial scale. The method was successfully used in the cultivation of NSO‐derived murine myeloma cell line producing monoclonal antibody. It was found that while the OUR increased with the cell density, the specific OUR decreased to approximately one‐half at cell concentrations of 16 × 106 cells/mL, indicating gradual reduction of cell respiration activity. Apart from the laboratory scale cultivation, the method was applied to industrial scale perfusion culture, as well as to processes using other cell lines. © 1994 John Wiley & Sons, Inc.