bluuebunny/crossref_metadata_2025_split huggingface dataset:
Affinity precipitation of an antibody by ligand‐modified phospholipids
Authors: Powers Daniel D. , Carbonell Ruben G. , Kilpatrick Peter K. 
Published: December 2004

AbstractA new method for the selective precipitation of proteins is applied to the isolation and purification of an antibody. Ligand‐modified phospholipids (LMPs) are solubilized by the nonionic ethoxylated alcohol detergent, resulting in small (50 to 100 Å) micellar aggregates of LMPs and surfactant. When introduced into protein solutions containing an antibody for which the LMP has specific affinity, the ligand binds to the protein. Hydrophobic interactions between phospholipid tail groups bound to the protein molecules result in an insoluble precipitate. Polyclonal and monoclonal antibiotin antibody (pABA and mABA) are shown to be selectively precipitated using ratios of dimyristoylphosphatidylethanolamidobiotin (DMPE‐B) to ABA ranging from 1:1 to 19:1. The kinetics and yield of the precipitation achieve a maximum at a ratio of DMPE‐B to ABA of approximately 7:1. The kinetics and magnitude of the turbidity change are modeled using the Mie theory of light scattering coupled with the smoluchowski theory of aggregation. The kinetics are shown to be enhanced significantly by the addition of salt. In particular, the addition of 0.5 M ammonium sulfate salt increases the rate of precipitation by more than an order of magnitude. It is demonstrated that pABA can be recovered with total activity yields of 60% to 70% from mixtures containing nonspecific lgG antibodies in very high purity (>99%). © 1994 John Wiley & Sons, Inc.
Frequent harvesting from perfused bone marrow cultures results in increased overall cell and progenitor expansion
Authors: Oh Duk Jae , Koller Manfred R. , Palsson Bernhard O. 
Published: December 2004

AbstractThe establishment of prolific long‐term human bone marrow cultures has led to the development of hematopoietic bioreactor systems. A single batch expansion of bone marrow mononuclear cell populations leads to a 10‐ to 30‐fold increase in total cell number and in the number of colony forming units‐granulocyte/macrophage (CFU‐GMs), and a four‐ to tenfold increase in the number of long‐term culture initiating cells (LTC‐ICs). In principle, unlimited expansion of cells should be attainable from a pool of stem cells if all the necessary requirements leading to stem cell maintenance and division are met. In this article, we take the first step toward the identification of factors that limit single batch expansion of ex vivo bone marrow cells in perfusion‐based bioreactor systems. One possible constraint is the size of the growth surface area required. This constraint can be overcome by harvesting half the cell population periodically. We found that harvesting cells every 3 to 4 days, beginning on day 11 of culture, led to an extended growth period. Overall calculated cell expansion exceeded 100‐fold and the CFU‐GM expansion exceeded 30‐fold over a 27‐day period. These calculated values are based on growth that could be obtained from the harvested cell population. Growth of the adherent cell layer was stable, whereas the nonadherent cell population diminished with increasing number of passages. These results show that the bioreactor protocols published to date are suboptimal for long‐term cultivation, and that further definition and refinement is likely to lead to even greater expansion of hematopoietic cell populations obtained from bone marrow. More importantly, these results show that the LTC‐IC measured during the single pass expansion do have further expansion potential that can be realized by frequent harvesting. Finally, the present culture conditions provide a basis for an assay system for the identifications provide a basis for an assay system for the identification of the factors that determine the long‐term maintenance and replication of human stem cells ex vivo. © 1994 John Wiley & Sons, Inc.
Linear constrain relations in biochemical reaction systems III. Sequential application of data reconciliation for sensitive detection of systematic errors
Authors: van der Heijden R. T. J. M. , Romein B. , Heijnen J. J. , Hellinga C. , Luyben K. C. A. M. 
Published: December 2004

AbstractThis article presents a method to test the presence of relatively small systematic measurement errors; e.g., those caused by inaccurate calibration or sensor drift. To do this, primary measurements—flow rates and concentrations—are first translated into observed conversions, which should satisfy several constraints, like the laws of conservation of chemical elements. This study considers three objectives:

Modification of the commonly used balancing technique to improve error sensitivity to be able to detect small systematic errors. To this end, the balancing technique is applied sequentially in time.
Extension of the method to enable direct diagnosis of errors in the primary measurements instead of diagnosing errors in the observed conversions. This was achieved by analyzing how individual errors in the primary measurements are expressed in the residual vector.
Derivation of a new systematic method to quantitatively determine the sensitivity of the error, is that error size at which the expected value of the chisquare test function equals its critical value.
The method is applied to industrial data demonstrating the effectiveness of the approach. It was shown that, for most possible error sources, a systematic errors of 2% to 5% could be detected. In given application, the variation of the N‐content of biomass was appointed to be the cause of errors. © 1994 John Wiley & Sons, Inc.
Multiple product inhibition and growth modeling of clostridium butyricum and klebsiella pneumoniae in glycerol fermentation
Authors: Zeng A.‐P. , Ross A. , Biebl H. , Tag C. , Günzel B. , Deckwer W.‐D. 
Published: December 2004

AbstractThe inhibition potentials of products and substrate on the growth ofClostridium butyricum and Klebsiella pneumoniae in the glycerol fermentation are examined from experimental data and with a mathematicalmodel. Whereas the inhibition potential of externally added and self‐produced 1,3‐propanediol is essentially the same, butyric acid produced by the culture is more toxic than that externally added. The same seems to apply for acetic acid. The inhibitory effect of butyric acid is due tothe total concentration instead of its undissociated form. For acetic acid, it cannot be distinguished between the total concentration and the undissociated formThe inhibition effects of products and substrate in the glycerol fermentation are irrespective of the strains, and, therefore, the same growth model can be used. The maximum product concentrations tolerated (critical concentrations C*pi) are 0.35 g/Lfor undissociated acetic acid, 10.1 g/L for total butyric acid, 16.6 g/L for ethanol, 71.4 g/L for 1,3‐propanediol, and 187.6 g/L for glycerol, which are applicable to C. butyricum and K. pneumoniae grown under a variety of conditions. For 55 steady‐states, which were obtained from different types of continuous cultures over a pHrange of 5.3–8.5 and under both substrate limitation and substrate excess, the proposed growth model fits the experimental data with an average deviation of 17.0%. The deviation of model description from experimental values reduces of 11.4% if only the steady‐states with excessive substrate are considered. © 1994 John Wiley & Sons, Inc.
Production of somatic embryos in a helical ribbon impeller bioreactor
Authors: Archambault Jean , Williams Robert D. , Lavoie Luc , Pépin Marie‐France , Chavarie Claude 
Published: December 2004

AbstractEmbryogenic cultures of a transformed Eschscholtzia californica cell line were carried out in a 11‐L helical ribbon impeller bioreactor operated under various conditions to evaluate the performance of this equipment for somatic embryo (SE) production. All bioreactor cultures produced SE suspensions with maximum concentrations at least comparable to those obtained from flask control cultures (∼8–13 SE · mL−;1). However, an increase of the mixingspeed, from 60 to 100 rpm, and low sparging rate (∼0.05 VVM, kL a ∼ 6.1 h−;1) for dissolved oxygen concentration (DO) control yielded poorer quality embryogenic cultures. The negative effects on SE production were attributed mainly to the low but excessive shear experienced by the embryogenic cells and/or embryoforming aggregates. High DO (∼60% of air saturation) conditions favored undifferentrated biomass production and high nutrient uptake rates at the expense of the slower SE differentiation process in both flask and bioreactor cultures. Too low DO (−5–10%) inhibited biomass and SE production. The best production of SE (∼44 SE · mL−1 or ∼757 SE · g dw−1 · d−1) was achieved by operating the bioreactor at 60 rpm while controlling DO at ∼20%by surface oxygenation only (0.05 VVM, kL a ∼ 1.4 h−;1). This production was found to be a biomass production/growth‐associated process and was mainly limited by the availability of extracellular phosphate, magnesium, nitrogen salts, and carbohydrates. © 1994 John Wiley & Sons, Inc.
Effect of modified glucose uptake using genetic engineering techniques on high‐level recombinant protein production in escherichia coli dense cultures
Authors: Chou Chih‐Hsiung , Bennett George N. , San Ka‐Yiu 
Published: December 2004

AbstractReduction of acetate excretion using a modified cellular glucose uptake rate was examined. An Escherichia coli strain bearing a mutationin ptsG, a gene encoding enzyme II in glucose phosphotransferase system (PTS), was constructed and characterized. The growth rate of the mutant strain was slower than its parent in glucose defined medium, butwas not affected in complex medium. Experimental results using this mutant strain showed a significant improvement in culture performance in simple batch cultivations due to reduced acetate excretion through the modified glucose uptake. Both biomass and recombinant protein productivity were increased by more than 50% with the ptsG mutant when compared to the parent strain. Recombinant protein productivity by the newly constructed strain at a level of more than 1.6 g/L was attained consistently in a simple batch bioreactor. © 1994 John Wiley & Sons, Inc.
Biosorption of mercury by the inactivated cells of pseudomonas aeruginosa PU21 (Rip64)
Authors: Chang Jo‐Shu , Hong Juan 
Published: December 2004

AbstractBiomass of a mercury‐resistant strain Pseudomonas aeruginosa PU21 (Rip64) and hydrogen‐form cation exchange resin (AG 50W‐X8) were investigated for their ability to adsorb mercury. The maximum adsorption capacity was approximately 180 mg Hg/g dry cell in deionized water and 400 mg Hg/g dry cell in sodium phosphate solution at pH 7.4, higher than the maximum mercury uptake capacity in the cation exchange resin (100 mg Hg/g dry resin in deionized water). The mercury selectivity of the biomass over sodium ions was evaluated when 50 mM and 150 mM of Na+ were present. Biosorption of mercury was also examined in sodium phosphate solution andphosphate‐buffered saline solution (pH 7.0), containing 50mM and 150 mM of Na+, respectively. It was found that the presence of Na+ did not severely affect the biosorption of Hg2+, indicating a high mercury selectivity ofthe biomass over sodium ions. In contrast, the mercury uptake by the ion exchange resin was strongly inhibited by high sodium concentrations. The mercury biosorption was most favorable in sodium phosphate solution (pH 7.4), with a more than twofold increase in the maximum mercury uptake capacity. The pH was found to affect the adsorption of Hg2+bythe biomass and the optimal pH value was approximately 7.4. The adsorption of mercury on the biomass and the ion exchange resin appeared to follow theLangmuir or Freundlich adsorption isotherms. © 1994 John Wiley & Sons, Inc.
The influence of dissolved oxygen tension on the synthesis of the antibiotic difficidin by bacillus subtilis
Authors: Suphantharika M. , Ison A. P. , Lilly M. D. , Buckland B. C. 
Published: December 2004

AbstractThe antibiotic, difficidin, and its hydroxylated derivative oxydifficidin, were synthesized by cultures of Bacillus subtilis grown on a complex medium. Maximum titers of about 200 and 130 mg/L, respectively, were obtained. In fermentations where the dissolved oxygen tension (DOT) was controlled, the maximum specific growth rate was only reduced below 5% air saturation. DOT had little effect on the volumetric rateof synthesis of oxydifficidin but greatly influenced the rate for difficidin, which was reduced at DOT values below 40% air saturation. © 1994 John Wiley & Sons, Inc.
Characterization of compost biofiltration system degrading dichloromethane
Authors: Ergas Sarina. J. , Kinney Kerry , Fuller Mark E. , Scow Kate M. 
Published: December 2004

AbstractThe effects of acclimatization of microbial populations, compound concentration, and media pH on the biodegradation of low concentration dichloromethane emissions in biofiltration systems was evaluated. Greater than 98% removal efficiency was achieved for dichloromethane at superficial velocities from 1 to 1.5 m3/m3. min (reactor residence times of 1 and 0.7 min, respectively) and inlet concentrations of 3 and 50 ppm Although acclimatization of microbial populations to toluene occurred within 2 weeks of operation start‐up, initial dichloromethane acclimatization took place over a period of 10 weeks. This period was shortened to 10 days when a laboratory grown consortium of dichloromethane degrading organism, isolated from a previously acclimatized column, was introduced into fresh biofilter media. The mixed culture consisted to 12 members, which together were able to degrade dichloromethane at concentrations up to 500 mg/L. Only one member of the consortium was able to degrade dichloromethane were sustained for more than 4 months in a biofilter column receiving an inlet gas stream with 3 ppmv of dichloromethane acidification of the column and resulting decline in performance occurred when a 50‐ppmv inlet concentration was used. A biofilm model incorporating first order biodegradation kinetics provided a good fit to observed concentration profiles, and may prove to be a useful tool for designing biofiltration systems for low concentration VOC emissions. © 1994 John Wiley & Sons, Inc.
Induction of apoptosis in nutrient‐deprived cultures of hybridoma and myeloma cells
Authors: Mercille Sylvain , Massie Bernard 
Published: December 2004

AbstractIn the present study, cell death was investigated in cultures of NS/0 myelomas and SP2/0‐derived D5 hybridomas through morphological examination of cells stained with acridine orange and ethidium bromide. The relative contribution of elevated levels of lactic acid and ammonia, as well as deprivation of glutamine, cystine, and glucose on the induction of necrosis or apoptosis, was investigated. In batch culture of D5 hybridoma cells, induction of apoptotic cell death correlated with the exhaustion of glutamine, while in the case of NS/0 myelomas, it coincided with exhaustion of cystine. To determine whether limiting nutrients were the actual triggering factors for apoptosis in batch culture, exponentially growing cells were resuspended in glutamine or cystine‐free media. Within 30 to 40 h, viability decreased to 50% and the nonviable cell population displayed typical apoptotic morphology, with crescents of condensed chromatin around the periphery of the nucleus, or with the entire nucleus present as one or a group of featureless, brightly staining spherical beads. Similarly, D5 hybridomas and NS/0 myelomas cultivated in glucose‐free medium died mainly from apoptosis. Cells were also cultivated in fresh medium supplemented with elevated concentrations of ammonia (3.0 mM) and/or lactate (35 mM, 50 mM). This resulted in decreased viabilities and necrotic death in both cell lines. From these results, we conclude that D5 hybridomas and NS/0 myelomas deprived of essential nutrients die by apoptosis, whereas incubation in the presence of elevated levels of metabolic byproducts such as ammonia and lactate will induce necrotic cell death in these cells. © 1994 John Wiley & Sons, Inc.
Physiological responses of hybridoma cells in a protein‐free medium to soluble and immobilized antigen
Authors: Dandulakis Gregory , Herr John C. , Kirwan Donald J. 
Published: December 2004

AbstractThis study examined the effect of antigen in a protein free medium on cell growth and monoclonal antibody production by a hybridoma line. Antigen immobilized on a Sepharose gel matrix via a bovine γ‐globulin carrier protein was used to stimulate the cell cultures in T‐flasks. In comparison to antigen‐free culture, total antibody production during was increased up to 40%, while slower cell growth rates were observed. The specific antibody production during the stationary culture phase was 40% to 80% higher in the presence of immobilized antigen. The surface density of antigen on the Sepharose beads had a strong influence on the physiological response of the hybridomas. © 1994 John Wiley & Sons, Inc.
Membrane bioreactor with a porous hydrophobic membrane as a gas–liquid contactor for waste gas treatment
Authors: Reij Martine W. , de Bont Jan A. M. , Hartmans Sybe , de Gooijer Kees D. 
Published: December 2004

AbstractA novel type of bioreactor for waste gas treatment has been designed. The reactor contains a microporous hydrophobic membrane to create a large interface between the waste gas and the aqueous phase. To test the new reactor, propene was chosen because of its high air/water partition coefficient, which causes a low water concentration and hampers its removal from air. Propene transfer from air to a suspension of propene‐utilizing Xanthobacter Py2 cells in the membrane bioreactor proved to be controlled by mass transfer in the liquid phase. The resistance of the membrane was negligible. Simulated propene transfer rates agreed well with the experimental data. A stable biofilm of Xanthobacter Py2 developed on the membrane during prolonged operation. The propene flux into the biofilm was 1 × 10−6 mol m−2 s−1 at a propene concentration of 9.3 × 10−2 mol m−3 in the gas phase. © 1995 John Wiley & Sons, Inc.
On‐line calibration of a computerized biosensor system for continuous measurements of glucose and lactate
Authors: Kyröläinen Marika , Håkanson Håkan , Mattiasson Bo 
Published: December 2004

AbstractAn on‐line calibration procedure for application in continuous monitoring systems has been developed. Control of the calibration value and recalibration on‐line during monitoring is possible without having to disrupt the sample withdrawal. The calibration procedure has been applied and evaluated in a continuous biosensor system based on the detection of oxygen depletion during enzymatic substrate conversion by immobilized oxidases. Evaluation included on‐line calibration during continuous measurements of glucose and lactate in bovine blood samples. Calibration of the complete system consisting of a sampling device, a sample handling step, a biocatalytic step, a detection step, and a data processing unit is performed by the on‐line addition of a calibration solution to a blank sample which is fed through the system. The calibration cycle is completed within 5.5 min. When recalibration is carried out during monitoring, the calibration solution is added to the sample, instead of to a blank sample, and the increase in outlet singl is registered. The major advantage of this internal standard principle is that the calibration solution is fed through the whole system according to the same path as the sample solution and thus takes into account all parameters influencing the sample. © 1995 John Wiley & Sons, Inc.
Influence of water activity on the synthesis of triolein catalyzed by immobilized Mucor miehei lipase
Authors: Dudal Yves , Lortie Robert 
Published: December 2004

AbstractThe influence of the thermodynamic activity of water (aw)on the synthesis of triolein catalyzed by Mucor miehei lipase was investigated. Its effect on the equilibrium and on the rates of the different reactions present, esteification and mono‐ and diglyceride isomerization, was evaluated through measurements made in controlled water activity atmosphere. The apparent equilibrium constants were measured from the concentration of the different species as a function of the intial glycerol‐to oleic‐acid ratio using all the values at once with a multi‐response nonlinear regression technique. Rate constants were determined from kinetic measurements and non‐linear regression uning the variation of the concentration of all significant species in the system. Except for the synthesis of diolein from monoolein, which shows a maximum for aw ≈ 0.5, the apparent rate constants of the various reactions are not significantly affected by the value of the water activity. The equilibrium is shifted to‐ward the synthesis of triolein for low values of aw, indicating that in the design of a process for triglyceride synthesis, using M. miehei lipase as a catalyst, the water activity can be lowered to extreme values to favor the synthesis, without any sacrifice on the productivity of the process. © 1995 John Wiley & Sons, Inc.
Serum‐free cell culture on insulin‐immobilized porous collagen beads
Authors: Ito Yoshihiro , Zheng Ji , Imanishi Yukio 
Published: December 2004

AbstractInsulin or albumin was immobilized on collagen beads using water‐soluble carbodiimide. Adhesion of STO mouse fibroblast cells onto the beads decreased with increasing the amount of immobilized proteins. Growth of the cells was remarkably accelerated on the insulinimmobilized collagen beads, which can be used for serum‐free cell culture. The growth acceleration became larger with increasing the amount of immobilized insulin, while it became smaller with increasing the amount of immobilized albumin. In addition, the immobilized insulin more strongly accelerated the cell growth than free insulin plus collagen beads. © 1995 John Wiley & Sons, Inc.
Death mechanisms of animal cells in conditions of intensive agitation
Authors: Al‐Rubeai M. , Singh R. P. , Goldman M. H. , Emery A. N. 
Published: December 2004

AbstractThe question is addressed as to whether cells which are subject to high‐energy dissipation rates in agitated bioreactors show an apoptotic response. Murine hybridoma cells in batch culture were agitated in bench‐scale (1‐L) bioreactors without gas sparging. At an energy dissipation rate of 1.5 W m−3 there was no apparent damage. At 320 W m−3 cell viability declined, and increasing proportions of the dead cells displayed the morphological features of apoptosis, but necrosis also remained as a significant mechanism of death. When cells were subjected to the intensive energy dissipation rate of 1870 W m−3 in a bioreactor without gas headspace, the cell number dropped by 50% within 2 h and a subpopulation of smaller‐sized cells emerged. This excluded trypan blue but showed some apoptotic characteristics such as reduced and condensed DNA content and low F‐actin content. The incidence of apoptotic activity was further demonstrated by the appearance of numerous apoptotic bodies. Analysis of the cell cycles of both small and normal size populations indicated that greater proportions of S and G2 cells had become apoptotic and there was evidence of preferential survival of G1 cells. It is suggested that two mechanisms of cell death are apparent in hydrodynamically stressful situations, but their relative expression depends on the energy dissipation rate. © 1995 John Wiley & Sons, Inc.