bluuebunny/crossref_metadata_2025_split huggingface dataset:
On‐line characterization of a hybridoma cell culture process
Authors: Zhou Weichang , Hu Wei‐Shou 
Published: December 2004

AbstractThe on‐line determination of the physiological state of a cell culture process requires reliable on‐line measurements of various parameters and calculations of specific rates from these measurements. The cell concentration of a hybridoma culture was estimated on‐line by measuring optical density (OD) with a laser turbidity probe. The oxygen uptake rate (OUR) was determined by monitoring dynamically dissolved oxygen concentration profiles and closing oxygen balances in the culture. The base addition for neutralizing lactate produced by cells was also monitored on‐line via a balance. Using OD and OUR measurements, the specific growth and specific oxygen consumption rates were determined on‐line. By combining predetermined stoichiometric relationships among oxygen and glucose consumption and lactate production, the specific glucose consumption and lactate production rates were also calculated on‐line. Using these on‐line measurements and calculations, the hybridoma culture process was characterized on‐line by identifying the physiological states. They will also facilitate the implementation of nutrient feeding strategies for fed‐batch and perfusion cultures. © 1994 John Wiley & Sons, Inc.
A fast bioassay for phytotoxicity measurements using immobilized photosynthetic membranes
Authors: Loranger Chantal , Carpentier Robert 
Published: December 2004

AbstractThe potential of thylakoid membranes immobilized in an albumin‐glutaraldehyde crosslinked matrix in a fast bioassay for phytotoxicity measurements in aqueous samples is studied. Free and immobilized preparations are compared for their electron transport activity measured as the initial rate of oxygen evolution with 2,5‐cichlorobenzoquinone as the artificial electron acceptor. Immobilized thylakoids were much stable under storage conditions; in the dark, at 4°C, they were fully stable in terms of photosynthetic activity for a period of 200 h. The immobilized membranes were as sensitive as the free thylakoids for the detection of most of the compounds tested (metal cations, sulfite, nitrite, and herbicides), all known as inhibitors of photosynthetic electron transport. In some instances, the immobilized preparations were even more sensitive than the free counterparts. The sensitivity could be further increased by lowering chlorophyll concentration in the assay. The short incubation period required (∼10 to 15 min) and the small volume of the assay (3 mL) suggest that this type of material should be useful in the detection of locations or effluents with phytotoxic character. © 1994 John Wiley & Sons, Inc.
Kinetics of taxol production, growth, and nutrient uptake in cell suspensions of Taxus cuspidata
Authors: Fett‐Neto Arthur G. , Zhang Wen Yi , Dicosmo Frank 
Published: December 2004

AbstractCell culture of Taxus cuspidata may represent an alternative to extraction of bark as a source of taxol and related taxanes. Cell suspensions of a cell line of T. cuspidata were grown for 44 days in shake flasks containing B5C2 medium. Throughout the growth cycle, fresh and dry weight accumulation, taxol yield on a dry weight basis, taxol accumulation in the medium, pH and pigmentation variation in the medium, as well as the uptake of sucrose, glucose, fructose, nitrate, and inorganic phosphate from the culture medium were examined. The results showed that the growth was relatively slow (doubling times of 17 and 20 days for fresh and dry weight, respectively), and taxol accumulation in the cells was non‐growth related (higher in the stationary phase) and at relatively low levels (up to 4 μg/g of the extracted dry weight). Taxol concentration in the medium had two peaks: one during the early (0.4μg/mL) and another during the late (0.1‐μg/mL) parts of the growth cycle. On a volumetric basis, the average total amount of taxol produced during the stationary phase (day 38) was 0.15 μg/mL, of which approximately 66% was in the medium and 34% was in the cells. Total carbohydrate uptake was closely associated with the increase in dry biomass. Sucrose was apparently extracellularly hydrolyzed after the first 6 days of culture; glucose was used before fructose. Nitrate was assimilated throughout the growth cycle, but phosphate was absorbed within the first week of culture. The pH variation showed an initial drop followed by a trend toward alkalinization for most of the growth period. Dark pigmentation in the medium increased progressively, particularly during the stationary phase. © 1994 John Wiley & Sons, Inc.
Biological destruction of CCI4: II. Kinetic modeling
Authors: Hooker Brain S. , Skeen Rodney S. , Petersen James N. 
Published: December 2004

AbstractA denitrifying consortium capable of transforming carbon tetrachloride (CCI4) was cultured from an aquifer soil sample from the U.S. Department of Energy's Hanford Site in southeastern Washington State. A mathematical description of the kinetics of CCI4 destruction by this microbial consortium is presented, and its prediction are compared to experimental data. The model successfully predicted the concentrations of acetate, nitrate, nitrite, biomass, and CCI4 for all 12 experiments (a total of 60 concentration‐vs.‐time data sets). In addition, no statistically significant interactions exist between parameter values and individual test conditions. The ability of the model to predict the results of a treatability test for CCI4 degradation in Hanford groundwater, without adjusting any model parameters, is discussed. © 1994 John Wiley & Sons, Inc.
Kinetic investigation of microbial souring in porous media using microbial consortia from oil reservoirs
Authors: Chen Ching‐I , Reinsel Mark A. , Mueller Robert F. 
Published: December 2004

AbstractMicrobial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60°C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso‐ and n‐butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H2S production rate were found at the from part of the reactor column after H2S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H2S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H2S production rate) in the present reactor after H2S production had stabilized was calculated to be 11062 ±2.22 mg sulfate‐S/day g biomass. © 1994 John Wiley & Sons, Inc.
Monitoring of ethanol during fermentation of a lignocellulose hydrolysate by on‐line microdialysis sampling, column liquid chromatography, and an alcohol biosensor
Authors: Buttler Torbjörn , Gorton Lo , Jarskog Helena , Marko‐Varga György , Hahn‐HäGerdal Bärbel , Meinander Nina , Olsson Lisbeth 
Published: December 2004

AbstractDuring a 70‐h fermentation of a lignocellulose hydrolysate, the ethanol produced was monitored on‐line using a microdialysis probe as an in situ sampling device. The dialysate components were then separated in a column liquid chromatographic system and the ethanol was selectively detected by an amperometric alcohol biosensor. The result was compared with two off‐line analysis methods: one chromatographic method with refractive index (RI) detection and one enzymatic method based on spectrophotometric detection. The two methods base on enzymes were shown to give lower values than the chromatographic method based on RI detection, which is discussed n terms of selectivity. The investigated on‐line setup was found to be a flexible system for monitoring of fermentations, allowing a sampling frequency of at least 12 h−1 and with a delay between sampling and detection of less than 5 min. © 1994 John Wiley & Sons, Inc.
Effects of medium carbon‐to‐nitrogen ratio on biofilm formation and plasmid stability
Authors: Huang Ching‐Tsan , Peretti Steven W. , Bryers James D. 
Published: December 2004

AbstractBiofilm formation and plasmid segregational instability in biofilm cultures of Escherichia coli DH5α (pMJR1750) were investigated under different medium‐carbon‐to‐nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid‐bearing and plasmid‐free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm2 by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7μg alginate equivalent/cm2 prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 μg alginate equivalent/cm2 at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 μg/cm2, respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 μg/cm2, respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 μg polysaccharide/μg protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 μg polysaccharide/μg protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 ± 0.011, 0.020 ± 0.006 and 0.122 ± 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 ± 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. © 1994 John Wiley & Sons, Inc.
Mass transfer limitation of sulfate in methanogenic aggregates
Authors: Overmeire Ann , Lens Piet , Verstraete Willy 
Published: December 2004

AbstractThe role of mass transfer limitation of sulfate as a factor governing the competition between sulfate reducing and methane producing bacteria in methanogenic aggregates was theoretically evaluated by the calculation of steady‐state sulfate microprofiles using a reference set of parameters obtained from the literature. The shooting method was used as a numerical technique for solving the mathematical model. The effect of the parameters on mass transport limitation was tested by varying each reference value of the parameters with a factor of 3. Sulfate limitation within granules prevailed at moderate (0.1 kg m−3) and low sulfate concentrations in the bulk liquid, at high maximum sulfate utilization rates (3.73 × 10−5 kg SO kg−1 VSS S−1 or biomass concentrations (40 KG VSS m−3), and in large aggregates (radius of 7.5 10−4 m). The effective diffusion coefficient of sulfate and the affinity constant were less determinative for the penetration depth of sulfate within a granule. © 1994 John Wiley & Sons, Inc.
Novel redox surfactants and their interactions with glucose oxidase of Aspergillus niger
Authors: Saudan Pascale , Zakeeruddin Shaik Mohammed , Malavallon Muriell‐Anne , Grätzel Michael , Fraser David Michael 
Published: December 2004

AbstractA number of novel redox surfactants (based on mixed bipyridine/dipyridylamine complexes of osmium (II) where the dipyridylamine ligands bears a saturated C8, C10, C12, C14, or C16 alkyl chain) were synthesized and characterized electrochemically and biochemically as mediators for glucose oxidase (EC 1.1.3.4, GOD) of Aspergillus niger. These compounds exhibited critical micelle concentrations (CMCs) in phosphate‐buffered saline solution (pH 7.4) in the range 10−4 10 10−3 M, the value decreasing with increasing chain length. Dependence of a number of properties (speed of mediation, redox potential, denaturing action on the enzyme, adsorption on an electrode surface) on the length of the mediator alkyl chain was observed. The presence of an alkyl chain decreased the rate of mediation relative to otherwise similar nonsurfactant mediators, and the longer alkyl chain, the slower the rate of mediation. For each compound, mediation above the CMC was about tenfold slower than that observed below the CMC. However, for the cases of mediator absorbed on an electrode surface with GOD, longer chains give increased physisorption of mixed micelles of enzyme and mediator. The compounds were incidentally found to inhibit the glucose oxidase activity of GOD in a complex manner; inhibition increased with increasing chain length and the deactivation, for any given compound, was more pronounced below the CMC than above. Glucose oxidase activity assays and study of the action of surfactants and mediators on the fluorescent properties of carboxy‐fluorescein‐labeled GOD led to the consideration of a model for redox surfactant‐GOD interaction where three mechanisms may operate: first, a selective interaction of mediators with the GOD active site; second, a nondenaturing association of short‐chain (<C14) cationic surfactants; and third, a denaturing action of long‐chain (⪆C14) cationic surfactants. © 1994 John Wiley & Sons, Inc.
Metabolic monitoring by using the rate of change of NAD(P)H fluorescene
Authors: Kwong Simon C. W. , Rao Govind 
Published: December 2004

AbstractThe amino acid fermentation by Corynebacterium glutamicum was monitored with an new technique that uses the first derivative of the NAD(P)H fluorescene signal. The rate of change of NAD(P)H pools is indicative of intracellular redox balance variations that correspond to metabolic changes. The profile of this signal showed several characteristics that coincided with major metabolic events during fermentation. We show here that the derivative fluorescence signal can accurately estimate points of threonine depletion, viable cell count, and the end of amino acid formation. Furthermore, on‐line optimization strategies can be developed by using the derivative fluorescene signal. © 1994 John Wiley & Sons, Inc.
Examination of primary metabolic pathways in a murine hybridoma with carbon‐13 nuclear magnetic resonance spectroscopy
Authors: Mancuso Anthony , Sharfstein Susan T. , Tucker Sean N. , Clark Douglas S. , Blanch Harvey W. 
Published: December 2004

AbstractPrimary metabolism of a murine hybridoma was probed with 13C nuclear magnetic resonance (NMR) spectroscopy. Cells cultured in a hollow fiber bioreactor were serially infused with [1−13C] glucose, [2−13C] glucose, and [3−13C] glutamine. In vivo spectroscopy of the culture was used in conjunction with off‐line spectroscopy of the medium to determine the intracellular concentration of several metabolic intermediates and to determine fluxes for primary metabolic pathways. Intracellular concentrations of pyruvate and alanine were very high relative to levels observed in normal quiescent mammalian cells. Estimates made from labeling patterns in lactate indicate that 76% of pyruvate is derived directly from glycolysis; some is also derived from the malate shunt, the pyruvate/melate shuttle associated with lipid synthesis and the pentose phosphate pathway. The rate of formation of pyruvate from the pentose phosphate pathway was estimated to be 4% of that from glycolysis; This value is a lower limit and the actual value may be higher. Incorporation of pyruvate into the tricarboxylic acid (TCA) cycle appears to occur through only pyruvate dehydrogenase; no pyruvate carboxylase activity was detected. The malate shunt rate was approximately equal to the rate of glutamine uptake. The rate of incorporation of glucosederived acetyl‐CoA into lipids was 4% of the glucose uptake rate. The TCA cycle rate between isocitrate and α‐ketoglutarate was 110% of the glutamine uptake rate. © 1994 John Wiley & Sons, Inc.
Biological sulphate reduction using gas‐lift reactors fed with hydrogen and carbon dioxide as energy and carbon source
Authors: van Houten Renze T. , Pol Look W. Hulshoff , Lettinga Gatze 
Published: December 2004

AbstractFeasibility and engineering aspects of biological sulphate reduction in gas‐lift reactors were studied. Hydrogen and carbon dioxide were used as energy and carbon source. Attention was paid to biofilm formation, sulphide toxicity, sulphate conversion rate optimization, and gasliquid mass transfer limitations. Sulphate‐reducing bacteria formed stable biofilms on pumice particles. Biofilm formation was not observed when basalt particles were used. However, use of basalt particles led to the formation of granules of sulphate‐reducing biomass. The sulphate‐reducing bacteria, grown on pumice, easily adapted to free H2S concentrations up to 450 mg/L. Biofilm growth rate then equilibrated biomass loss rate. These high free H2S concentrations caused reversible inhibition rather than acute toxicity. When free H2S concentrations were kept below 450 mg/L, a maximum sulphate conversion rate of 30 g SO42−/L · d could be achieved after only 10 days of operation. Gas‐to‐liquid hydrogen mass transfer capacity of the reactor determined the maximum sulphate conversion rate. © 1994 John Wiley & Sons, Inc.
Protein extraction by reverse micelles: Studies on the recovery of horseradish peroxidase
Authors: Regalado Carlos , Asenjo Juan A. , Pyle D. Leo 
Published: December 2004

AbstractPhase transfer studies were carried out on the solubilization of horseradish peroxidase (HRP) (E.C. 1.11.1.7) in reverse micelles formed in isooctane using the anionic surfactant, aerosol OT, at concentrations between 50 and 110mM. The selectivity of this methodology was tested, because the HRP used comprised a mixture of seven different isoenzymes with a wide range of isoelectric points. Forward and backward transfers were carried out in wellstirred vessels until equilibrium was reached. Significant protein partitioning could only be obtained by using NaCl to adjust ionic strength in pH range between 1.5 and 3.5, with a maximum at pH 3. The back transfer process was best at pH 8 with 80mM phosphate buffer and 1 M KCI. A loss of 1% to 3% of the surfactant through precipitation at the interface at pH<4 was observed, which may be due to instability in this pH region, because, even without protein, a similar precipitate was noticed. Protein partitioning was approximately constant when the ionic strength was increased up to 1 MNaCl at pH 3, but protein recovery in back transfer decreased accordingly. Hydrophobic interactions together with association between the protein and surfactant might be responsible for that behavior. Protein partitioning remained the same when the surfactant concentration was decreased to 50 mM, at the expense of higher variability. HPLC chromatograms showed no apparent damage to the protein after reverse micellar extraction. Protein partitioning is best when the temperature is kept at 25×C. The amount of protein and specific activity recovered strongly depends on the phase ratio used during forward transfer. Overall activity recovery varied from 87% to 136% when the phase ratio was increased from 1:1 to 30:1 in forward transfer. This behavior may be due to a change in the ratio of the three isoenzymes recovered after the backward transfer process, with the most active one being increasingly enriched at higher phase ratios. © 1994 John Wiley & Sons, Inc.
Catabolic control of hybridoma cells by glucose and glutamine limited fed batch cultures
Authors: Ljunggren Jan , Häggström Lene 
Published: December 2004

AbstractSubstrate limited fed batch cultures were used to study growth and overflow metabolism in hybridoma cells. A glucose limited fed batch, a glutamine limited fed batch, and a combined glucose and glutamine limited red batch culture were compared with batch cultures. In all cultures μ reaches its maximum early during growth and decreases thereafter so that no exponential growth and decreases thereafter so that no exponential growth rate limiting, although the glutamine concentration (>0.085mM) was lower than reported Ks vales and glucose was below 0.9mM; but some other nutrients (s) was the cause as verified by simulations. Slightly more cells and antibodies were produced in the combined fed batch compared with the batch culture. The specific rates for consumption of glucose and glutamine were dramatically influenced in fed batch cultures resulting in major metabolic changes. Glucose limitation decreased lactate formation, but increased glutamine consumption and ammonium formation. Glutamine limitation decreased ammonium and alanine formation of lactate, alanine, and ammonium was negligible in the dual‐substrate limited fed batch culture. The efficiency of the energy metabolism increased, as judged by the increase in the cellular yield coefficient for glucose by 100% and for glutamine by 150% and by the change in the metabolic ratios lac/glc, ala/ln, and NHx/ln, in the combined fed culture. The data indicate that a larger proportion of consumed glutamine enters the TCA cycle through the glutamate dehydrogenase pathway, which releases more energy from glutamine than the transamination pathway. We suggest that the main reasons for these changes are decreased uptake rates of glucose and glutamine, which in turn lead to a reduction of the pyruvate pool and a restriction of the flux through glutaminase and lactate dehydrogenase. There appears to be potential for further cell growth in the dual‐substrate‐limited fed batch culture as judged by a comparison of μ in the different cultures. © 1994 John Wiley & Sons, Inc.
Efficient Hydrogen photoproduction by synchronously grown cells of a marine cyanobacterium, Synechococcus sp. Miami BG 043511, under high cell density conditions
Authors: Kumazawa Shuzo , Mitsui Akira 
Published: December 2004

AbstractThe capability of hydrogen photoproduction under high cell density conditions was examined using synchronously grown cells of nitrogen‐fixing Synechococcus sp. Miami BG 043511. Optimum hydrogen yield was obtained when vessels (25 ml) contained 0.2 to 0.3 mg chlorophyll a in 3‐mL cell suspension. During a 24‐h incubation period, an initial phase of hydrogen and carbon dioxide production and a subsequent phase of carbon dioxide uptake and oxygen accumulated as major products after 24 h. after the initial 24‐h. After the initial 24‐h incubation, as high as 7.4 and 3.7 L (at standard condition) of hydrogen and oxygen, respectively, accumulated in vessels with 22‐ml gas phase. This indicated that the pressure in the flask increased to 1.5 atmosphere. Energy conversion efficiency based on photosynthetically active radiation (25 W/m2) was about 2.6%. However, increased pressure somehow reduced the duration of hydrogen production. Duration of hydrogen and oxygen production was prolonged by periodical (24‐h interval) gas replacement during incubation. © 1994 John Wiley & Sons, Inc.