bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluid shear effects on suspension cultures of Morinda citrifolia
Authors: Kieran P. M. , O'Donnell H. J. , Malone D. M. , MacLoughlin P. F. 
Published: December 2004

AbstractThe shear susceptibility of cell suspension cultures of the plant cell Morinda citrifolia was investigated by subjecting the cells to the well‐defined shear field generated in turbulent flow through a capillary. Suspensions were circulated using a peristaltic pump and average shear stresses between 25 and 350 N m−2 were generated in the capillary test section. Control experiments were performed to assess the possible contribution of the peristaltic pump to the observed cell damage. There was clear evidence of pump‐induced damage at the more severe test conditions and all viability measurements were corrected accordingly. Both shake flask suspension cultures (aged between 9 and 15 days) and repeated batch fermentation cultures, grown in a stirred tank reactor (STR) under a variety of controlled agitation conditions, were tested in the capillary shear loop. The cell damage incurred was evaluated in terms of suspension viability, as determined by a dye exclusion technique. Viability loss was found to conform closely to a first‐order model in which the rate constant was observed to increase with the imposed shear stress. Furthermore, a linear relationship was identified between the specific death constant and the cumulative energy dissipated. Post‐shear morphological measurements showed that the chain length distribution is shifted toward markedly lower values. In comparison with shake flask cultures, repeated batch fermentation cultures exhibited a marked increase in sensitivity to capillary shear. Based upon the determined morphological characteristics, this result is primarily attributable to the increased chain lengths characteristic of the repeated batch cultures. © 1995 John Wiley & Sons, Inc.
Relation between dissolved oxygen concentration and ajmalicine production rate in high‐density cultures of Catharanthus roseus
Authors: Schlatmann J. E. , Vinke J. L. , ten Hoopen H. J. G. , Heijnen J. J. 
Published: December 2004

AbstractThe relation between dissolved oxygen (DO) and the ajmalicine production rate of Catharanthus roseus was investigated in 15‐L tank reactors at constant stirrer speed and gas flow rate. Below a DO concentration of 29% of air saturation the ajmalicine production rate was less than 0.06 μmol/g/d. Above a DO of 43% the ajmalicine production rate was constant at 0.21 μmol/g/d. Between a DO of 29% and 43% there was a strong relation between the ajmalicine production rate and the DO concentration. After a period of at least 12 days at DO ⩽29% the culture lacked the ability to adapt to a DO ⩾57%. A kinetic equation is proposed for the relation between DO and the specific ajmalicine production rate. © 1995 John Wiley & Sons, Inc.
Enhancing effect of albumin hydrolysate on ethanol production employing Saccharomyces sake
Authors: Shin Chul Soo , Song Ji Yeon , Ryu Ok Hee , Wang Shaw S. 
Published: December 2004

AbstractThe enhancing effect of albumin hydrolysate on ethanol production was investigated in ethanol fermentations using Saccharomyces sake. In batchwise ethanol production, addition of supplemental albumin hydrolysate and phosphatidylcholine, or albumin hydrolysate alone, brought about a more than 60% increase in final ethanol concentration (148 or 144 g/L compared with 88 g/L with no supplementation [control] after 72 h). The effect of the supplements is believed to be due to an enhanced alcohol tolerance of cells grown in media containing the supplements. Cells grown in media containing albumin hydrolysate were enriched in phenyalanine, tyrosine, and methionine in their plasma membranes. All three amino acids were also present in considerable amounts in the albumin hydrolysate. This fact suggests that the three amino acids, which are present in albumin hydrolysate, are incorporated into the plasma membranes of cells. Under ethanol production conditions in which only one amino acid among the components of albumin hydrolysate was excluded, namely phenlalanine, tyrosine, or methionine, significant reductions in ethanol production resulted. © 1995 John Wiley & Sons, Inc.
Dynamics of biofilm detachment in biofilm airlift suspension reactors
Authors: Tijhuis L. , van Loosdrecht M. C. M. , Heijnen J. J. 
Published: December 2004

AbstractThe dynamic change in the overall detachment rate of spherical biofilms in a biofilm airlift suspension reactor was measured after a downshift of the substrate loading rate to zero while all other conditions remained constant. In contrast to the expectations, the overall detachment rate decreased rapidly to a nearly stable level. Correlations available from literature were not able to describe this phenomenon. Concepts were formulated which can describe the observations from this study. Research under dynamic conditions and careful monitoring of the biofilm surface area and biofilm morphology are necessary to elucidate and discriminate biofilm detachment mechanisms. © 1995 John Wiley & Sons, Inc.
Effect of cDNA copy number on secretion rate of activated protein C
Authors: Guarna M. M. , Fann C. H. , Busby S. J. , Walker K. M. , Kilburn D. G. , Piret J. M. 
Published: December 2004

AbstractThe secretion rate of activated protein C (APC) by BHK cells was increased 35‐fold by increasing the cDNA copy number per cell from 50 to 240. In this range, the relation between APC secretion and cDNA copy number was not linear and the rate of APC secretion per cDNA copy increased sevenfold. This apparent cooperative effect of multiple cDNA copies could be related to their integration in tandem. For cDNA copy numbers higher than 240, the APC secreation rate per cDNA and per cell decreased dramatically. The γ‐carboxylation of glutamic acid residues, a posttranslational modification required for APC biological activity, was also investigated. The proportion of APC that was fully γ‐carboxylated decreased as the secretion rate of APC increased. © 1995 John Wiley & Sons, Inc.
Metabolic flux distributions in Penicillium chrysogenum during fed‐batch cultivations
Authors: Jørgensen Henrik , Nielsen Jens , Villadsen John , Møllgaard Henrik 
Published: December 2004

AbstractBased on a review of the Penicillium chrysogenum biochemistry a stoichiometric model has been set up. The model considers 61 internal fluxes and there are 49 intracellular metabolites which are assumed to be in pseudo–steady state. In addition to the intracellular fluxes the model considers the uptake of 21 amino acids. From the stoichiometric model the maximum theoretical yield of penicillin V is calculated to 0.43 mol/mol glucose. If biosynthesis of cysteine is by direct sulfhydrylation rather than by transsulfuration, the maximum theoretical yield is about 20% higher, i.e., 0.50 mol/mol glucose. The theoretical yield decreases substantially if α‐aminoadipate is converted to 6‐oxo‐piperidine‐2‐carboxylic acid (OPC). If only 40% of the α‐aminoadipate is recycled, the maximum theoretical yield is 0.31 mol/mol glucose. The uptake rates of glucose, lactate, γ‐aminobutyrate, and 21 amino acids were measured during fed‐batch cultivations. The rates of formation of penicillin V, δ‐(L‐α)‐aminoadipyl‐L‐cysteinyl‐D‐valine (ACV), OPC, and the pool of isopenicillin N, 6‐APA, and 8‐HPA were also measured. Finally the synthesis rates of the biomass constituents RNA/DNA, protein, lipid, carbohydrate, and amino carbohydrate were measured. From these measured rates and the stoichiometric model the metabolic fluxes through the different intracellular pathways are calculated. The calculations show that penicillin formation is accompanied by a large flux through the pentose phosphate (PP) pathway due to a large requirement for nicotinamide‐adenine dinucleotide phosphate (NADPH) used in the biosynthesis of cysteine. If cysteine is added to the medium, the flux through the PP pathway decreases. From the stoichiometric model YxATP is calculated to 87 mmol adenosine triphosphate (ATP)/g dry weight (DW), and from the flux calculations mATP is found to 3 mmol ATP/g DW/h. © 1995 John Wiley & Sons, Inc.
Reversed micellar extraction of trypsin: Effect of solvent on the protein transfer and activity recovery
Authors: Chang Qing‐long , Chen Jia‐yong 
Published: December 2004

AbstractBy using trypsin as the model protein and AOT as the model surfactant, the effect of a variety of solvents on protein transfer and activity recovery during the liquid–liquid reversed micellar extraction was investigated. It was found that several solvents, including isooctane, octane, heptane, and kerosene, had a similar effect on the recovery of trypsin activity after a full cycle of forward and backward extraction, and could all be used as the solvents for AOT‐reversed micelles in trypsin extraction. Two other solvents (hexane and cyclohexane), however, were not so efficient. © 1995 John Wiley & Sons, Inc.
Adhesion of mammalian cells to a recombinant attachment factor, CBD/RGD, analyzed by image analysis
Authors: Wierzba Andrew , Reichl Udo , Turner Robin F. B. , Warren R. Antony J. , Kilburn Douglas G. 
Published: December 2004

AbstractA luminance thresholding procedure was developed to quantify cell attachment of a variety of cell lines to CBD/RGD, a hybrid attachment factor comprising a cellulose binding domain and the fibronectin‐like RGD attachment peptide. The technique used local thresholding, median filtering, and opening to separate and count cells on each image. Cell lines exhibited three different patterns of attachment to CBD/RGD, depending on whether it was immobilized on polystyrene or cellulose acetate. Vero, COS, HFF, 3T3, 293, and U373 cells attached well to CBD/RGD immobilized on polystyrene or cellulose acetate. CHO, MRC‐5, and HEp‐2 cells attached to CBD/RGD immobilized on polystyrene, but not to CBD/RGD immobilized on cellulose acetate. BHK and L cells failed to attach to CBD/RGD immobilized on either polystyrene or cellulose acetate. The attachment of many cell lines to CBD/RGD was comparable with attachment of these cells to fibronectin. © 1995 John Wiley & Sons, Inc.
Cartilage production by rabbit articular chondrocytes on polyglycolic acid scaffolds in a closed bioreactor system
Authors: Dunkelman Noushin S. , Zimber Michael P. , LeBaron Richard G. , Pavelec Rebecca , Kwan Michael , Purchio A. F. 
Published: December 2004

AbstractRabbit articular chondrocytes were seeded onto three‐dimensional polyglycolic acid (PGA) scaffolds and placed into a closed bioreactor system. After 4 weeks of growth, meshes were examined for cartilage formation. Gross examination revealed solid, glistening material that had the appearance of cartilaginous tissue. Histologic examination revealed cell growth and deposition of extracellular matrix throughout the mesh with a less dense central core. Alcian blue and Safranin 0 staining showed deposition of glycosaminoglycans (GAGs). Immunostaining showed positive reactivity for type II collagen and chondroitin sulfate and no reactivity for type I collagen. Biochemical analysis showed collagen and GAG values to be 15% and 25% dry weight, respectively. Our results indicate that this type of system compares well with those previously described and should be useful for producing cartilage for evaluation in a clinical setting. © 1995 John Wiley & Sons, Inc.
Hydrodynamic effects on BHK cells grown as suspended natural aggregates
Authors: Moreira José L. , Alves Paula M. , Aunins John G. , Carrondo Manuel J. T. 
Published: December 2004

AbstractBaby hamster kidney (BHK) cell aggregates grown in stirred vessels with different working volumes and impeller sizes were characterized. Using batch cultures, the range of agitation rates studied (25–100 rpm) led to aggregates with maximum sizes of 150 μm. Necrotic centers were not observed and cell specific productivity was independent of aggregate size. High cell viability was found for both single and adherent cells without an increase in cell death when agitation rate was increased. The increase in agitation rate affected aggregates by reducing their size and increasing their concentration and cell concentration in aggregates, while increasing the fraction of free cells in suspension. The experimental relationship between aggregate size and power dissipation rate per unit of mass was close to −1/4, suggesting a correlation with a critical turbulence microscale; this was independent of vessel scale and impeller geometry over the range investigated. Viscous stresses in the viscous dissipation subrange (below Kolmogoroff eddies) appear to be responsible for aggregate breakage. Under intense agitation BHK cells grown in the absence of microcarriers existed as aggregates without cell damage, whereas cells grown on the surface of microcarriers were largely reduced. This is a clear advantage for scaleup purposes if aggregates are used as a natural immobilization system in stirred vessels. © 1995 John Wiley & Sons, Inc.
Kinetics and mass transfer for lactic acid recovered with anion exchange method in fermentation solution
Authors: Zihao Wang , Kefeng Zhao 
Published: December 2004

AbstractAn anion exchange method for lactic acid recovered from lactic acid–glucose solution in an ion‐exchange membrane‐based extractive fermentation system was examined. The exchange isotherms of anion exchange resins for lactic acid recovered were measured batchwise, and the exchange–desorption kinetics of lactic acid passing through the exchange column was investigated. The determined typical breakthrough and elution curves were measured and simulated by conventional mode. The mass transfer coefficients were identified by numberical method. The effects of the velocity of the fluid on the dynamics were studied. Aqueous NaOH solution was found to be the best solvent for elution. An experiment on anioun exchange from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the ion exchange system from a borth. The ion‐exchange mass‐transfer coefficient and efficiency from the fermentation broth is found to be lower when compared with aqueous solutions of pure lactic acid. The results show that the separation method with anion exchange resins may be used in the production of lactic acid by fermentation.© 1995 John Wiley & Sons, Inc.
Do organic solvents affect the catalytic properties of lipase? Intrinsic kinetic parameters of lipases in ester hydrolysis and formation in various organic solvents
Authors: van Tol J. Bert A. , Stevens Rob M. M. , Veldhuizen Willem J. , Jongejan Jaap A. , Duine Johannis A. 
Published: December 2004

AbstractWhen it is assumed that organic solvents do not interfere with the binding process nor with the catalytic mechanism, the contribution of substrate‐solvent interactions to enzyme kinetics can be accounted for by just replacing substrate concentrations in the equations by thermodynamic activities. It appears from the transformation that only the affinity parameters (Km, Ksp) are affected by this. Thus, in theory, the values of these corrected, intrinsic parameters (K, k) and the maximal rate (V1) should be equal for all media. This was tested for hydrolysis, transesterification, and esterification reactions catalyzed by pig pancreas lipase and Pseudomonas cepacia lipase in various organic solvents. Correction was carried out via experimentally determined activity coefficients for the substrates in these solvents or, if not feasible, from values in data bases. However, although the kinetic performances of each enzyme in the solvents became much more similar after correction, differences still remained. Analysis of the enzyme suspensions revealed massive particles, which explains the low activity of enzymes in organic solvents. However, no correlation was found between estimates of the amount of catalytically available enzyme (present at the surface of suspended particles or immobilized on beads) and the maximal rates observed. Moreover, the solvents had similar effects on the intrinsic parameters of suspended and immobilized enzyme. The possible causes for the effects of the solvents on the catalytic performance of the enzymes, remaining after correction for solvent‐substrate interactions and the amount of participating enzyme, are discussed with respect to the premises on which the correction method is based. © 1995 John Wiley & Sons, Inc.
Membrane‐attached biofilms for VOC wastewater treatment I: Novel in situ biofilm thickness measurement technique
Authors: dos Santos L. M. Freitas , Livingston A. G. 
Published: December 2004

AbstractThis article reports a novel nondisruptive technique for measuring the thicknesses of membrane‐attached biofilms in situ, using a single tube extractive membrane bioreactor (STEMB). The biodegradation of a toxic volatile organic compound (VOC) (1,2‐dichloroethane [DCE]) by Xanthobacter autotrophicus GJ10 has been used as a model system to develop the technique. The results give information on the biomass‐silicone rubber attachment phenomena, and on the development over time of biofilms growing on the silicone membrane, without disrupting operation. Experimental results are presented showing the evolution over time of biofilm thickness, and also the density of biofilms for four experimental runs. The hydrodynamic conditions on the biomedium side of the membrane were found to influence the initial attachment phenomena and subsequent biofilm growth. © 1995 John Wiley & Sons, Inc.
Kinetics of phenolic polymerization catalyzed by peroxidase in organic media
Authors: Xu Yue‐Ping , Huang Guo‐Lan , Yu Yao‐Ting 
Published: December 2004

AbstractPhenolic polymerization was carried out by enzymatic catalysis in organic media, and its kinetics was studied by using high‐pressure liquid chromatography (HPLC). Phenols and aromatic amines with electron‐withdrawing groups could hardly be polymerized by HRP catalysis, but phenols and aromatic amines with electron‐donating groups could easily be polymerized. The reaction rate of either the para‐substituted substrate or meta‐substituted substrate was higher than that of ortho‐substituted substrate. When ortho‐position of hydroxy group of phenols was occupied by an electron‐donating group and if another electron‐donating group occupied para‐position of hydroxy group, the reaction rate increased. Horseradish peroxidase and lactoperoxidase could easily catalyze the polymerization, but chloroperoxidase and laccase failed to yield polymers. Metallic ions such as Mn2+, Fe2+, or Fe3+, and Cu2+ could poison horseradish peroxidase to various extents, but ions such as Co2+, Cd2+, Zn2+, and K+ were not found to inhibit the reaction. © 1995 John Wiley & Sons, Inc.
Production and properties of a bifunctional fusion protein that mediates attachment of vero cells to cellulosic matrices
Authors: Wierzba Andrew , Reichl Udo , Turner Robin F. B. , Warren R. Antony J. , Kilburn Douglas G. 
Published: December 2004

AbstractThe sequence Arg‐Gly‐Asp (RGD) in extracellular matrix proteins such as fibronectin, collagen, and laminin mediates cell attachment by interacting with proteins of the integrin family of cell surface receptors. A gene fusion encoding the RGD‐containing peptide, fused to the C‐terminus of a cellulose‐binding domain (CBD/RGD), was expressed in Escherichia coli. Cultures produced up to 50 mg of CBD/RGD per liter, most of which was extracellular. It was purified from the culture supernatant by affinity chromatography on cellulose. CBD/RGD promoted the attachment of green monkey Vero cells to polystyrene and cellulose acetate. Attachment was inhibited by small synthetic peptides containing the RGD sequence. CBD/RGD was as effective as collagen in promoting the attachment of Vero cells to Cellsnow™ microcarriers. © 1995 John Wiley & Sons, Inc.
Fluxes of carbon, phosphorylation, and redox intermediates during growth of saccharomyces cerevisiae on different carbon sources
Authors: Cortassa Sonia , Aon Juan C. , Aon Miguel A. 
Published: December 2004

AbstractIn the present work we develop a method for estimating anabolic fluxes when yeast are growing on various carbon substrates (glucose, glycerol, lactate, pyruvate, acetate, or ethanol) in minimal medium. Fluxes through the central amphibolic pathways were calculated from the product of the total required amount of a specified carbon intermediate times the growth rate. The required amount of each carbon intermediate was estimated from the experimentally determined macromolecular composition of cells grown in each carbon source and the monomer composition of macromolecules.Substrates sharing most metabolic pathways such as ethanol and acetate, despite changes in the macromolecular composition, namely carbohydrate content (34% ± 1 and 21% ± 3, respectively), did not show large variations in the overall fluxes through the main amphibolic pathways. For instance, in order to supply anabolic precursors to sustain growth rates in the range of 0.16/h to 0.205/h, similar large fluxes through Acetyl CoA synthase were required by acetate (4.2 mmol/hr g dw) or ethanol (5.2 mmol/h g dw).The Vmax activities of key enzymes of the main amphibolic pathways measured in permeabilized yeast cells allowed to confirm, qualitatively, the operation of those pathways for all substrates and were consistent on most substrates with the estimated fluxes required to sustain growth.When ATP produced from oxidation of the NADH synthesized along with the key intermediary metabolites was taken into account, higher Y values (36 with respect to 24 g dw/mol ATP) were obtained for glucose. The same result was obtained for glycerol, ethanol, and acetate. A yield index (YI) was defined as the ratio of the theoretically estimated substrate flux required to sustain a given growth rate over the experimentally measured flux of substrate consumption. Comparison of Yl between growth on various carbon sources led us to conclude that ethanol (Yl = 0.84), acetate (Yl = 0.77), and lactate (Yl = 0.77) displayed the most efficient use of substrate for biomass production. For the other substrates, the Yl decayed in the following order: pyruvate > glycerol > glucose.An improvement of the quantitative understanding of yeast metabolism, energetics, and physiology is provided by the present analysis. The methodology proposed can be applied to other eukaryotic organisms of known chemical composition. © 1995 John Wiley & Sons, Inc.
Effect of yeast extract on growth kinetics during aerobic biodegradation of chlorobenzoic acids
Authors: Armenante Piero M. , Fava Fabio , Kafkewitz David 
Published: December 2004

AbstractThe Monod or Andrews kinetic parameters describing the growth of Pseudomonas sp. CPE2 strain on 2,5‐dich!orobenzoic acid and 2‐chlorobenzoic acid, and Al‐caligenes sp. CPE3 strain on 3,4‐dichlorobenzoic acid, 4‐chlorobenzoic acid, and 3‐chlorobenzoic acid were determined from batch and continuous growth experiments conducted in the presence or absence of yeast extract (50 mg/L). Strain CPE2 displayed inhibitory growth kinetics in the absence of yeast extract and a noninhibitory kinetics in the presence of yeast extract. Similar results were obtained for CPE3. The presence of yeast extract also resulted in a significant increase in the affinity of the strains for the chlorobenzoic acids they degraded. © 1995 John Wiley & Sons, Inc.