bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonisotropic Scattering Model for Estimation of Light Absorption Rates in a Suspension Culture of Coffea arabica Cells
Authors: Kurata Hiroyuki , Furusaki Shintaro
Published: March 2005

A nonisotropic scattering model is proposed to estimate the light absorption rates in a heterogeneous photoreactor containing plant cells of Coffea arabica and is compared with an isotropic scattering model. In order to determine the directions of noniso‐tropically scattered light, optical theorems (geometrical optics and wave optics) are applied to light scattering caused by a homogeneous and perfect sphere. Two parameters, relative refractive index and attenuation coefficient, are used to characterize the ideal sphere. The primary feature of this model is that various phenomena of light scattering and absorption can be simulated by the combination of the two parameters. A measuring system composed of parallel plates was developed for evaluating the model. The nonisotropic scattering model was successfully applied to the heterogeneous reactor with the cultured plant cells.
Comparison of Metabolism of Hybridoma Cells Cultured in Media Supplemented with Whey or Fetal Calf Serum
Authors: Legrand C. , Capiaumont J. , Belleville F. , Nabet P.
Published: March 2005

The effects of industrial whey on cell physiology were studied in a repeated fed‐harvest mode using free‐suspended murine hybridoma cells. After several days of culture in medium containing 9% whey and 1% fetal calf serum (FCS), cell growth and viability, carbohydrate, amino acid, energy metabolism, and antibody production rates were investigated. Differences were found between cells cultured in whey medium and those cultured in conventional FCS medium. The cell growth obtained in medium supplemented with fresh whey was similar to that obtained in FCS medium. The viability showed an increase for hybridoma cells cultured in whey medium. Glucose consumption rates were similar, whereas the lactate production rate was higher in whey medium. The metabolic uptake rates of glutamine and ammonia increased in whey medium. More alanine, glutamate, glycine, and proline were produced; their production partly came from glutamine and lactate. The consumption rates of branched amino acids changed little; their utilization was higher in whey medium. Finally, antibody productivity was increased about 20% for cells cultured in medium containing whey.
Development of Scale‐Down Techniques for Investigation of Recombinant Escherichia coli Fermentations: Acid Metabolites in Shake Flasks and Stirred Bioreactors
Authors: Dahlgren Mary Ellen , Powell Alan L. , Greasham Randolph L. , George Hugh A.
Published: March 2005

We have developed shake‐flask screening conditions that are predictive of specific expression of the chimeric toxin, TGFα‐PE40, by recombinant Escherichia coli JM109 in stirred bioreactors. When a nutrient‐rich stirred bioreactor medium was used in shake flasks, neither the extent of growth nor the specific level of recombinant protein expression duplicated the performance in stirred bioreactor fermentations. Incomplete oxidation of glucose and concomitant accumulation of organic acid metabolites, as well as oxygen limitation and lack of pH control, were examined as contributors to the poorer performance in the flask. The medium buffering capacity, initial glucose level, and flask aeration were evaluated to establish the limits of “scale‐down” conditions for expression both in a complex nutrient medium (M101) similar to that used in stirred bioreactors and in a defined (FM) medium. Acid metabolites and ethanol were measured as indicators of carbon flow from glucose as well as indirect indicators of oxygen limitation. For the complex M101 medium, optimal shake‐flask performance in 250‐mL, nonbaffled flasks at 37°C occurred with 0.3X medium strength, supplementation with 0.3 M HEPES buffer (pH 7.5), and 10 mL of medium per flask. Cultures grown under these conditions produced a maximum density of 3.6 g of dry cell weight/L (as estimated by absorbance measurements at 600 nm) and maintained a pH near neutrality. Additionally, metabolite markers of anaerobic or microaerobic conditions, such as ethanol, lactate, and pyruvate, were not detected, and specific expression of TGFα‐PE40 was comparable to stirred bioreactors induced for expression at various biomass levels. When culture parameters were controlled within these limits, similar results were also observed in the defined FM medium.
Synthesis of β‐Ionone in an Aldehyde/Xanthine Oxidase/β‐Carotene System Involving Free Radical Formation
Authors: Bosser Aurélie , Belin Jean Marc
Published: March 2005

The enzymic cooxidation of β‐carotene (BC) by xanthine oxidase (XO) in aqueous solutions leads to β‐ionone (BI) and derivatives: epoxy‐β‐ionone (EPBI), dihydroactinidiolide, β‐cyclocitral, pseudoionone, etc. We demonstrate, in this article, that this is due to free radical (R⋅) formation during the first hour of stirring and the use of aldehydes as substrate. The bleaching of BC does not occur when the common substrate of XO, xanthine, is used; this proves that the superoxide anion O2⋅‐ alone is not active on BC. BI formation in this case is not observed.
Effect of Glucose on the Expression Parameters of Recombinant Protein in Escherichia coli during Batch Growth in Complex Medium
Authors: Li Xiaoli , Taylor Kenneth B.
Published: March 2005

The expression parameters were determined at different phases of batch growth of Escherichia coli JM101/pYEJ001 in complex medium and at different conditions of glucose addition. Thus the plasmid content, the RNA content, the RNA synthesis rate, the specific recombinant mRNA content, the specific recombinant mRNA synthesis rate, the recombinant chloramphenicol acetyltransferase content, and the overall protein synthesis rate were determined during growth with no glucose, with initial glucose, with glucose feeding during stationary phase, and with initial glucose plus glucose feeding during stationary phase. The results show that the specific rate of total RNA synthesis was enhanced in the presence of glucose at both exponential and stationary phases, while recombinant mRNA synthesis was enhanced only at stationary phase by glucose feeding. However, the steady‐state level of the recombinant mRNA was not changed under the same conditions. In addition, although the overall protein synthesis rate at exponential phase was enhanced in the presence of glucose, the specific recombinant protein level was unaffected. The specific synthesis rate of recombinant mRNA varied inversely with the plasmid content during exponential and stationary phases. Furthermore, changes in the specific activity of the recombinant protein were not correlated with either the changes in the specific synthesis rate of the recombinant mRNA or the overall protein synthesis rate. Therefore, the specific activity of the recombinant protein is not universally limited by its gene transcription rate or the overall protein synthesis capacity.
Carbon Flux Distributions at the Pyruvate Branch Point in Corynebacterium glutamicum during Lysine Overproduction
Authors: Vallino Joseph J. , Stephanopoulos Gregory
Published: March 2005

In order to achieve the theoretical maximum yield of lysine from glucose (75% molar), flux partitioning at principal branch points (glucose 6‐phosphate, phosphoenolpyruvate, and pyruvate) in the primary metabolic network of Corynebacterium glutamicum must be significantly altered from that observed during balanced growth, so that lysine precursors are synthesized in optimal stoichiometric ratios. In this article, we employ flux analysis, which provides a snapshot of metabolic flux distributions from extracellular measurements, in conjunction with two metabolic perturbations of the pyruvate dehydrogenase complex (PDC) to examine the possibility that flux partitioning at the pyruvate (Pyr) branch point (i. e., pyruvate availability) limits lysine yield. The two perturbation experiments involved (1) isolation and flux analysis of a PDC‐attenuated mutant of C. glutamicum and (2) flux analysis following the addition of fluoropyruvate (FP) to a standard fermentation during the initial period of lysine overproduction. No significant alteration in flux partition was observed at any of the three principal nodes in the PDC‐attenuated strain. However, the PDC mutation did cause a 70% uniform decrease in carbon flow throughout the network, which indicates that the lysine yield is not limited solely by a weakly rigid Pyr branch point. The addition of FP did not affect the lysine synthesis rate, but did temporarily redirect carbon flow away from the TCA cycle toward pyruvate excretion, which further confirms that the lysine yield is not pyruvate‐limited and that the Pyr branch point is not weakly rigid.
Microbial Oxidation of Hydrogen Sulfide in a Pilot‐Scale Bubble Column
Authors: Sublette Kerry L. , Hesketh Robert P. , Hasan Saleem
Published: March 2005

Thiobacillus denitrifians is a chemoautotroph and a facultatively anaerobic bacterium that can use reduced sulfur compounds as energy sources with oxidation to sulfate. Under anoxic conditions, nitrate may serve as a terminal electron acceptor with reduction to elemental nitrogen. T. denitrificans has previously been shown to remove hydrogen sulfide from sour gases under both aerobic and anoxic conditions. Hydrogen sulfide concentrations were reduced from 10 000 ppmv to undetectable levels with 1–2 s of gas‐liquid contact time in bench‐scale fermentors. The oxidation product, sulfate, accumulated in the liquid phase of the culture medium. Flocculated T. denitrificans has now been used to remove hydrogen sulfide (up to 1500 ppmv) from a sour gas in a 0.5‐m3 pilot‐scale bubble column. The bubble column was operated for 7 weeks under aerobic conditions, with gas feeds of air and hydrogen sulfide in nitrogen. Up to 97% removal of hydrogen sulfide was observed with complete oxidation to sulfate, which accumulated in the reactor medium. Limitations in H2S removal were due to mass transfer and not the microbiology of the system. More complete H2S removal can be accomplished by increasing gas‐liquid contact in a single reactor or using two bubble columns in series.
Block Methacrylic Polyampholytes as Protein Displacers in Ion‐Exchange Chromatography
Authors: Patrickios C. S. , Gadam S. D. , Cramer S. M. , Hertler W. R. , Hatton T. A.
Published: March 2005

Low molecular weight methacrylic triblock copolymers bearing a block of negatively charged (adsorbing) residues, a sequence of positively charged (repelling) units, and a middle neutral hydrophobic block were utilized successfully in anion‐exchange displacement chromatography for the resolution of a crude mixture of/β‐lactoglobulins into the A and B isoforms. Owing to their low molecular mass and ampholytic nature, these novel displacers possess the attractive process‐scale features of easy column regeneration and polymer recycling.
Evaluation of the Cd, Cu, and Zn Biosorption in Two‐Metal Systems Using an Algal Biosorbent
Authors: De Carvalho R. P. , Chong K.‐H. , Volesky B.
Published: March 2005

The equilibrium sorption capacity of the formaldehyde‐cross‐linked brown seaweed Ascophyllum nodosum biomass was studied using two‐metal systems comprising either (Cu + Zn), (Cu + Cd), or (Zn + Cd). Three‐dimensional sorption isotherm surfaces were used in the evaluation of sorption performance, replacing simple isotherm curves. While each of the metals tested can inhibit the sorption of the others, at low total residual metal concentrations the total metal sorption uptake increases. At higher total metal concentrations, the total metal sorption uptake either remains constant, or there may be a slight decrease compared to single‐metal uptakes. This is an indication of a mutual interference in the sorption uptake of the two metals tested in each system.
Biomass Estimation in Plant Cell Cultures: A Neural Network Approach
Authors: Albiol Joan , Campmajó Carles , Casas Carles , Poch Manel
Published: March 2005

The special characteristics of plant cell cultures make it difficult to use conventional analytical techniques for on‐line biomass monitoring. Meanwhile, promising results have been obtained using mathematical models and recursive estimation algorithms. However, in this case, additional experimental effort is necessary to obtain a reasonable description of the process. Recently, techniques using more empirical approaches have been proposed to describe complex processes, minimizing the experimental work needed for their application. In this paper, we report on the use of artificial neural networks to monitor biomass evolution in plant cell cultures. The results obtained with a three‐layered network are presented. Method requirements and capabilities are compared with the method based on the extended Kalman filter used in previous work.
Cell Damage and Oxygen Mass Transfer during Cultivation of Nicotiana tabacum in a Stirred‐Tank Bioreactor
Authors: Ho Chung ‐Han , Henderson Kelley A. , Rorrer Gregory L.
Published: March 2005

Cell damage and oxygen mass transfer were investigated during the batch culture of Nicotiana tabacum (tobacco) cells in a 3‐L Applikon stirred‐tank bioreactor equipped with a marine‐blade impeller. Total cell density, % culture viability, viable cell density, and kLa in the culture were measured over a 24‐day cultivation period at impeller speeds of 100–325 rpm under a fixed air flow of 0.43 wm and a temperature of 27 °C. The maximum total biomass density decreased from 11.8 g of dry cell weight (DCW)/L at 100 rpm to 8.6 g of DCW/L at 325 rpm. The net specific biomass production rate of viable cells (μv) during the exponential phase and the viable cell death rate (kd) during the stationary phase were estimated from semilog plots of viable cell density vs cultivation time. Values for μv decreased from 0.175 to 0.077 day−1 whereas values for kd increased from 0.042 to 0.109 day−1 with increasing impeller tip speed (from 24 to 77 cm/s), clearly showing that increasing agitation intensity increased the rate of cell damage. The effect was most pronounced at tip speeds of 24–60 cm/s. With respect to oxygen mass transfer, culture kLa values were about 10–20% higher than their corresponding initial kLa° values, but as the cell density increased, the values for kLa ultimately decreased. Despite the reduction in oxygen mass transfer rates, at impeller speeds of 100–325 rpm and an aeration rate of 0.43 wm, oxygen starvation was not observed. Therefore, the reduction in biomass productivity can be attributed to cell damage by hydrodynamic forces and not by inadequate oxygen mass transfer.
Microbial Reduction of Sulfur Dioxide with Anaerobically Digested Municipal Sewage Biosolids as Electron Donors
Authors: Selvaraj Punjai T. , Sublette Kerry L.
Published: March 2005

A concentrated stream of sulfur dioxide (SO2) is produced by regeneration of the sorbent in certain new regenerable processes for the desulfurization of flue gas. We have previously proposed that this SO2 can be converted to elemental sulfur for disposal or byproduct recovery using a microbial/Claus process. In this process, two‐thirds of the SO2‐reducing gas stream would be contacted with a mixed culture containing sulfate‐reducing bacteria (SRB), where SO2 would act as an electron acceptor with reduction to hydrogen sulfide (H2S). This H2S could then be recombined with the remaining SO2 and sent to a Claus unit to produce elemental sulfur. The sulfate‐reducing bacterium, Desulfouibrio desulfuricans, has been immobilized by coculture with flocforming heterotrophs from an anaerobic digester, resulting in a SO2‐reducing floc that may be collected from the effluent of a continuous reactor for recycle by gravity sedimentation. The carbon and energy source for these cultures was anaerobically digested municipal sewage solids. The maximum specific activity for SO2 reduction in these cultures, in terms of dry weight of D. desulfuricans biomass, was 9.1 mmol of SO2/h. g. The stoichiometry with respect to the electron donor was 15.5 mg of soluble COD/mmol of SO2 reduced.
Biotreatment of Refinery Spent Sulfidic Caustics
Authors: Rajganesh B. , Sublette K. L. , Camp C. , Richardson M. R.
Published: March 2005

Caustics are used in petroleum refining to remove hydrogen sulfide from various hydrocarbon streams. Spent sulfidic caustics from two Conoco refineries have been successfully biotreated on a bench scale, resulting in neutralization and removal of active sulfides. Sulfides were completely oxidized to sulfate by Thiobacillus denitrificans. Microbial oxidation of sulfide produced acid, which at least partially neutralized the caustic.
Hydrodynamics and Mass Transfer in a Four‐Phase External Loop Air Lift Bioreactor
Authors: Sajc Lidija , Obradovic Bojana , Vukovic Dragoljub , Bugarski Branko , Grubisic Dragan , Vunjak‐Novakovic Gordana
Published: March 2005

An external loop air lift reactor (ELALR) was developed and designed for continuous production and extraction of extracellular secondary metabolites by immobilized Frangula alnus Mill. plant cells. This system was considered as a four‐phase system, with dispersed gas, nonaqueous liquid solvent, and calcium alginate particles in water or Murashige and Skoog medium. Analysis of the four‐phase ELALR revealed the influence of gas, solvent, calcium alginate particles and MS medium composition on gas and solvent holdup, liquid circulation velocity, mixing in aqueous liquid phase, and mass transfer coefficients of oxygen and plant cell product. It was shown that the gas holdup appears to be the principal variable determining the properties of the four‐phase system. An unified correlation for the gas holdup, based on drift flux flow in a three‐phase system, has been extended to the four‐phase system. Bubble size and bubble size distribution observed in the bubbly flow regime were the same in water as in the MS medium system (Sauter mean diameter 2.5 mm). Consequently, gas holdup and all related parameters, such as liquid circulation velocity, oxygen mass transfer coefficient, and axial liquid dispersion in MS medium, were similar to those in water for the four‐phase system.
Continuous Enantioselective Transesterification in Organic Solvents. Use of Suspended Lipase Preparations in a Microfiltration Membrane Reactor
Authors: Indlekofer Michael , Funke Marcus , Claassen Wolfgang , Reuss Matthias
Published: March 2005

A continuously stirred tank reactor equipped with a microfiltration membrane unit for effective retention of solid enzyme particles in organic solvent systems was constructed. A microfiltration membrane with pore size 0.1 μm based on a polypropylene matrice was used for enzyme retention and showed no loss of performance or denaturation by the organic solvent. The stereoselective transesterification reaction of (±)‐trans‐sobrerol with vinyl acetate as both acyl donor and solvent was chosen as a model system. Lipase PS from Pseudomonas sp. was used in its native form without further modification steps and remained active and highly stereoselective at 50 °C when applied to the reaction system for about 600 h of continuous operation. (‐‐)‐(1S,5R)‐sobrerolacetate and (+)‐(1R,5S)‐sobrerol could be obtained in the reactor outlet stream at approximately 48% conversion with enantiomeric excesses eeP ≈︁ 92% and eeS≈︁ 80%, respectively. Furthermore, theoretical kinetic studies showed that limitations in enantiomeric purity due to the characteristics of an ideal mixed tank may be sufficiently overcome by designing a simple two‐stage process.
Effect of Cell Concentration on the Kinetics of Whole‐Cell Enzyme Entrapped within Calcium Alginate
Authors: Lee Wen‐Chien , Lee Ru ‐Yue , Ruaan Ruoh ‐Chyu
Published: March 2005

A method for determining the kinetics of whole‐cell enzymes entrapped within calcium alginate gel beads is presented. Diffusivities of the substrate and the product and kinetic parameters, i.e., the Michaelis constant and the maximum velocity, could be estimated by fitting experimental data to a proposed mathematical model. Immobilized cell concentration was found to be the main factor causing a decrease in maximum velocity. The influence of cell concentration in the gel beads on the variation in the maximum velocity could be isolated from the effect of cell concentration on diffusional limitation and evaluated separately. The whole‐cell enzymes became partially difficult to access by substrate when the cell population increased. The loss of enzyme accessibility resulted in a decrease in the maximum velocity and apparent initial velocity. This phenomenon of the maximum velocity varying with immobilized cell concentration has not been reported in the literature.
Cell Growth and Monoclonal Antibody Production in the Presence of Antigen and Serum
Authors: Dandulakis Gregory , Herr John C. , Kirwan Donald J.
Published: March 2005

The impact that the continuous presence in the fermentation broth of the cognate antigen has on the serum‐supplemented hybridoma cell cultures was investigated. Both soluble and immobilized antigen at various concentrations was applied. The cell line (ATCC TIB191) was cultured in a serum‐supplemented PFHM‐II medium in T‐flasks. Sepharose gel beads provided the immobilization matrix, and bovine γ‐globulin was the carrier protein upon which the antigen, picric acid, was conjugated. Produced antibody, after elution from the beads by displacement with free picric acid, was measured with an ELISA. Soluble antigen—carrier protein conjugates showed no effect on the cultures, but the immobilized antigen had a strong influence on them. Cell growth rate and total antibody production decreased as the amount of immobilized antigen increased from 16:10 (units are in (mol of Ag/mol of carrier):(mg of carrier/mL of beads) to 36:40. Most importantly, the specific antibody production rate switched from growth phase‐independent behavior in the antigen‐free cultures to growth phase‐dependent behavior in the immobilized antigen cultures. Furthermore, during the early stationary phase of the cultures with immobilized antigen, the specific antibody production was 20–100% higher relative to the production rate in antigen‐free cultures. This increased specific antibody production rate would be particularly useful in increasing the volumetric productivity of perfusion‐type bioreactors for hybridoma cell cultures.
Monitoring of the Biological Nutrient Removal Process by an On‐Line NAD(P)H Fluorometer
Authors: Ju Lu ‐Kwang , Xin Yang  , Lee Jaw F. , Armiger William B.
Published: March 2005

An on‐line NAD(P)H fluorometer has been used to investigate the fluorescence profile of a simulated anaerobic/anoxic/oxic biological nutrient removal (BNR) process and its dependency on operating parameters, such as the concentrations of organic substrate (acetate) and activated sludge. As expected from the different rates of NAD‐(P)H oxidation at different stages, the order of fluorescence levels was found to be anaerobic > anoxic > oxic. The effects of the acetate and sludge concentrations were observed most clearly at the anoxic stage: an increase in either concentration led to faster recovery of fluorescence from the drop caused by NO3− addition. A higher acetate concentration also resulted in a more significant, continuous rise in fluorescence, corresponding well with the enhanced PO43− release, at the anaerobic stage and a slower initial fluorescence decrease at the oxic stage, indicating the dependency of the decrease on substrate availability. The ratio of the two fluorescence drops caused by NO3− addition and aeration, Δ1/Δ2, obtained with the plant's sludge was found to be 0.7 × 0.1, which is similar to those of pure nitrate‐respiring cultures (e.g., Pseudomonas aeruginosa and Escherichia coli). The dominant majority of nonnitrifiers in the sludge therefore are capable of nitrate respiration, and the nitrifiers either contribute little to the overall fluorescence or perform nitrate respiration as the rest of the sludge population.
Alteration of Hybridoma Viability and Antibody Secretion in Transfectomas with Inducible Overexpression of Protein Disulfide Isomerase
Authors: Kitchin Kirsten , Flickinger Michael C.
Published: March 2005

Monoclonal antibody (mAb)‐secreting transfectomas with dexamethasone inducible expression of the mammalian endoplasmic reticulum foldase and chaperone protein disulfide isomerase (PDI, ERp59) were generated from the murine 9.2.27 hybridoma in order to obtainin vivoevidence of whether alteration of the level of PDI, believed to be involved in immunoglobulin (Ig) assembly, results in alteration of mAb secretion kinetics. Using an RNase refolding assay, the specific activity of endogenous PDI in the 9.2.27 hybridoma was found to be constant during batch growth. An expression vector for glucocorticoid‐inducible overexpression of PDI, pMMTVPDI, was constructed from pMAMneo using a rat PDI cDNA. Cell lysates of stable transfectomas contained 2–4‐fold higher levels of PDI mRNA and increased levels of PDI protein, detected by immunoblotting, following induction with 0.1μM dexamethasone. Monoclonal antibody secretion kinetics were evaluated in 12.5 mL shake flasks, a 100 mL spinner, and a 1 L aerated batch reactor. A transfectoma was found with altered mAb secretion kinetics during cell growth following dexamethasone induction of PDI overexpression. Specific mAb secretion rate was not significantly increased following dexamethasone induction; however, hybridoma viability was sustained longer during the stationary phase of cell growth and hence total antibody yield was increased in comparison to the parent 9.2.27 hybridoma.
Simulation of Diauxic Production of Cephalosporin C by Cephalosporium acremonium: Lag Model for Fed‐Batch Fermentation
Authors: Basak Subir , Velayudhan Ajoy , Ladisch Michael R.
Published: March 2005

We extend a previously reported model (Chu, W. B.; Constantinides, A. Biotechnol. Bioeng. 1988, 32, 277–288) for the batch fermentation of cephalosporin C under the diauxic growth of Cephalosporium acremonium on glucose and sucrose to a fed‐batch system. For this purpose, a novel lag model is proposed for diauxie, which has two functional forms, each embodying the dependence of lag on total cell mass and secondary substrate concentration. This lag model is applicable for batch simulations for arbitrary initial glucose and sucrose concentrations. We used the previously reported batch data to perform locally optimized fed‐batch simulations. When applied to fed‐batch fermentations, multiple lag times were accounted for. These studies showed that fed‐batch fermentations (under the restriction that cell mass concentration did not exceed 25 g/L) could be more productive than simple batch runs. A representative result for a glucose‐pulse fed‐batch run at optimal cephalosporin production is a productivity of 4.22 mg of cephalosporin C/(L·h) and a production yield of 9.25 mg of cephalosporin C/g of total sugar used.
Induction of Cytochrome P‐4501A1 Activity in Response to Sublethal Stresses in Microcarrier‐Attached Hep G2 Cells
Authors: Mufti Naheed A. , Shuler Michael L.
Published: March 2005

Cell damage for cells grown on microcarriers in suspension is a critical problem for scale‐up of microcarrier reactors. In order to study cell damage as a mechanistic process, a cellular response that is more sensitive than changes in growth and death rates and would be more closely related to cell regulatory mechanisms would be advantageous. We have observed the induction of a specific cytochrome P‐450 monooxygenase, P‐450IA1 (CYP1A1), to be a sensitive method for assessing the response of microcarrier‐attached Hep G2 cells to stress resulting from hydrodynamic shear and oxygen deprivation. The kinetics of induction and amount of CYP1Al formed in response to subtle shear stress, moderate shear, and hypoxia are described. Increased stress results in increased CYP1A1 formation.
Continuous Fermentation and Stripping of Ethanol
Authors: Taylor Frank , Kurantz Michael J. , Goldberg Neil , Craig James C.
Published: March 2005

Recycling the contents of a continuous fermentor through a stripping column is proposed as a means of reducing product inhibition and lowering the cost of fuel ethanol production. A 2‐L fermentor and 10‐cm packed column were continuously operated for 150 days without contamination. Some fouling of the packing with attached yeast cells was observed which partially blocked the column. Cell yield was lower than in a simple continuous fermentor. Complete conversion of 200 g/L glucose feed and 90% conversion of 600 g/L glucose feed were achieved. Data were analyzed by computerized process simulation. Cost analysis indicated that, with heat recovery to reduce heating and cooling costs, the continuous fermentor/stripper is possibly a lower‐cost alternative to conventional fermentation and distillation.
Volume changes of Vatnajökull ice cap, Iceland, due to surface mass balance, ice flow, and subglacial melting at geothermal areas
Authors: Magnússon Eyjólfur , Björnsson Helgi , Dall Jørgen , Pálsson Finnur
Published: March 2005

We present observed changes in the geometry of western Vatnajökull over a period of about ten years which are caused by the surface mass balance, ice flow (both during surges and quiescent periods), and basal melting due to geothermal and volcanic activity. Comparison of two digital elevation models shows that from 1985 to 1998 the outlet glaciers have lost 14 ± 5 km3, on the average 1 m yr−1 evenly distributed over the area of 1360 km2. However, the marginal areas of four outlets have gained up to 80 m in elevation and the uppermost parts have subsided similarly during surges. Altogether 26 ± 3 km3 were transported from the accumulation areas to the ablation areas of which 19 ± 3 km3 are attributed to surges. Comparison of DEM's from August 1997 and August 1998 revealed 10 ice cauldrons produced by subglacial geothermal activity, of which some were previously unknown.
Aerosol remote sensing from POLDER/ADEOS over the ocean: Improved retrieval using a nonspherical particle model
Authors: Herman M. , Deuzé J.‐L. , Marchand A. , Roger B. , Lallart P.
Published: March 2005

The properties of the aerosols over the ocean are re‐investigated by using the observations of the Polarization and Directionality of the Earth's Reflectance (POLDER) wide field of view imaging spectroradiometer developed by the Centre National d'Etudes Spatiales (CNES) and operated aboard the Japanese heliosynchronous Advanced Earth Observation Satellite (ADEOS) platform from 30 October 1996 to 30 June 1997. The measurement analysis leads us to assume that aerosols consist of particles with a bimodal size distributions, in which the large particle mode generally consists of nonspherical particles. In all observations where there is evidence for the occurrence of nonspherical particles from the spectral, directional, and polarization characteristics of the solar radiation scattered by the aerosols, the average aerosol scattering matrix for irregular particles derived recently by Volten et al. (2001) from laboratory measurements proves to provide a very efficient model of these particles.
Hydrothermal systems on Europa
Authors: Lowell Robert P. , DuBose Myesha
Published: March 2005

We estimate the global hydrothermal heat transport on Europa by considering the range of heat generation resulting from tidal stresses and radiogenic heat production within Europa's rocky sub‐ocean lithosphere. We show that if factors controlling tidally generated heat on Europa are similar to those on Io, global hydrothermal heat output and its high‐temperature component may exceed that on Earth. On the individual system scale, however, the low acceleration of gravity on Europa indicates that individual hydrothermal plumes are relatively weak. Such weak hydrothermal plumes are not likely to result in melt through events, which have been hypothesized to form surface features such as Conamara Chaos. Studies of concentrated hydrothermal activity and the resulting interacting plumes are needed to address the possible impact of hydrothermal activity on Europa's ice sheet.
Porphyrin-substrate binding to murine ferrochelatase: effect on the thermal stability of the enzyme
Authors: FRANCO Ricardo , BAI Guangyue , PROSINECKI Vesna , ABRUNHOSA Filipa , FERREIRA Gloria C. , BASTOS Margarida
Published: March 2005

Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the haem biosynthetic pathway, catalyses the chelation of Fe(II) into the protoporphyrin IX ring. The energetics of the binding between murine ferrochelatase and mesoporphyrin were determined using isothermal titration calorimetry, which revealed a stoichiometry of one molecule of mesoporphyrin bound per protein monomer. The binding is strongly exothermic, with a large intrinsic enthalpy (ΔH=−97.1 kJ · mol−1), and is associated with the uptake of two protons from the buffer. This proton transfer suggests that hydrogen bonding between ferrochelatase and mesoporphyrin is a key factor in the thermodynamics of the binding reaction. Differential scanning calorimetry thermograms indicated a co-operative two-state denaturation process with a single transition temperature of 56 °C for wild-type murine ferrochelatase. An increase in the thermal stability of ferrochelatase is dependent upon mesoporphyrin binding. Similarly, murine ferrochelatase variants, in which the active site Glu-289 was replaced by either glutamine or alanine and, when purified, contained specifically-bound protoporphyrin, exhibited enhanced protein stability when compared with wild-type ferrochelatase. However, in contrast with the wild-type enzyme, the thermal denaturation of ferrochelatase variants was best described as a non-co-operative denaturation process.
Induction of human spermine oxidase SMO(PAOh1) is regulated at the levels of new mRNA synthesis, mRNA stabilization and newly synthesized protein
Authors: WANG Yanlin , HACKER Amy , MURRAY-STEWART Tracy , FLEISCHER Jennifer G. , WOSTER Patrick M. , CASERO Robert A.
Published: March 2005

The oxidation of polyamines induced by antitumour polyamine analogues has been associated with tumour response to specific agents. The human spermine oxidase, SMO(PAOh1), is one enzyme that may play a direct role in the cellular response to the antitumour polyamine analogues. In the present study, the induction of SMO(PAOh1) enzyme activity by CPENSpm [N1-ethyl-N11-(cyclopropyl)methyl-4,8,diazaundecane] is demonstrated to be a result of newly synthesized mRNA and protein. Inhibition of new RNA synthesis by actinomycin D inhibits both the appearance of SMO(PAOh1) mRNA and enzyme activity. Similarly, inhibition of newly synthesized protein with cycloheximide prevents analogue-induced enzyme activity. Half-life determinations indicate that stabilization of SMO(PAOh1) protein does not play a significant role in analogue-induced activity. However, half-life experiments using actinomycin D indicate that CPENSpm treatment not only increases mRNA expression, but also leads to a significant increase in mRNA half-life (17.1 and 8.8 h for CPENSpm-treated cells and control respectively). Using reporter constructs encompassing the SMO(PAOh1) promoter region, a 30–90% increase in transcription is observed after exposure to CPENSpm. The present results are consistent with the hypothesis that analogue-induced expression of SMO(PAOh1) is a result of increased transcription and stabilization of SMO(PAOh1) mRNA, leading to increased protein production and enzyme activity. These data indicate that the major level of control of SMO(PAOh1) expression in response to polyamine analogues exposure is at the level of mRNA.
Molecular dynamics of transient oil flows in nanopores. II. Density profiles and molecular structure for decane in carbon nanotubes
Authors: Supple S. , Quirke N.
Published: March 2005

We report molecular dynamics simulations of nanotubes imbibing decane at an oil/vapor interface at 300K. We find that the smallest (7,7) nanotubes imbibe extremely rapidly (⩽800m∕s), with the imbibition speed slowing as the tube’s radius increases. The density profiles of the imbibing fluid in the pores are analyzed as a function of time. We find that the imbibing liquid is well described by the advection-diffusion equation and present expressions for the density profiles (in x and t) of the imbibing fluid as a function of the adsorption energy and surface friction of the pore. In addition we have analyzed the molecular structure of the imbibed fluid in nanotubes and describe how molecular conformations change with nanotube radius and position in the pore. We are therefore able to provide a complete description of the imbibition of a wetting fluid, decane, for a wide range of nanopores.
Chaotic synchronization of coupled electron-wave systems with backward waves
Authors: Hramov Alexander E. , Koronovskii Alexey A. , Popov Pavel V. , Rempen Irene S.
Published: March 2005

The chaotic synchronization of two electron-wave media with interacting backward waves and cubic phase nonlinearity is investigated in the paper. To detect the chaotic synchronization regime we use a new approach, the so-called time scale synchronization [Chaos 14, 603–610 (2004)]. This approach is based on the consideration of the infinite set of chaotic signals’ phases introduced by means of continuous wavelet transform. The complex space–time dynamics of the active media and mechanisms of the time scale synchronization appearance are considered.
Ferrimagnetic Mn4N(111) layers grown on 6H-SiC(0001) and GaN(0001) by reactive molecular-beam epitaxy
Authors: Dhar S. , Brandt O. , Ploog K. H.
Published: March 2005

Epitaxial films of ferrimagnetic Mn4N(111) are grown directly on 6H-SiC(0001) substrates and GaN∕6H-SiC(0001) templates using reactive molecular-beam epitaxy. The films are free from secondary phases and exhibit the theoretical saturation magnetization of Mn4N.
Freeze-dried cultures as commercial legume inoculants
Authors: McLeod RW , Roughley RJ
Published: March 2005

Commercially produced freeze-dried cultures of Rhizobium have been tested for suitability when used directly as legume inoculants. They compared favourably with commercial peat cultures in the number of viable cells per culture and gave comparable nodulation in three field trials. They were less perishable than peat cultures particularly at high temperatures (37�C).
The dependence of wheat quality tests on protein level — a comparative study of some Australian varieties
Authors: Mullaly JV , Moss HJ
Published: March 2005

Six commonly used wheat quality tests – baking performance, water absorption, dough development time, Valorimeter number, extensibility, and resistance to extension – have been examined for their abilities to characterise and discriminate among wheat varieties. Twelve Australian varieties are considered over a wheat protein range of 7.5–14.5 per cent. The recovery of wheat protein in the flour was also examined for their of the varieties. Except for resistance to extension, the tests showed a positive linear relationship of test measurement to log protein per cent, so that varieties were characterised for each of these tests by a pair of constants, a and b, where a is the average varietal value of the test property at 11.0 per cent wheat protein and b the average change in its value 46 per unit change in log protein per cent. The tests differ markedly in the extent and manner in which varieties are discriminated, baking performance being the most striking, in that the varieties are separated in two dimensions-level of performance (a) and sensitivity of performance to changes of protein content (b). Farinograph measurements discriminate primarily in the dimension of level performance for water absorption most of the varieties have approximate the same b values, while for dough development time and Valorimeter number the b values are positive and linearly related to the a values. For extensibility, varieties differ widely in both their a and b values but no clear pattern emerges, while for resistance to extension only differences in level of response occur. In most cases, the tests clearly distinguish between the hard and so) varieties, and within these groups suggestions are made and specifications are described for variety quality standards.
Modeling interactions between fire and atmosphere in discrete element fuel beds
Authors: Linn Rodman , Winterkamp Judith , Colman Jonah J. , Edminster Carleton , Bailey John D.
Published: March 2005

In this text we describe an initial attempt to incorporate discrete porous element fuel beds into the coupled atmosphere–wildfire behavior model HIGRAD/FIRETEC. First we develop conceptual models for use in translating measured tree data (in this case a ponderosa pine forest) into discrete fuel elements. Then data collected at experimental sites near Flagstaff, Arizona are used to create a discontinuous canopy fuel representation in HIGRAD/FIRETEC. Four simulations are presented with different canopy and understory configurations as described in the text. The results are discussed in terms of the same two discrete locations within the canopy for each simulation. The canopy structure had significant effects on the balance between radiative and convective heating in driving the fire and indeed sometimes determined whether a specific tree burned or not. In our simulations the ground fuel density was the determining factor in the overall spread rate of the fire, even when the overstory was involved in the fire. This behavior is well known in the fire meteorology community. In the future, simulations of this type could help land managers to better understand the role of canopy and understory structure in determining fire behavior, and thus help them decide between the different thinning and fuel treatment strategies available to them.
The role of released moisture in the atmospheric dynamics associated with wildland fires
Authors: Potter Brian E.
Published: March 2005

Combustion of woody material produces and releases water, but the effects of this water on the atmospheric circulation created by a wildfire are rarely recognized, let alone understood. This paper presents observational data and basic physical arguments to support the hypothesis that this moisture can constitute a large portion of the total water content in a fire plume. Calculations demonstrate the effects this moisture could have on fire-driven atmospheric circulations, specifically updrafts and downdrafts, on time and space scales important for fire behavior and fire-fighter safety. This study should be considered exploratory; it does not prove the presence or importance of this moisture, but seeks to show that further study is needed to determine how much moisture a fire adds to the air, and whether that amount is or is not important.
Differential use of endoplasmic reticulum membrane for phagocytosis in J774 macrophages
Authors: Becker Thalia , Volchuk Allen , Rothman James E.
Published: March 2005

Sustained phagocytosis requires the continuous replacement of cell-surface membrane from intracellular sources. Depending on the nature of the engulfed particles, a variety of endocytic compartments have been demonstrated to contribute membranes needed for the formation of phagosomes. It has recently been reported that the endoplasmic reticulum (ER) can also fuse with the plasma membrane during phagocytosis [Gagnon, E., Duclos, S., Rondeau, C., Chevet, E., Cameron, P. H., Steele-Mortimer, O., Paiement, J., Bergeron, J. J. & Desjardins, M. (2002)Cell110, 119–131]. However, there is currently no known mechanistic basis for this fusion process to occur. Here we report that direct ER–plasma membrane fusion during phagocytosis requires the ER resident solubleN-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein ERS24/Sec22b and that J774-macrophages react toward the challenge of large (3.0-μm) but not small (0.8-μm) particles by triggering this fusion mechanism, allowing them to access the most abundant endogenous membrane source in the cell, the ER.
The protooncogeneMYCcan break B cell tolerance
Authors: Refaeli Yosef , Field Kenneth A. , Turner Brian C. , Trumpp Andreas , Bishop J. Michael
Published: March 2005

The protooncogeneMYChas been implicated in both the proliferation and programmed cell death of lymphoid cells, and in the genesis of lymphoid tumors. Here, we report that overexpression ofMYC, as found in many lymphomas, can break immune tolerance. Mice that would otherwise be tolerant to a transgenic autoantigen mounted an immune response to the antigen ifMYCwas vigorously expressed in the B cell lineage. The responsive B cells converted to an activated phenotype and produced copious amounts of autoantibody that engendered immune complex disease of the kidney.MYCwas required to both establish and maintain the breach of tolerance. These effects may be due to the ability ofMYCto serve as a surrogate for cytokines. We found that the gene could mimic the effects of cytokines on both B cell proliferation and survival and, indeed, was required for those effects. These findings demonstrate a critical role forMYCin the response of B cells to antigen and expand the potential contributions ofMYCto the genesis of lymphomas.
Homoserine and asparagine are host signals that trigger in planta expression of a pathogenesis gene inNectria haematococca
Authors: Yang Zhennai , Rogers Linda M. , Song Yuanda , Guo Wenjin , Kolattukudy P. E.
Published: March 2005

Some pathogenesis-related genes are expressed in fungi only when the pathogen is in the host, but the host signals that trigger these gene expressions have not been identified. VirulentNectria haematococcainfects pea plants and requires eitherpelA, which is induced by pectin, orpelD, which is induced onlyin planta. However, the host signal(s) that triggerpelD expression was unknown. Here we report the isolation of the host signals and identify homoserine and asparagine, two free amino acids found in uniquely high levels in pea seedlings, as thepelD-inducing signals.N. haematococcahas evolved a mechanism to sense the host tissue environment by using the high levels of two free amino acids in this plant, thereby triggering the expression ofpelD to assist the pathogenic process.
Alpha‐1 anti‐trypsin deficiency and Henoch‐Schönlein purpura associated with anti‐neutrophil cytoplasmic and anti‐endothelial cell antibodies of immunoglobulin‐A isotype
Authors: Patterson Cynthia C. , Jr Patrick Ross , Pope‐Harman Amy L. , Knight Deborah A. , Magro Cynthia M.
Published: March 2005

Abstract:  Alpha‐1 anti‐trypsin (A1AT) deficiency is an inherited enzyme deficiency that manifests with fatal lung and liver complications. In addition to pulmonary and hepatic involvement, the disease has also been linked to an increased incidence of vasculitic syndromes and autoimmune diseases, including Wegener's granulomatosis, microscopic polyarteritis nodosa and Henoch‐Schönlein purpura (HSP). HSP, a systemic, small‐vessel vasculitis syndrome, is characterized by a non‐thrombocytopaenic purpuric rash, arthralgia, abdominal pain and nephritis. Both A1AT deficiency and HSP have been associated with anti‐neutrophil cytoplasmic antibodies (ANCA) and anti‐endothelial cell antibodies (AECA). We report a case of a 40‐year‐old man with severe A1AT deficiency, who developed HSP associated with AECA, ANCA and anti‐phospholipid antibodies of the immunoglobulin‐A isotype.
Creep During Sintering of Porous Compacts
Authors: RAHAMAN M.N. , DE JONGHE L.C. , HSUEH C.H.
Published: March 2005

Creep during sintering of CdO powder compacts was studied in a loading dilatometer by applying a small, transient, uniaxial load to the compacts. After the load was removed, the axial shrinkage rate was lower, but the radial shrinkage rate was actually higher than that of a compact sintered under no load. This reduction in the axial shrinkage rate is more pronounced for longer transient loading times. The results provide further support for a mechanism of simultaneous creep and densification in which creep at constant volume occurs by diffusion‐controlled grain‐boundary sliding.