bluuebunny/crossref_metadata_2025_split huggingface dataset:
Removal of Hydrogen Sulfide by Chlorobium thiosulfatophilum in Immobilized‐Cell and Sulfur‐Settling Free‐Cell Recycle Reactors
Authors: Kim Byung Woo , Chang Ho Nam 
Published: March 2005

AbstractBioconversion of hydrogen sulfide to elementary sulfur by the photosynthetic bacterium Chlorobium thiosulfatophilum was studied in immobilized‐cell and sulfur‐settling free cell recycle reactors. The cells immobilized in strontium alginate beads excreted elementary sulfur and accumulated it as crystal in the bead matrices, which made it possible that the reactor broth remained clear and the light penetrated the reactor deeper than with the free cells. In comparison with the free cells, the immobilized cells required 30% less light energy at a H2S removal rate of 2 mM/(L‐h) and showed an activity of 2.4 times that of the free cells. However, in 40 h after the reaction the deterioration of the H2S removal efficiency became significant due to the accumulation of sulfur in the beads. The scanning electron micrograph (SEM) and energy‐dispersive X‐ray spectrometer (EDS) studies showed that the sulfur in the beads existed within a layer of 0.4 mm from the bead surface. In the sulfur‐settling free‐cell recycle reactor, about 80% of the sulfur excreted by the free cells could be removed in a settler. The 4‐L fed batch reactor with the settler improved the light transmission to result in a H2S removal rate of 3 μmol/ (mg of protein‐h), 50% higher than that without it. The settling recycle reactor was much better in the removal of H2S than the immobilized‐cell reactor because the former was a continuous system with the constant removal of sulfur particles by settling and of spent medium by supplying fresh medium at the same rate as the filtering rate of the reactor broth, while the latter was essentially a batch system where toxic metabolites and produced sulfur could not be removed.
Effect of Serum on the Plasma Membrane Fluidity of Hybridomas: An Insight into Its Shear Protective Mechanism
Authors: Ramirez Octavio T. , Mutharasan R. 
Published: March 2005

AbstractWe have previously shown that decreasing the concentration of fetal bovine serum (FBS) increased the fragility of a mouse hybridoma (HB‐32) during agitated batch cultivation and that increasing the plasma membrane fluidity (PMF) increased the shear sensitivity during exposure to laminar flow. In this study, the effect of FBS concentration on the PMF of HB‐32 was investigated. PMF was evaluated by steadystate fluorescence anisotropy (r8) of 1‐[4‐(trimethylamino) phenyl]‐6‐phenylhexa‐1,3,5‐triene. Increasing serum concentration increased the r8 of hybridomas, indicating a decrease in their PMF. The effect of cholesterol modulation on the PMF and shear sensitivity was also evaluated. Hybridomas were exposed to turbulent fluid shear after modification of PMF by cholesterol modulation. Direct cholesterol enrichment of the plasma membranes caused a decrease in the PMF and shear sensitivity, while cholesterol depletion caused an increase in PMF and shear sensitivity. Low‐and high‐density lipoprotein supplementation to cultures in serum‐free or complete medium decreased their shear sensitivity. Lipoprotein supplementation to serum‐free cultures decreased the PMF. Altogether, these results suggest that the protective mechanism of serum against hydrodynamic damage relies, at least partially, on its ability to decrease the PMF of hybridomas possibly through the transfer of cholesterol from the serum lipoproteins into the plasma membrane.
Kinetic Properties of Myrosinase in Hydrated Reverse Micelles
Authors: Hochkoeppler Alejandro , Palmieri Sandro 
Published: March 2005

AbstractThe enzymatic activity of myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1) solubilized in reverse micelles, which were formed in isooctane by bis(2‐ethylhexyl) sodium sulfosuccinate (AOT), was studied using sinigrin (allyl glucosinolate) and glucotropeolin (benzyl glucosinolate) as substrates. The enzyme in reverse micelles follows Michaelis‐Menten kinetics for both substrates, showing similar kinetic values, whereas in water solution sinigrin seems to be the better substrate. The effect of the water concentration, W0 (W0=[H20]/[AOT]), on the steady‐state velocity of the myrosinase does not induce the bell‐shaped activity profile observed for many other enzymes. The optimal W0 for both substrates appears to be widespread between 10 and 40. The pH profile of myrosinase activity in reverse micelles shows an increase of activity from pH 4 to pH 6. Above this value and up to pH 9, the activity remains constant, establishing a broad plateau at its maximum. It was demonstrated that myrosinase activity in reverse micelles, as well as in water solution, strongly depends on the temperature, showing an extraordinary maximum of activity with both substrates around 60 °C. As in water, the enzyme appears to be strongly activated by ascorbate in reverse micelles with both sinigrin and glucotropeolin. All the above properties of the enzyme in reverse micelles, and in particular (i) the possibility of varying the water concentration and the pH within relatively wide ranges, (ii) the high thermal stability of the enzyme together with the exceptionally high optimum reaction temperature, and (iii) the activation of the enzyme by ascorbate more than in water solutions, strongly suggest the use of this enzyme solubilized in reverse micelles to good advantage for producing biologically interesting nitrogen‐and sulfur‐containing compounds from glucosinolate hydrolysis.
A Stable Long‐Term Hepatocyte Culture System for Studies of Physiologic Processes: Cytokine Stimulation of the Acute Phase Response in Rat and Human Hepatocytes
Authors: Bader Augustinus , Rinkes Inne H. Borel , Closs Ellen I. , Ryan Colleen M. , Toner Mehmet , Cunningham James M. , Tompkins Ronald G. , Yarmush Martin L. 
Published: March 2005

AbstractPrior studies on the in vitro hepatic acute phase response have involved either hepatoma cell lines or conventional short‐term cultures of primary hepatocytes. No data are available on the response of primary hepatocytes in stable long‐term culture systems. In this study, the acute phase response of rat and human hepatocytes in a new long‐term culture system was examined in response to interleukin‐6 (IL‐6), interleukin‐1β (IL‐1β), and tumor necrosis factor α (TNF‐α). The cultured cells were sandwiched between two layers of collagen in a (double‐gel) configuration which has been shown to preserve both hepatocyte function and morphology over prolonged periods of time. The stability of this culture configuration enabled us to investigate, for the first time, the temporal aspects of the response in addition to the effects of the mediators on protein secretion. Exposure of rat hepatocytes to IL‐6 after culture for 16 days resulted in a 2‐fold reduction of albumin secretion and a 15‐fold increase in the secretion rates of fibrinogen and α2‐macroglobulin. In all instances, the peak response occurred at 48 h after IL‐6 exposure, and all protein secretion rates returned to pretreatment values within 5 days post‐treatment. Changes in the mRNA levels of these proteins in response to IL‐6 corresponded with those changes seen with the secreted products, indicating pretranslational regulation. Administration of IL‐1β to rat hepatocytes produced a similar decline of albumin secretion and a 5‐fold increase of fibrinogen secretion, whereas α2‐macroglobulin secretion remained undisturbed. In contrast, TNF‐α did not affect the secretion of any protein examined. Human hepatocytes in a double‐gel culture configuration reacted to IL‐6 and IL‐1β with an approximate 40‐fold increase in serum amyloid A secretion, peaking at day 3 posttreatment. Both the secretion pattern and temporal response of these cultured hepatocytes to cytokines appear to closely mimic the in vivo hepatocellular response. The double‐gel culture system is a stable, attractive tool for further investigation of the acute phase and other hepatocellular responses to physiologic stimuli.
Oxygen Mass Transfer Enhancement via Fermentor Headspace Pressurization
Authors: Yang Jeng‐Dar , Wang Nam Sun 
Published: March 2005

AbstractBioreactor headspace pressurization represents an excellent means of enhancing oxygen mass transfer to a culture. This method is particularly effective in situations where stirring or vigorous aeration is difficult. Because it in itself introduces no undesirable hydrodynamic force, the proposed method is also attractive for cells susceptible to agitation and sparging. Experiments were first conducted in an ideal fermentor by sparging air into a sulfite solution free from extraneous microbial effects. An increased oxygen mass transfer rate resulting from pressurization led to a superior cell growth rate and a higher maximum cell density in both of the microbial systems studied: a bacterial (Escherichia coli) culture up to 2.72 bar and a fragile algal (Ochromonas malhamensis) culture with pressure programming. Applying pressurization increased the maximum dry cell weight from 1.47 g/L to 1.77 g/L in the E. coli culture and increased the maximum viable cell density from 4 X107 cells/mL to 108 cells/mL in the algal culture. An additional advantage is that formation of undesirable products under oxygen limitation, e.g., acetic acid in the E. coli culture, can be suppressed. A significant (over 250%) improvement in the oxygen transfer rate can be achieved with existing fermentors with little modification as they are already designed to withstand reasonable pressure from autoclaving. This method is simple, clean, inexpensive, and easily implemented, and it can be applied alongside other existing methods of oxygen mass transfer enhancement.
Production and Purification of a Recombinant Elastomeric Polypeptide, G‐(VPGVG)19‐VPGV, from Escherichia coli
Authors: Mcpherson David T. , Morrow Casey , Minehan Daniel S. , Wu Jianguo , Hunter Eric , Urry Dan W. 
Published: March 2005

AbstractAn elastomeric polypeptide was produced, with the sequence G‐(VPGVG)19‐VPGV, as a fusion to glutathione S‐transferase using the vector pGEX‐3X. The fusion protein was expressed to high levels in Escherichia coli as indicated by SDS‐PAGE analysis of induced cells. The fusion protein was affinity purified and cleaved with protease factor Xa, and the elastomeric polypeptide was recovered to a high degree of purity as indicated by SDS—PAGE followed by staining with CuCl2. The physical characterizations of carbon‐13 and proton nuclear magnetic resonance and of the temperature profile for turbidity formation for the inverse temperature transition of hydrophobic folding and assembly attest to the successful microbial synthesis of the polypentapeptide of elastin. The results of these studies provide the initial progress toward achieving a more economical and practical means of producing material for elastic protein‐based polymer research and applications.
Fully‐Automatic Measurement of Mycelial Morphology by Image Analysis
Authors: Tucker Keith G. , Kelly Tom , Delgrazia Patricia , Thomas Colin R. 
Published: March 2005

AbstractA fully‐automatic image analysis method is described for the comprehensive and quantitative analysis of the morphology of filamentous mycelia grown in submerged cultures. The method not only allows rapid measurement of important morphological parameters on freely dispersed mycelia but also provides a novel characterization of the aggregated (clumped) form. The latter can constitute more than 90% of the biomass in some fermentations and might therefore be expected to have a major influence on broth rheology, fermenter mixing, mass transfer, and hence fermentation productivity. Clumps are characterized not only in terms of the percentage of mycelia in this form, as in earlier work, but also in terms of clump area, perimeter, compactness, and roughness. The method has been tested on laboratory‐scale Streptomyces clavuligerus and Penicillium chrysogenum fermentations. It is not only more comprehensive than previous methods but also faster and thus will permit more extensive physiological and engineering studies on mycelial fermentations than has previously been possible.
Screening of Insect Cell Lines for the Production of Recombinant Proteins and Infectious Virus in the Baculovirus Expression System
Authors: Wickham T. J. , Davis T. , Granados R. R. , Shuler M. L. , Wood H. A. 
Published: March 2005

AbstractEight cell lines derived from the insects Spodoptera frugiperda, Trichoplusia ni, Mamestra brassicae, and Estigmene acrea were evaluated for recombinant β‐galac‐tosidase and infectious virus production following infection with the baculovirus Autographa californica multiple nuclear polyhedrosis virus (AcMNPV). Production was assessed on a specific (per cell and per microgram of uninfected cellular protein) and on a volumetric (per milliliter) basis. Cell density was found to be an important factor in comparing the cell lines due to a density‐dependent inhibition of specific protein and virus production that appeared to result from cell‐cell contact. After infection of cells at low‐density specific β‐galactosidase production per cell would drop between β‐ and 6‐fold in five of the eight cell lines when plated on tissue culture plates at near‐confluent and confluent cell densities. The cell lines Sf 21 and Sf 9 were least sensitive to cell density. After accounting for cell density effects and differences in cell size, two cell lines, BTI Tn 5B1‐4 and BTI TnM, were identified that were superior to the other cell lines, including Sf 21 and Sf 9, in β‐galactosidase production. Optimal volumetric and specific β‐galactosidase production from Tn 5B1‐4 and TnM cells was 2‐fold and 5‐fold higher, respectively, in both cell lines than the optimal production from Sf 9 or Sf 21 cells. The Tn 5B1‐4 cell line also had the highest viability of all the cell lines at 3 days postinfection and could be adapted to serum‐free media. Specific (per microgram of cellular protein) infectious virus production between cell lines varied by less than 2‐fold between cell lines after cell size differences were taken into account. No correlation was found between recombinant protein and NOV production although both were found to decrease similarly with increasing cell density.
Fluctuations in Continuous Mammalian Cell Bioreactors with Retention
Authors: Vits Hugo , Hu Wei‐Shou 
Published: March 2005

AbstractContinuous flow bioreactors with cell retention have been increasingly used for the cultivation of mammalian cells. The potential advantages of such bioreactors are high cell concentrations and volumetric productivities. In many reported cases, these systems have shown fluctuations in cell concentrations of various frequency and magnitude. To analyze the dynamics of the fluctuations, a model‐based approach is followed. Simulations showed that large fluctuations in biomass resulted in response to fluctuations in the retention ratio when the system is operated at high dilution rate and high cell retention. The dependence of cell concentration fluctuations on variations in dilution rate and retention ratio was established by a cross‐correlation statistical analysis on available experimental data. The slower dynamics and the fluctuation propensity of retention systems suggest that continuous culture without retention is more convenient for kinetic studies. In all likelihood, continuous culture with retention can be stabilized by controlling both the retention ratio and the dilution rate.
Inactivation of Saccharomyces cerevisiae by Supercritical and Subcritical Carbon Dioxide
Authors: Lin Ho‐Mu , Yang Zhiying , Chen Li‐Fu 
Published: March 2005

AbstractYeast cells were inactivated by carbon dioxide at subcritical and supercritical temperatures over the pressure range of 1000–3000 psi. A static apparatus was developed for the experiments. The results showed that a maximum of 15 min, depending on the pressure, was sufficient to inactivate yeast cells by 107‐fold under supercritical conditions. Subcritical carbon dioxide was found to be much less effective. It took 30–40 min to achieve inactivation of 104‐fold and more than 1 h to achieve inactivation of 107‐fold. There are two distinct mechanisms in the deactivation of yeast cells. The rate of cell inactivation is slow at first and increases drastically at the later stage, suggesting that the penetration of CO2 into microbial cells was a primary controlling factor of the inactivation process. The inactivation rate was enhanced remarkably by a series of pressure release/recompression of CO2 in the midst of a complete experiment. Other methods to improve the efficiency of inactivation are discussed.
Mass Transfer in an Airlift Reactor with a Net Draft Tube
Authors: Wu Wen‐Teng , Wu Jiumn‐Yih , Jong Jian‐Zhong 
Published: March 2005

AbstractGas–liquid mass transfer in an airlift reactor with net draft tube is investigated. The effects of both the ratio of draft tube to reactor diameter and the reactor pressure on oxygen transfer are considered. The value of the volumetric mass transfer coefficient, kLa, increases with a decreasing diameter ratio at higher air flow rates. The correlation of volumetric mass transfer coefficient with respect to the true superficial air velocity under different reactor pressures is determined. The kLa value decreases with increasing reactor pressure.
On‐Line Assessment of Metabolic Activities Based on Culture Redox Potential and Dissolved Oxygen Profiles During Aerobic Fermentation
Authors: Kwong Simon C. W. , Randers Lisa , Rao Govind 
Published: March 2005

AbstractWe report here on the utility of on‐line culture redox potential and dissolved oxygen measurements to identify metabolic changes in fermentation by Corynebacterium glutamicum under aerobic conditions. Metabolic changes were identified by observing discrepancies in the profile of culture redox potential and dissolved oxygen. On the basis of these measurements, we can identify the end of the lag phase, threonine exhaustion, and glucose exhaustion during fermentation.
Altered Distribution of Mitochondria and Actin Fibers in 3T3 Cells Cultured on Microcarriers
Authors: Laney Tracey V.Du , Cherry Robert S. , Coppinger Justine A. , Truskey George A. 
Published: March 2005

AbstractThe mitochondria and actin fibers of 3T3 fibroblasts cultured on microcarriers in spinner flasks were visualized using fluorescent stains. In contrast to cells grown on planar surfaces under static or steady laminar flow conditions, cells exposed to higher levels of turbulent agitation do not form actin stress fibers. Greater agitation also leads to a more diffuse appearance of the mitochondria and a wider distribution of them throughout the cytoplasm. This response may indicate damaged mitochondria, as similar results have been reported for chemical toxins.
A Correlation for the Effective Strength of Escherichia coli during Homogenization
Authors: Middelberg Anton P. J. , O'Neill Brian K. 
Published: March 2005

AbstractA new model for high‐pressure homogenization has been previously developed. A key model parameter, the mean effective cell strength, can be correlated with average cell length and peptidoglycan cross‐linkage. In this article, we develop a correlation for mean effective strength based on a statistical thermodynamic approach to fracture. The final correlation provides an unbiased estimate. While it offers no numerical advantage over a previous empirical correlation, it is based on a modeling approach and an understanding of wall structure. The variable groupings are therefore justifiable.
Complex Coacervate Microcapsules for Mammalian Cell Culture and Artificial Organ Development
Authors: Matthew Howard W. , Salley Steven O. , Peterson Ward D. , Klein Michael D. 
Published: March 2005

AbstractA number of combinations of anionic and cationic polymers, the majority being polysaccharides, were screened to determine their suitability for the development of alternative microcapsule formulations capable of supporting cells. The capsules were taken through a limited optimization and then evaluated on the bases of rupture strength, permeability to albumin, and ability of their components to promote the attachment, aggregation, and function of encapsulated rabbit hepatocytes. The widely used alginate—polylysine capsules were employed as a comparative standard in all tests. A number of the new formulations compared favorably with the standard, and some exhibited superior performance in specific areas. Hepatocyte function, as evaluated by the rate of urea synthesis, showed no significant differences between formulations over a 24‐h test period. One formulation, composed of the polysaccharides (carboxymethyl) cellulose, chondroitin sulfate A, chitosan, and polygalacturonate, was found to be superior to alginate—polylysine capsules in the areas investigated and supported the long‐term survival and growth of liver endothelial cells.
Production of Poly(hydroxybutyrate) Homopolymer and Copolymer from Ethanol and Propanol in a Fed‐Batch Culture
Authors: Alderete Jason E. , Karl Daniel W. , Park Chang‐Ho 
Published: March 2005

AbstractProduction of poly (hydroxy butyrate) (PHB) homopolymer and poly(hydroxybutyrate‐valerate) (PHBV) copolymer by a mutant strain of Alcaligenes eutrophus was studied in a 7‐L fed‐batch fermentor using ethanol and propan‐1‐o1 as sole carbon sources. Decreasing the initial phosphate concentration to 20% of the original Repaske medium allowed exhaustion of the phosphate during logarithmic growth and was an effective means of PHB(V) induction. Up to 74% PHB by weight was obtained with 63 g/L of dry cell mass. The copolymer content increased with a higher fraction of propan‐1‐o1 in the feed and reached a maximum of 35.2 mol % from pure propan‐1‐o1. Gradual oxygen limitation during the late log phase induced 21.9% PHB by weight.