bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Anionic Galactomannan Polysaccharide Gum from a Newly‐Isolated Lactose‐Utilizing Bacterium. II. Fermentation Kinetics and Lactose Transport
Authors: Flatt James H. , Cooper Timothy A. , Gonzalez Juan M. , Dogger Dina E. , Lightfoot Edwin N. , Cameron Douglas C. 
Published: March 2005

AbstractThe facultative bacterium Erwinia ATCC 55046, isolated from the soil of a wheytreated farm field, produces an anionic galactomannan polysaccharide gum (designated lactan gum) from lactose and other sugars. On lactose semidefined medium in a 5‐L fermentor, the organism had a maximum growth rate of 0.66 h−1 and produced 26 g/L polysaccharide with a yield on lactose of 0.66 g/g and a volumetric productivity of 0.6 g/(L.h). In shake flasks, the best final gum concentration was obtained with a carbon to nitrogen ratio of 40:1 (w/w). Gum yield and concentration was greater on disaccharides than on monosaccharides. The organism was found to transport lactose by a permease system as opposed to a phosphotransferase system. Lactan gum can be produced efficiently from lactose, the major sugar in whey and whey permeate.
A Fiber‐Optic System for Measuring Single Excitation‐Dual Emission Fluorescence Ratios in Real Time
Authors: Mccarthy John F. , Magin Richard L. , Kisaalita William S. , Slininger Patricia J. 
Published: March 2005

AbstractThe development and subsequent evaluation of a fiber‐optic system for measuring single excitation—dual emission fluorescence ratios in real time is described. The design of the flashlamp excitation source, optics, electronics, and computer software is discussed. The dual emission pH sensitive fluorophore 1, 4‐dihydroxyphthalonitrile (1, 4‐DHPN) was used to test the performance of this system. The flexible design of this modular system permits the use of other single excitation—dual emission fluorophores by simply changing the appropriate optical filters. Upon a single 340–380‐nm excitation, pH‐sensitive emissions were monitored at 488 nm and 434 nm. The ratio of these emissions (488/434) was then computed in real time, for a 2 mM solution of 1, 4‐DHPN, while the pH was titrated over the range 5–9. The nonlinear, system‐dependent, calibration curve of pH versus the ratio of emission wavelengths was empirical fit by a fourth‐order polynomial (r2 = 0.995). Reliable pH measurements in the range 6–8 were obtained using concentrations of 1, 4‐DHPN as low as 50 μM. The standard deviation of pH measurements using a 1 mM solution of 1, 4‐DHPN, near neutral pH, was found to be approximately 0.1 pH unit.
Electrokinetic Isolation of Vesicles and Ribosomes Derived from Serratia marcescens
Authors: Hawker Debra T. L. , Todd Paul , Davis Robert H. , Lawson Robert C. , Rudge Scott R. 
Published: March 2005

AbstractRibosomes and vesicles derived from the bacterium Serratia marcescens were separated from each other and from solubles using density gradient electrophoresis. Transport relationships were used to determine the electrophoretic mobilities of the particles. The effects of convection, sedimentation and diffusion were found to be negligible. The electrophoretic mobility obtained for the ribosome peak is –7 × 10–5 cm2/(V.s). Under appropriate conditions, two vesicle peaks were obtained, the first with a mobility of –4 × 10–5 cm2/(V.s) and the second with –9 × 10−6 cm2/(V.s). This information can be used to predict the resolution of the separands in large‐scale electrophoretic separations.
Techniques for Studies on Growth Characteristics of Human Prostatic Cancer Cells
Authors: Bauer Johann , Grimm Daniela , Hofstaedter Ferdinand , Wieland Wolf 
Published: March 2005

AbstractThe methods described in this article seem to be useful for studies on the growth characteristics of malignant epithelial prostate cells which are still under the influence of healthy cells. Before establishing primary cultures, pieces of tissue were sectioned in such a way that they could be unfolded to obtain a large surface. These pieces were treated enzymatically and then incubated for at least 4–6 weeks. In this time, cells grew or migrated out of the tissue and spread over the surface of the culture flasks. The viable single cells harvested from these primary cultures were characterized flow cytometrically, fractionated by countercurrent centrifugal elutriation, or further incubated above agarose so that they formed three‐dimensional spheroids. Cytometric determinations of cellular cytokeratin, vimentin, and DNA were performed before and after incubation. They suggested that the percentages of cytokeratin‐positive (epithelial) cells, vimentin‐positive cells (fibroblasts), and aneuploid cells remained at levels (in vitro) similar to those within the pieces of tissue used for the culturing experiments, respectively. Since our culture technique allows the propagation of human epithelial prostate cells in vitro as they would grow in vivo under the control of the surrounding tissue, the method should help to investigate which particular treatment of the cells influences the growth of the malignant cells, while they are still surrounded by other cells of the same prostatic organ.
Cation‐Exchange Displacement Chromatography of Proteins with Protamine Displacers: Effect of Induced Salt Gradients
Authors: Gerstner Joseph A. , Cramer Steven M. 
Published: March 2005

AbstractProtamine was investigated for its utility as a protein displacer in cation‐exchange systems. Although the protamine solution contained several variants of the molecule, the high affinity of all of the components in this heterogeneous biopolymer enabled it to act as an efficient protein displacer. To facilitate parameter estimation of the protamine, a preliminary purification was carried out by preparative elution chromatography. Chromatographic parameters of both the feed proteins and protamine displacer were obtained for use in a multicomponent steric mass action ion‐exchange displacement model. Model simulations were compared to displacement results under both moderate and intense induced salt gradient conditions. In both cases, excellent agreement was obtained between the displacement experiments and theoretical predictions. In addition, these studies serve to dramatize the importance of induced salt gradients in ion‐exchange displacement systems.
One‐Step Purification of a Model Periplasmic Protein from Inclusion Bodies by Its Fusion to an Effective Metal‐Binding Peptide
Authors: Beitle Robert R. , Ataai Mohammad M. 
Published: March 2005

AbstractIt has been demonstrated that the addition of a metal‐binding amino acid sequence to an exposed terminus of a protein can be useful for purification using immobilized metal affinity chromatography (IMAC). Polyhistidine extensions, wherein sequential histidyl residues are placed at the end of a protein, have been utilized for protein purification through IMAC. Natural metal‐binding peptides may also serve as starting points for the design of an affinity tail. As a model system, an octapeptide derived from angiotensin I was fused to TEM‐β‐lactamase. When the modified protein was expressed in Escherichia coli, a one‐step purification of this recombinant protein was accomplished from resolubilized inclusion body material.
Compressive Characteristics of Freeze‐Dried Agar and Alginate Gel Sponges
Authors: Nussinovitch A. , Velez‐Silvestre R. , Peleg M. 
Published: March 2005

AbstractMechanically stable solid sponges can be produced by freeze drying 2 % agar and 1 % alginate gels. The sponges have characteristic compressive stress‐strain curves that can be described by a three‐parameter model originally developed for polymeric sponges and bakery products. Internally produced bubbles, formed by immersing bicarbonate‐containing gels in an acid bath, resulted in a considerable loss of mechanial integrity in the dry agar sponges but not in those of the alginate.
Increased Activity of Chromobacterium viscosum Lipase in Aerosol OT Reverse Micelles in the Presence of Nonionic Surfactants
Authors: Yamada Yasushi , Kuboi Ryoichi , Komasawa Isao 
Published: March 2005

AbstractModification of AOT reverse micellar systems with various alkyl glucosides and nonionic surfactants was attempted in order to improve the activity to Chromobacterium viscosum lipase. Tweens and Tritons, having the poly(oxyethylene) chain, have been shown to be solubilized at the oil—water interface of AOT micelles. Alkyl glucosides were also solubilized at the interface. These additives form mixed micelles with AOT and increase the concentration of the micelles. In contrast, Spans were found to be solubilized in the micro water pool of AOT micelles. Addition of nonionic surfactants decreased the hydrophobicity of the reverse micellar systems. Improvement of the lipase activity was achieved by the addition of nonionic surfactants, because of suppression of the hydrophobic and electrostatic interaction between AOT and lipase. The addition of nonionic surfactant having a poly(oxyethylene) chain has been shown to effectively increase the activity of the lipase in reverse micelles.
Effect of Silicone Antifoam on Shear Sensitivity of Hybridoma Cells in Sparged Cultures
Authors: Van Der Pol Leo A. , Bonarius Dick , Van De Wouw Geert , Tramper Johannes 
Published: March 2005

AbstractAddition of high concentrations of silicone antifoam (AF) to a suspension of hybridoma cells in a bubble column reduces the death rate when using medium without a protective component. In contrast, high AF concentrations can cause detrimental effects in a sparged medium with a protective component, such as is applied for large‐scale animal cell cultures.
Evaluation of Crude Hydroxypropyl Starch As a Bioseparation Aqueous‐Phase‐Forming Polymer
Authors: Venǎncio Armando , Teixeira José A. , Mota Manuel 
Published: March 2005

AbstractA new aqueous two‐phase system based on crude hydroxypropyl starch (HPS) and poly(ethylene glycol) (PEG) is described. Unlike other polymer‐polymer aqueous two‐phase systems, the HPS used is commercially available. Previous works have characterized almost exclusively purified carbohydrates or their derivatives, having neglected the large amount of gums and carbohydrates already used in the paper, food, or textile industries. Two‐phase aqueous polymer systems based on such commercial polymers may have as a drawback their degree of purity, which may affect the separation procedure. However, their lower cost should encourage studies on their use in aqueous two‐phase polymer extraction. The influence of temperature, pH, and ionic strength on the partition of several different molecular weight and isoelectric point proteins and whole cells was studied. The results obtained were compared with corresponding dextran‐PEG systems, Aquaphase PPT‐PEG systems, crude dextran‐PEG systems, maltodextrin‐PEG systems, and Klucel L‐pluronic systems. Protein partition coefficient results exhibited higher values than those in corresponding systems. It is shown that this system, based on a crude hydroxypropyl starch, is highly attractive as an initial purification step.
Dissolved Carbon Dioxide Measurement and Its Correlation with Operating Parameters in Fermentation Processes
Authors: Dahod Samun K. 
Published: March 2005

AbstractA silicone tubing probe was used to measure dissolved carbon dioxide in two industrial fermentation processes. The two processes differed markedly in their broth viscosities: one had high viscosity (2000–3000 cP) and the other had low viscosity (<100 cP). The goal was to study changes in dissolved carbon dioxide concentration in fermentation broth when operating parameters, such as total pressure, air flow rate and, agitation rate, were modified. It was shown that in high‐viscosity fermentation broths the dissolved carbon dioxide concentration can reach as high as 190% of that calculated by assuming an equilibrium between the air coming out of the fermentor and the fermentation broth. For low‐viscosity broth, the highest dissolved carbon dioxide concentration was found to be about 133 % of the equilibrium value. On the basis of the material balance over the entire fermentor, the ratio of actual dissolved carbon dioxide partial pressure and carbon dioxide partial pressure in air leaving the fermentor was correlated to the operating parameters of pressure, air flow, and carbon dioxide transfer coefficient. Since carbon dioxide transfer coefficients are not readily available, we recommend a method of using oxygen transfer coefficients to develop a correlation that can be used on‐line to predict changes in dissolved carbon dioxide concentration when operating parameters are changed or when process improvements and scale‐up are undertaken.
Production of Human Alkaline Phosphatase, a Secreted, Glycosylated Protein, from a Baculovirus Expression System and the Attachment‐Dependent Cell Line Trichoplusia ni BTI‐Tn 5B1‐4 Using a Split‐Flow, Air‐Lift Bioreactor
Authors: Chung I. S. , Taticek R. A. , Shuler M. L. 
Published: March 2005

AbstractA split‐flow, air‐lift bioreactor for the cultivation of insect cells to produce recombinant protein is described. It can be used advantageously with attached cell systems. This bioreactor incorporates two sections: a rise and a downcomer. Trichoplusia ni BTI‐Tn 5B1‐4 cells are grown on a support material of glass beads or microcarriers placed in the downcomer. This cell line is more productive than other commonly used insect cell lines, but it has the disadvantage of being difficult to use at large volumes since it is not easily adaptable to suspension culture. Adequate oxygen demand is supplied by sparging without direct exposure of cells to air bubbles. Nutrients are supplied convectively to the attached cells on support material as the fluid flows through the downcomer. The split‐flow, air‐lift bioreactor appears to be suitable for insect cell culture and is potentially scalable. It can provide a high surface‐to‐volume ratio and can be operated in batch or continuous mode. A lab‐scale prototype bioreactor has been constructed and tested for the production of a secreted, glycosylated recombinant protein (human alkaline phosphatase) or seAP using an Autographa californica multiple nuclear polyhedrosis virus (AcMNPV) vector. With a ratio of riser cross‐sectional area to downcomer cross‐sectional area of 1, an aspect ratio of 4.4, an air‐flow rate of 54 mL/min in the riser, and a bed of 2400 3‐min nonporous glass beads, 10.7 μg/mL of seAP was produced using an MOI (multiplicity of infection or the ratio of plaque‐forming units to cells) of 10. On a specific productivity basis, the split‐flow, air‐lift system and T‐flasks gave similar values (about 13 μg/106 cells).
Ethanol Production in Baker's Yeast: Application of Experimental Perturbation Techniques for Model Development and Resultant Changes in Flux Control Analysis
Authors: Schlosser Paul M. , Riedy Gerard , Bailey James E. 
Published: March 2005

AbstractRecent theoretical results (Schlosser and Bailey, 1990; Schlosser et al., 1993) suggest that it is possible to model elements of metabolism to the extent necessary for flux control analysis using only the results of perturbation experiments. In particular, the development of detailed, mechanistic descriptions of certain relevant processes (which would otherwise require prohibitive effort) can be avoided by direct use of experimental results. Anaerobic glycolysis in Saccharomyces cerevisiae AMW‐13C was studied both under unperturbed conditions and under several experimental perturbations. Changes in pathway fluxes and metabolite levels relative to the unperturbed values were observed and analyzed to determine the relationships that exist between several of these quantities. These relationships were used to refine and extend a previously determined model for the glycolytic pathway (Galazzo and Bailey, 1990, 1991). The refined model was then used to study the flux control characteristics of the pathway. The analysis indicates that the reaction catalyzed by phosphofructokinase (PFK), while retaining significant flux control, is less important than previous studies suggested and that glucose uptake is the predominant rate‐controlling step when small changes are considered. The model indicates that larger increases in the amount of any single pathway enzyme yield no more than a 36% increase in ethanol production.
Intermolecular Electrostatic Interactions and Their Effect on Flux and Protein Deposition during Protein Filtration
Authors: Palecek Sean P. , Zydney Andrew L. 
Published: March 2005

AbstractAlthough membrane filtration is used extensively to process protein solutions containing a variety of electrolytes, there is currently little fundamental understanding of the effect of the solution environment (and in particular, the solution pH) on the filtrate flux in these systems. We have obtained data for the flux and sieving coefficients during the batch (stirred cell) filtration of solutions of bovine serum albumin, immunoglobulins, hemoglobin, ribpnuclease A, and lysozyme through 0.16‐μm micro‐filtration membranes at different pH values. The flux declined significantly for all five proteins due to the formation of a protein deposit on the upper surface of the membrane. The quasi‐steady ultrafiltrate fluxes at the individual protein isoelectric pH's were essentially identical, despite the large differences in molecular weight and physico‐chemical characteristics of these proteins. The flux increased at pH's away from the isoelectric point, with the data well‐correlated with the protein surface charge density. These results were explained in terms of a simple physical model in which the protein deposit continues to grow, and thus the flux continues to decline, until the drag force on the proteins associated with the filtrate flow is no longer able to overcome the intermolecular repulsive interactions between the proteins in the bulk solution and those in the protein deposit on the surface of the membrane.
Use of Binding Measurements To Predict Elicitor Dosage Requirements for Secondary Metabolite Production from Root Cultures
Authors: Singh Gurmeet , Reddy G. Ramakrishna , Curtis Wayne R. 
Published: March 2005

AbstractThe strength of binding of a fungal elicitor derived from Rhizoctonia solani to Agrobacterium‐transformed root cultures of Hyoscyamus muticus is assessed. Two techniques are used to estimate the equilibrium binding constant: (1) a dose response, which involves the measurement of sesquiterpene formation in the presence of different amounts of elicitor, and (2) elicitor‐contacting experiments in which the root tissue is exposed to the elicitor for a short period of time and then the unbound elicitor concentration is determined by a bioassay. The equilibrium binding constants estimated by these two techniques were on the same order of magnitude. The value predicted from the dose response technique was 6.44 (mmol of glucose equiv/L of medium)−1, while that obtained from elicitor contact was 1.89 (mmol of glucose equiv/L of medium)−1. The higher binding constant measured by dose response may result from feedback inhibition of secondary metabolite formation at higher elicitor dosages. The magnitude of the binding'constant indicates that elicitor dosage is dependent upon both the amount of tissue in the reactor and the amount of medium present to dilute the added elicitor. Since proposed reactor configurations for plant root culture vary from 200 to 2000 g of tissue per liter of medium, elicitor dosage requirements will vary significantly depending upon the reactor operational conditions. This influence of elicitor binding on reactor design and operation is discussed.
Acid Hydrolysis of K‐Carrageenan in a Batch Reactor: Stochastic Simulation of Change of Molecular Weight Distribution with Time
Authors: Singh S. K. , Shen B. C. , Chou S. T. , Fan L. T. 
Published: March 2005

AbstractThe degradation of K‐carrageenan by acid hydrolysis in a LiCl/HCl (pH 2) buffer solution has been studied at various temperatures in a batch reactor. The reduction in the weight‐average molecular weight and the variation in the molecular weight distribution (MWD) have been followed over time by an SEC‐MALLS‐RI chromatography system. While a deterministic rate equation can be fit to the average molecular weight‐time data, this is not the case for the MWD‐time data. Since depolymerization by hydrolysis usually proceeds via nonspecific (random) bond cleavage, a stochastic approach can be appropriate for the resultant MWD‐time data. In the present work, the master equation has been derived from the stochastic population balance for this batch hydrolysis system characterized by a set of discrete states, each representing a particular molecular weight range. The governing equations for the means, variances, and covariances of the random variables, each representing the number of carrageenan molecules in an individual state, have been extracted from the master equation. The equations for the means have been applied to the MWD‐reaction time data, and the unknown reaction rate parameters have been estimated. These parameters can be used to generate the MWD at any hydrolysis reaction time from any initial MWD. The applicability, limitations, advantages, and sources of error of the derived model have been discussed.
Study of Nitrate Metabolism of Escherichia coli Using Fluorescence
Authors: Trivedi Hiren K. , Ju Lu‐Kwang 
Published: March 2005

AbstractPublic concern about environmental nitrate contamination has increased significantly. To investigate the nitrate metabolism of Escherichia coli, profiles of NAD(P)H fluorescence responding to nitrate/nitrite additions to anaerobic E. coli cultures at the resting or minimum‐growth state were monitored by an on‐line fluorometer. Two different types of fluorescence profiles were observed. Upon nitrate addition, the fluorescence signal dropped instantaneously, indicating the presence of NAD(P)H‐dependent nitrate/nitrite reductases, without previous nitrate/nitrite induction. The signal remained at that level until all of the nitrate was reduced. In some cases, the signal then directly rose back to the earlier anaerobic level. In others, it partially recovered to an intermediate level, remained at that level for a period much longer than the first stage, and then returned to the anaerobic level. The single‐stage response implied that the nitrite formed by nitrate reduction was totally converted to ammonium simultaneously. The two‐stage response, however, resulted from intermediate nitrite accumulation: the rise in fluorescence at the end of the first stage signified nitrate depletion, and the second stage corresponded to reduction of the nitrite accumulated in the first stage. This is supported by the specific rates of nitrate and nitrite reduction determined from the fluorescence profiles. While the former (0.0138 ± 0.0026 g of NO3−‐N/(g of cells)‐h) was about the same in all the runs conducted, the latter was found to be 1 order of magnitude lower than the former in cultures showing the two‐stage response. The presence of ammonium, at 0–50 ppm NH4+‐N, was found to have no appreciable effect on the nitrate reduction rate for the E. coli studied.