bluuebunny/crossref_metadata_2025_split huggingface dataset:
Process Design, Economic Feasibility, and Market Potential for Nylon 1313 Produced from Erucic Acid
Authors: Van Dyne Donald L. , Blase Melvin G. 
Published: March 2005

AbstractNylon 1313, made from the erucic acid of crambe or industrial rapeseed oil, has excellent attributes for use in industry. Its durability, chemical and water resistance, dimensional stability, and electrical properties are valuable characteristics for numerous applications. The processes and economics in transforming erucic acid into brassylic acid and into nylon 1313 are detailed. A sensitivity analysis, developed on a LOTUS template, shows changes in the unit cost of producing nylon 1313 with changes in feedstock material costs and coproduct credits, the two most important factors in the economic feasibility of nylon 1313. The current market and future potential markets for nylon 1313 are discussed. Biotechnology can play an important role in the commercialization of nylon 1313 from erucic acid. Rapeseed is a crop of choice for many biotechnologists. Expected technological advances could lower the cost of crop production, thereby reducing the cost of nylon 1313. Success would improve the competitive position of nylon 1313 relative to other industrial nylons.
Design of Continuous Sterilization Systems for Fermentation Media Containing Suspended Solids
Authors: Armenante Piero M. , Leskowicz Mark A. 
Published: March 2005

AbstractA mathematical model was developed to analyze the performance of a continuous sterilizer fed with a liquid fermentation medium containing suspended solids. This type of medium is commonly used in the industrial practice of a number of fermentation processes. The unsteady‐state energy balance equations for the liquid and the suspended solids passing through each component of the system were solved analytically. A computer model was then used to calculate the temperature profiles in the liquid and in the solid particles as they move through the sterilizer, as well as the level of sterility achieved under different operating conditions. It appears that the level of sterility is always lower when solids are present in the system, as one may anticipate. The temperature gradients produced in the solids as a result of the unsteady‐state heat transfer occurring as the media moves through the heat exchangers in the system result in lower temperatures in the solid cores. This reduces the effectiveness of the process by protecting the microorganisms against thermal death. In some cases it was found that the level of sterility was so low that operating under such conditions would fail to produce a sterile product. The model was also used to assess the sensitivity of the sterilization process to changes in the most significant design and operating parameters for the case in which solids are present in the medium. The sterilization temperature, steam temperature, heat transfer coefficients in the heat exchangers, particle size, and residence time in the sterilizer holding section appear to be the most important of these parameters. The model obtained in this work can be used to design continuous sterilizers processing slurry media or to evaluate the performance of existing sterilizers.
Effect of Transcription Promoters on the Optimal Production of Secreted Protein in Fed‐Batch Reactors
Authors: Park Seujeung , Ramirez W. Fred 
Published: March 2005

AbstractProduction of heterologous proteins by yeast secretion imposes additional factors that need to be considered, which do not appear with production by direct expression. These include additional intracellular polypeptide processing dynamics through the secretory organelles and the protein concentration in the culture medium, which is the usual final destination of the product. Optimal control theory is applied to optimize fed‐batch production of secreted protein. We maximize an objective function that includes both total production rate and product concentration. A mutant invertase is chosen as the model heterologous secretory protein. Optimal control control strategies have been obtained for the use of two different promoters for the gene transcription, a derepressible SUC2 promoter and a strong glycolytic GPD promoter. With the use of the strong GPD promoter, achieving maximum production occurs on the singular arc of maximum specific growth rate. As the object switches to maximum product concentration, operation occurs for longer periods of time at a slow glucose singular arc condition. The optimal control for maximizing protein production with the weak SUC2 promoter requires transitions between high and low glucose concentrations associated with multiple distinct singular arc conditions. For maximum product concentration, the high concentration branches of the singular arc supporting maximum growth rate and maximum secretion rate disappear. Operation stays essentially on the low glucose concentration branch of the singular arc, which maximizes the protein production rate and minimizes the dilution of the broth product concentration.
Comparative Studies of Glucose Catabolism by Escherichia coli Grown in a Complex Medium under Aerobic and Anaerobic Conditions
Authors: Diaz‐Ricci Juan C. , Hitzmann Bernd , Rinas Ursula , Bailey James E. 
Published: March 2005

AbstractEscherichia coli HB101 was grown in complex medium under anaerobic and aerobic conditions. Cells prepared under these two different conditions were characterized by two‐dimensional protein gel electrophoresis, by NMR measurements under identical (anaerobic) conditions, and by measuring the kinetics of glucose uptake and catabolite end‐product appearance in the medium under identical anaerobic conditions. Specific rates of glucose uptake and end‐product formation were significantly greater for the anaerobically grown cells, which also exhibited lower intracellular concentrations of sugar phosphates, nucleoside di‐and triphosphates, UDPG, and NAD(H). Two‐dimensional gel electrophoretic analyses reveal changes in the intracellular levels of proteins involved in pyruvate catabolism that have been observed previously for E. coli grown in minimal medium under aerobic and anaerobic conditions. Enzymes involved in the TCA cycle were not detected in cells grown aerobically or anaerobically in complex medium.
Polymer Fractionation in Aqueous Two‐Phase Polymer Systems
Authors: Hartounian H. , Sandler S. I. 
Published: March 2005

AbstractWe consider the effects of the addition of poly(ethylene glycol) (PEG) of different molecular weights to aqueous two‐phase systems of PEG 8000 and dextran 500. The first purpose of this study was to determine the molecular weight partitioning of the polymers themselves so that, for example, aqueous two‐phase separations using affinity ligands can be improved. The second purpose was to examine whether this molecular weight partitioning could be predicted by using solution thermodynamic models so that it would be possible to optimize affinity partitioning without extensive laboratory work. Experimentally, we find that, by increasing the PEG concentration of any molecular weight in the feed, the high molecular weight PEG concentration in the dextran‐rich phase is reduced. This observation can be used to reduce the loss of expensive ligated PEG used in affinity partitioning. Further, there is generally good agreement between our experimental data and the predictions of a solution thermodynamic model.
Immobilization of Arthrobacter simplex in Thermally Reversible Hydrogels: Effect of Gel Hydrophobicity on Steroid Conversion
Authors: Park Tae Gwan , Hoffman Allan S 
Published: March 2005

AbstractArthrobacter simplex cells have been immobilized in a series of thermally reversible hydrogels having different gel hydrophobicities. Steroid conversion from hydrocortisone to prednisolone via the Δ1−dehydrogenase system was greatly affected by the relative hydrophobicities of the gel matrices, which were prepared by copolymerizing varying ratios of N‐isopropylacrylamide to acrylamide. The characteristics of the immobilized cells, such as optimal temperatures, Km values, and the effects of an added artificial electron acceptor, were largely influenced by the gel matrices and their different lower c	ritical solution temperatures (LCST). The data indicate that the microenvironment of the dehydrogenation system is quite different within the different hydrophilic/hydrophobic gel matrices. The high partitioning of water‐insoluble steroids into the hydrophobic regions and the reduced possibility of product inhibition within the more hydrophobic gel matrices may cause the observed higher steroid conversion in these gels. A possible model for immobilized A. simplex cells in such different gel matrices is proposed.
Production of Recombinant Proteins by Baculovirus‐Infected Gypsy Moth Cells
Authors: Betenbaugh Michael J , Balog Laura , Lee Po‐Shun 
Published: March 2005

AbstractAn experimental study was undertaken to evaluate alternative insect cell lines to Sf9 [from Spodoptera frugiperda (fall army worm)] for the production of recombinant proteins. Insect cell lines from two different organisms were considered: IPLB‐LdEIta (LdEIta) from Lymantria dispar (gypsy moth) and IPLB‐HvT1 (HvT1) from Heliothis virescens (tobacco budworm). Both LdEIta and HvT1 produced higher total activity levels of recombinant σ‐galactosidase in monolayer culture than Sf9 after infection with the Autographa californica nuclear polyhedrosis virus (AcMNPV). However, only LdEIta generated a product yield (activity per milligram of total protein) which exceeded that of Sf9 (by 25%), so its growth and production characteristics were investigated in depth. LdEIta generated production levels and yields of a recombinant rotaviral protein, VP4, which exceeded those of Sf9 by 84 and 38%, respectively. In suspension culture, the LdEIta cells grew as aggregates with a doubling time several hours longer than Sf9, but the recombinant product yields of LdEIta were still higher than Sf9 by 38% in this culture environment. σ‐Galactosidase expression rates and cell death rates suggested that the difference in productivity between the two hosts was due to the ability of LdEIta to survive the baculovirus infection and produce recombinant proteins longer than Sf9. The presence of LdEIta aggregates in suspension culture may be used as a method to separate live cells from dead cells, labile product, and spent medium in recombinant protein production processes.
Characterization of κ‐Carrageenan Gels Used for Immobilization of Bacillus firmus
Authors: Moon Seung‐Hyeon , Parulekar Satish J 
Published: March 2005

AbstractIn this study, aimed at a biochemical and physical characterization of κ‐carrageenan gels used for entrapment of Bacillus firmus NRS 783 (a superior producer of an alkaline protease), effects of carrageenan concentration, gelation temperature, initial cell loading, and strength of the curing agent (KC1) on the properties of cell‐free and cell‐laden gels were examined. The physical properties of the differently prepared gels that were examined included density, free volume fraction, mechanical strength, and change in gel volume during gel curing. The biochemical characteristics studied included viability of gel‐entrapped cells, cell leakage from cell‐laden gels, and cell penetration into cell‐free gels. For the range of carrageenan contents investigated [between 2 % and 5 % (w/v)], the mechanical strength of the gels with/without KC1 curing was observed to increase with an increase in carrageenan content of gels. The mechanical strength of each gel increased substantially upon extensive curing. Free volume fractions in excess of 0.8 were observed for all gels. Of cells that were viable prior to immobilization, 90–92 % remained viable after formation and extensive curing of gels for cell‐gel mixtures prepared at 45°C. Attempts at prolonged storage of cell‐laden gel beads at 0°C as stock cultures of immobilized B. firmus were unsuccessful due to a significant decline in cell viability during such storage. On the basis of the cell leakage studies, the average pore sizes of 2%, 3%, 4%, and 5% gels were deduced to increase in the following order of carrageenan content (w/v): 4%, 3%, 2%, and 5%. Commensurate with the decrease in the average pore size (or the increased tightness of the gels) with increasing carrageenan content, both the extent of cell leakage and the extent of net cell penetration decreased with increasing carrageenan content for the first three gels. Owing to nonuniform distribution of free space and much larger pores, the extent of net cell penetration in 5% carrageenan gels was considerably low, while the extent of cell leakage in 5% carrageenan gels was an order of magnitude greater than the extents of cell leakage in the other three gels.
Hemacytometer Cell Count Distributions: Implications of Non‐Poisson Behavior
Authors: Nielsen Lars K , Smyth Gordon K , Greenfield Paul F 
Published: March 2005

AbstractThe variance of observed cell counts using a hemacytometer was analyzed. The variance was found to be greater than expected under the normally assumed Poisson distribution because of variations in the volume of the counting area. Furthermore, counts from the two sides of the hemacytometer were found to be correlated. Total cell count on a hemacytometer was better described using a normal distribution with quadratic variance, N(λ,λ + σλ2), with σ=0.012. Because hemacytometer cell counts are not Poisson distributed, modified counting protocols are recommended.
Topical Paper: Modeling Transport Processes in Sterilization‐in‐Place
Authors: Noble Paul T. 
Published: March 2005

AbstractSIP (sterilization‐in‐place) of equipment using saturated steam is limited by transport processes that restrict the distribution of sterilizing steam. The following are two crucial operations: the removal of air prior to sterilization, and the removal of condensate during the sterilization. Using simple model systems of pipes and tanks, characteristic operating parameters were examined and steady‐state models were analyzed. The results were used to evaluate design aspects of SIP, including heat insulation, spacing of steam traps, sloping of lines, steam velocities and consumption, placement of temperature sensors, and scale factors in piping. A more reliable SIP design is achievable by insulating equipment, spacing steam traps to limit condensate buildup, providing an effective air removal operation, and providing reliable, high‐quality steam.
Effect of Oxygen Supply on the Suspension Culture of Genetically Modified Tobacco Cells
Authors: Gao Jianwei , Lee James M. 
Published: March 2005

AbstractThe effect of oxygen supply on the cultivation of the genetically modified tobacco cells and the formation of a foreign protein, β‐glucuronidase (GUS), was investigated in 250‐mL Erlenmeyer flasks, a 5‐L stirred tank fermenter, and a 7‐L air‐lift fermenter. The oxygen supply was varied by using different volumes of medium in the case of the 250‐mL Erlenmeyer flask culture or by the different aeration rate in the case of the two types of fermenters tested. Higher oxygen supply stimulated cell growth and increased oxygen consumption rate, the level of phenolics, and GUS productions.
Escherichia coli Host Cell Modifications in Continuous Culture Affecting Heterologous Protein Overproduction: A Population Dynamics Study
Authors: Fu Jeffrey , Togna A. Paul , Shuler Michael L. , Wilson David B. 
Published: March 2005

AbstractThere are many published studies of plasmid segregational instability in Escherichia coli in the literature. However, the formation of plasmid‐free segregants can be controlled by the addition of selective chemical agents like antibiotics. This solution has become commonplace in both the laboratory and industry. On the other hand, host cell modifications, which result in low production of plasmid‐encoded protein and lead to loss of culture productivity, have not been adequately addressed. Continuous culture of an inducible (ptac) Escherichia coli vector containing strain, RB791(pKN), was characterized by strong dynamic changes in the cell population and product (β‐lactamase) expression. Long‐term cultivation resulted in the loss of high‐level production ofβ‐lactamase. Loss of productivity was not due to the formation of plasmid‐free cells or structural modifications to the plasmid; instead, continuous operation resulted in a culture dominated by irreversibly altered, low‐producing cells. Two distinct classes of lac− mutants which inhibited induction were identified (Y− and Is).
Consistency Evaluation of Batch Fermentations Based on On‐Line NADH Fluorescence
Authors: Kwong Simon C. W. , Randers Lisa , Rao Govind 
Published: March 2005

AbstractThe profiles of on‐line NADH fluorescence as well as the profiles of NADH fluorescence versus dry cell weight (DCW) were used to compare the results of multiple batch fermentations. On the basis of off‐line kinetic parameter analyses, the results indicate that on‐line NADH fluorescence can be used to evaluate the consistency of the results of duplicate batch fermentations.
In Situ Studies of Protein Conformation in Supercritical Fluids: Trypsin in Carbon Dioxide
Authors: Zagrobelny Joann , Bright Frank V. 
Published: March 2005

AbstractThe conformation of the monomeric enzyme trypsin has been studied in supercritical carbon dioxide. Steady‐state fluorescence spectroscopy is used to follow the conformation of trypsin in situ as a function of CO2 density. Our results show for the first time that protein denaturation can occur during the fluid compression step and that the native trypsin is only slightly more stable (1.2 kcal/mol) than the unfolded form. These results demonstrate the power of fluorescence spectroscopy as a tool for studying protein conformation and dynamics in supercritical fluids.
Perfluorooctyl Bromide Dispersions in Aqueous Media for Biomedical Applications
Authors: Habif Stephane S. , Normand Pascal E. , Oleksiak Christian B. , Rosano Henri L. 
Published: March 2005

AbstractIn studying perfluorooctyl bromide (PFOB) dispersions in aqueous media, we have used two types of surfactant: egg yolk phospholipids (EYP) and polyglycerol esters (PGE). Our interest in these dispersions arises from their potential biomedical applications as imaging solutions and oxygen‐carrying solutions (i.e., blood substitutes). For EYP systems, we have identified the dispersion structure as consisting of (a) PFOB droplets (250‐nm diameter) stabilized by a phospholipid monolayer adsorbed irreversibly at the o/w interface and (b) small empty phospholipid vesicles. With both surfactants commercial preparations yielded stable systems, while purified samples, being non‐dispersible, could not be made to act as emulsifiers. In both cases, minor components in the commercial surfactant were found to be necessary for the formation of a stable dispersion, enabling the transport of the pure surfactant to the PFOB/water interface.
Optimizing the Sample Size and the Reduced Velocity To Achieve Maximum Production Rates of Enantiomers
Authors: Jacobson Stephen C. , Felinger Attila , Guiochon Georges 
Published: March 2005

AbstractOptimum experimental conditions are predicted for the maximum production rate of D‐ or L‐alanine, purified to a 99% purity from a racemic mixture of their N‐benzoyl derivatives by preparative chromatography on ionically immobilized bovine serum albumin. The experimental production rates and recovery yields measured under these conditions are in excellent agreement with the calculated values. These results validate the approach used for optimization of preparative liquid chromatography.
Effect of Protein Adsorption on the Transport Characteristics of Asymmetric Ultrafiltration Membranes
Authors: Mochizuki Seiichi , Zydney Andrew L. 
Published: March 2005

AbstractThe effects of bovine serum albumin adsorption on the transport characteristics of asymmetric poly(ether sulfone) ultrafiltration membranes were determined using polydisperse dextrans with gel permeation chromatograhy. Actual dextran sieving coefficients were evaluated from observed sieving data for both the clean and preadsorbed membranes using a stagnant film model. The flux dependence of the actual dextran sieving coefficients was used to evaluate the intrinsic membrane hindrance factors for convective (i.e., sieving) and diffusive transport for the different molecular weight dextrans using classical membrane transport theory. Protein adsorption caused a reduction in both dextran sieving and diffusion, with the magnitude of the reduction a function of the dextran molecular weight and pore size. The effects of adsorption on the specific pore area and the membrane porosity were then determined using a recent model for solute transport through asymmetric ultrafiltration membranes. The data indicate that protein adsorption occurs preferentially in the larger membrane pores, causing a greater reduction in solute sieving compared to the membrane hydraulic permeability and porosity than would be predicted on the basis of either a simple pore blockage or pore constriction model.
Effects of Plasmid Copy Number and Runaway Plasmid Replication on Overproduction and Excretion of β‐Lactamase from Escherichia coli
Authors: Paul Togna A. , Shuler Michael L. , Wilson David B. 
Published: March 2005

AbstractRunaway plasmid replication can be used to increase target gene dosage and thereby overproduce proteins within the bacterium Escherichia coli. However, the presence of excessive plasmid DNA often alters normal cell functions. High copy number plasmids with strong promoters place a severe metabolic burden on the cell, causing a decreased specific growth rate and changes in cell physiology. Induction of β‐lactamase synthesis from the tac promoter on plasmid pKN causes runaway plasmid replication and excretion of β‐lactamase. Runaway plasmid relication results from readthrough of tac promoter transcripts into the replication region of the plasmid. Both high plasmid copy numbers and a strong promoter (tac) are necessary to achieve the level of overproduction necessary for excretion of β‐lactamase, but high‐level target protein synthesis is detrimental to the cell. A derivative of pKN which is more easily regulated was constructed by adding the lacl gene to the plasmid.
Simultaneous Biodegradation of Toluene and p‐Xylene in a Novel Bioreactor: Experimental Results and Mathematical Analysis
Authors: Lee Jang‐Young , Choi Yong‐Bok , Kim Hak‐Sung 
Published: March 2005

AbstractSimultaneous biodegradation of toluene and p‐xylene was performed in a novel bioreactor, and the performance was analyzed on the basis of both experimental and mathematical simulation results. The novel bioreactor employed a silicon tubing as a supplier of the aromatic solvents to be treated, and the transfer rate of toluene and p‐xylene into the culture broth was easily controlled. Batch, sequencing batch, and continuous mode of operation were carried out in the novel bioreactor to compare the performance of the biodegradation of solvent mixture. Sequencing batch operation worked well, but several operational difficulties were found. Continuous operation was shown to present higher biodegradation rates and operational stability. The continuous biodegradation process was mathematically simulated, and operational conditions were optimized on the basis of the simulation results.