bluuebunny/crossref_metadata_2025_split huggingface dataset:
Precipitation of Nucleic Acids with Poly (ethyleneimine)
Authors: Cordes Richard M. , Sims W. Bradley , Glatz Charles E. 
Published: March 2005

AbstractRemoval of nucleic acids from cell extracts is a common early step in downstream processing for protein recovery. We report on the precipitation of nucleic acids from a homogenate of Saccharomyces cerevisiae by addition of the cationic polyelectrolyte poly (ethyleneimine) (PEI), focusing on the effect of PEI dosage on particle size, protein loss, and extent of nucleic acid removal in both batch and continuous mode. Better than 95 % removal of nucleic acids from yeast homogenates was achieved by means of precipitation with PEI with protein losses of approximately 15% with or without previous removal of cell debris. The coprecipitated protein is predominately large molecular weight material and exhibits both low and high isoelectric points. Such treatment does not aggregate the cell debris; size distribution of the precipitated particles from a continuous precipitator is very similar to that for protein precipitation.
Separation of β‐Carotene Mixtures Precipitated from Liquid Solvents with High‐Pressure CO2
Authors: Chang Chiehming J. , Randolph Alan D. , Craft Neal E. 
Published: March 2005

AbstractSolids precipitation from liquid solvents, with dissolution by high‐pressure CO2 as an antisolvent to create supersaturation, is a potentially attractive crystallization process. Solids can be recrystallized and easily isolated from the liquid solvent. The gas antisolvent solvent (GAS) process was used to separate and purify β‐carotene from a mixture containing carotene oxidation products. Total β‐carotene was successfully separated from oxides, and an enriched traras‐β‐carotene was obtained from its cis isomers. The separation was carried out in both batch and continuous modes. Relative solubility of the analytes and the antisolvent (CO2) have a dramatic influence on the absolute yield and purity of the product.
Synergistic Response of Plant Hairy‐Root Cultures to Phosphate Limitation and Fungal Elicitation
Authors: Dunlop David S , Curtis Wayne R 
Published: March 2005

AbstractThe combined effects of phosphate limitation and fungal elicitation on sesquiterpene production were examined in Agrofeacterium‐transformed “hairy‐root” cultures of Hyo‐scyamus muticus Limiting the initial supply of inorganic phosphate to elicited cultures resulted in a 4.2‐fold increase in solavetivone production as compared to elicitation at control media phosphate levels (1.1 mM). Because growth was attenuated at low initial phosphate levels, production per unit cell mass increased 46 times as compared to the control. Both elicited and nonelicited cultures showed enhanced solavetivone production at lower initial phosphate levels. In fact, the specific productivity of nonelicited roots grown in phosphate‐free media was comparable to the specific productivity of fungally elicited roots that are not phosphate limited. Addition of fungal elicitors enhanced specific productivity of solavetivone about 200‐fold over nonelicited cultures at nearly all phosphate levels. Phosphate limitation and fungal elicitation are therefore synergistic, and optimal total production is achieved by simultaneous application of these two production strategies.
Filtration Properties of Mycelial Microbial Broths
Authors: Oolman Timothy , Liu Tuan‐Chi 
Published: March 2005

AbstractThe filtration properties of three mycelial cultures (Streptomyces griseus, Streptomyces tendae, and Penicillium chrysogenum) have been measured and quantified in terms of standard filtration equations. Three of the filtration parameters, the hyphal density, the index of compressibility, and the Kozeny constant, were found to vary systematically with broth age and with the visually observed morphology (i.e., pellets vs filaments). Since broth age and mycelial morphology both have a strong influence on bioreactor productivity, it is suggested that filtration could be used for on‐line monitoring of mycelial fermentations.
Effects of Oxygen and Carbon Dioxide Partial Pressures on Monascus Growth and Pigment Production in Solid‐State Fermentations
Authors: Han Ohantaek , Mudgett Richard E. 
Published: March 2005

AbstractLevels of oxygen and carbon dioxide in the gas environment were found to influence pigment production significantly and growth to a lesser extent in solid‐state fermentations with Monascus purpureus on rice. Maximum pigment yields were observed at 0.5 atm of oxygen partial pressure in closed pressure vessels. However, high carbon dioxide partial pressures progressively inhibited pigment production, with complete inhibition at 1.0 atm. In a closed aeration system with a packed‐bed fermentor, oxygen partial pressures ranging from 0.05 to 0.5 atm at constant carbon dioxide partial pressures of 0.02 atm gave high pigment yields with a maximum at 0.50 atm of oxygen, whereas lower carbon dioxide partial pressures at constant oxygen partial pressures of 0.21 atm gave higher pigment yields. Maximum oxygen uptake and carbon dioxide evolution rates were observed at 70–90 and 60–80 h, respectively, depending on the gas environment. Respiratory quotients were close to 1.0, except at 0.05 atm of oxygen and 0.02 atm of carbon dioxide partial pressures. Optimum conditions for pigment formation were generally not the same as those for growth.
Ellipsometric Evaluation of β‐Lactoglobulin Adsorption onto Low‐and High‐Energy Materials
Authors: Al‐Malah Kamal , Mcguire Joseph , Krisdhasima Viwat , Suttiprasit Prasert , Sproull Robert 
Published: March 2005

AbstractEllipsometry was used to study solid‐surface energetic and temperature effects on the apparent equilibrium adsorptive behavior exhibited by β‐lactoglobulin. Adsorption isotherms were constructed for β‐lactoglobulin on seven different silicon surfaces chemically modified to exhibit varying hydrophobicities: plateau values of adsorbed mass were observed to increase with increasing degree of solid‐surface silanization with dichlorodimethylsilane. β‐Lactoglobulin isotherms at 2,27, and 52°C were constructed on unsilanized and completely silanized silicon surfaces: adsorbed mass increased upon increasing temperature beyond 2°C, but no difference was observed between isotherms drawn at 27 and 52°C for either surface. Isotherms were then constructed for acrylic, polycarbonate, polyester, glass, and no. 304 stainless steel surfaces at 37 and 55°C. In all cases, optical properties of the protein films were ellipsometrically measured and their adsorbed mass was calculated from film thickness and refractive index. The protein adsorption results recorded for the polymer, glass, and stainless steel surfaces could not be explained with reference to solid‐surface hydrophobicity alone. For polymers, adsorbed mass is suggested to be related to the extensibility of molecular structure at the surface. Glass was observed to adsorb the greatest mass of β‐lactoglobulin, and no. 304 stainless steel the lowest; however, glass and the polymers, being transparent, presented a different optical problem for ellipsometry compared to that posed by silicon and stainless steel. A temperature dependence of β‐lactoglobulin adsorption was not observed between 37 and 55°C, probably due in part to the temperatures studied having been below the denaturation temperature of β‐lactoglobulin, as indicated by differential scanning calorimetry.
Posttranslational Limitations to Methanol Oxidase Activity in the Methylotrophic Yeast Hansenula polymorphs As Determined from Single Growth Rate Perturbations
Authors: Bryers J. D. , Westcott R. W. , Sayles G. D. 
Published: March 2005

AbstractSingle shifts in growth rate were imposed upon continuous cultures of the methylotrophic yeast Hansensula polymorpha growing under carbon limitation on 4 g/L methanol and 1 g/L glucose. Concentrations of system level parameters (glucose, methanol, and cell biomass) and intracellular components (methanol oxidase and hex‐okinase specific activity, methanol oxidase specific mRNA content, and the ratio of flavin adenine dinucleotide bound to methanol oxidase) suggest that the reduction in methanol oxidase specific activity upon a shift to a higher growth rate is limited, not at the transcription level, but rather posttranslationally during peroxisome assembly. Subsequent [35S] methionine pulse‐chase techniques and immunoprecipitation of methanol oxidase monomers and octamers indicate, upon a dilution rate shift from 0.2 to 0.35 h−1, that monomeric methanol oxidase fails to polymerize, terminating peroxisome formation. Those peroxisomes formed at the lower growth rate slowly disintegrate at the higher growth rate, releasing bound flavin adenine dinucleotide.
Acoustic Resonances in Chicken Eggs
Authors: Sinha Dipen N. , Johnston Roger G. , Grace W. Kevin , Lemanski Cheryl L. 
Published: March 2005

AbstractWe report the first acoustical vibration studies on chicken eggs. Measurements of the acoustic resonances offer the potential of simple, noninvasive, and rapid characterization of eggs. The technique appears at least partially sensitive to yolk puncture, shell cracks, and the presence of Salmonella bacteria. There may be practical quality control applications.
Use of Monoclonal Anti‐enzyme Antibodies for Analytical Purposes
Authors: Gunaratna P. Chandrani , Wilson George S. 
Published: March 2005

AbstractThis review discusses the analytical applications of monoclonal antibodies specific for enzymes. One important, but not well‐studied, application of these monoclonal antibodies is their use in immobilizing enzymes on solid supports. This method is based on binding the enzymes to an immobilized antibody through the antigen bindng site of the antibody. Enzymes immobilized this way retain much of their activity. The utility of immobilized enzyme reactors prepared by immobilizing the enzymes through antibodies is demonstrated by using them in the determination of acetylcholine and choline in brain tissue extracts. Currently available methods for immobilizing antibodies and enzymes are reviewed. Other issues discussed in this review include the problems and advantages of immobilized enzyme reactors, especially when used in conjunction with HPLC. In addition, the applications of monoclonal antibodies for the detection and measurement of enzymes and their isoforms are summarized.
Spatial Distribution of Mammalian Cells Grown on Macroporous Microcarriers with Improved Attachment Kinetics
Authors: Lim Hyun‐Soo , Han Bong‐Kwan , Kim Jung‐Hoe , Peshwa Madhusudan V. , Hu Wei‐Shou 
Published: March 2005

AbstractVero and HepG2 cells were cultivated on macroporous gelatin microcarriers prepared by the calcium carbonate inclusion method. Cell attachment to these microcarriers was slow. For HepG2 cells the subsequent growth was poor. Modification of the microcarriers by incorporation of (diethylamino)ethyl‐HCl improved HepG2 attachment and subsequent growth. Optical sectioning with confocal microscopy allowed visualization of the distribution of cells within microcarriers. In most microcarriers, cells were found to preferentially populate regions close to the external surface and some cavities in the interior. Despite the incomplete occupancy of the interior of the microcarriers, high cell concentrations were achieved.
Isolation of Vindoline from Catharanthus roseus by Supercritical Fluid Extraction
Authors: Song Kyu‐Min , Park Sang‐Woo , Hong Won‐Hi , Lee Huen , Kwak Sang‐Soo , Liu Jang‐Ryol 
Published: March 2005

AbstractVindoline was extracted from the leaves of Catharanthus roseus over the ranges of 35–70 °C and 100–300 bar using supercritical carbon dioxide with and without the addition of 3 wt % ethanol as a cosolvent. The vindoline contents in the extracts were determined by HPLC and identified by LC/MS. The remarkable highest vindoline concentration, 58 wt %, was obtained at the lowest temperature, 35 °C, and the highest pressure, 300 bar, of this study. The use of a cosolvent only slightly improved the extraction yields or selectivities at some experimental conditions.
TOPICAL PAPER: Utilization of Hairy Root Cultures for Production of Secondary Metabolites
Authors: Toivonen Leena 
Published: March 2005

AbstractThe possibility of producing useful chemicals by plant cell cultures has been studied intensively for the past 30 years. However, problems associated with low product yields and culture instabilities have restricted wider industrial application of plant cell culture. The employment of hairy root culture technology, developed in the past 10 years, offers new opportunities for in vitro production of plant secondary metabolites. In contrast to cell suspension cultures, hairy root cultures are characterized by high biosynthetic capacity and genetic as well as biochemical stability. In this review, the establishment and cultivation of hairy root cultures as well as their properties and application for production of secondary metabolites are discussed.
Performance of a Packed Column for Continuous Supercritical Carbon Dioxide Processing of Anhydrous Milk Fat
Authors: Bhaskar Ajay R. , Rizvi Syed S. H. , Harriott Peter 
Published: March 2005

AbstractA continuous system was designed for the processing of anhydrous milk fat (AMF) with supercritical carbon dioxide (SC‐CO2). The packed column was operated as a stripping column with SC‐CO2 as the continuous phase and AMF as the dispersed phase. The extraction was studied at 24.1 MPa and 40 °C. To utilize the functional similarities and make the analysis simpler, the AMF triglycerides were grouped as low‐melting (LMT: C24–C34), medium‐melting (MMT: C36–C40), and high‐melting triglycerides (HMT: C42–C54). There was an increase in the concentrations of LMT and MMT and a decrease in that of HMT in the extract. The raffinate has a high concentration of HMT with trace amounts of LMT. The performance characteristics of the packed column were described by the number of transfer units (Nog), the overall volumetric mass transfer coefficient (KOGa), and the height of a transfer unit (HOG). The NOG and Kogci values decreased and the HOG value increased with increasing solvent‐to‐feed ratio. The HOG values increased and the NOG and KOGa values decreased from LMT to MMT to HMT, but the HOG values for HMT were greater than expected. The values of NOG, HOG, and KOGa for AMF (as a single component) were intermediate to those of MMT and HMT.
Characteristics of Batch Suspension Cultures of Preconditioned Coleus blumei Cells: Sucrose Effect
Authors: Martinez Blanca C. , Park Chang‐Ho 
Published: March 2005

AbstractBatch suspension cultures of Coleus blumei cells preconditioned with 0.1% dimethyl sulfoxide (DMSO) maintained viability at above 85 % during a 14‐day culturing period for initial sucrose concentrations of 30–70 g/L. At 60 g/L sucrose, cells grew rapidly with a doubling time of 10.7 h, and dry cell mass reached a maximum of 15.6 g/L. Broad optima of cell yield (0.46–0.48 g of cell/g of sucrose), rosmarinic acid (RA) yield (3.1–3.5 g of RA/100 g of sucrose), and rosmarinic acid production (1.0–1.1 g of RA/L) were observed at 40–60 g/L sucrose concentration. Sucrose in the medium was hydrolyzed to glucose and fructose by extracellular and/or cell‐bound invertase, and glucose was taken up by the cells at a higher rate than fructose. Even at sucrose concentrations of 40–70 g/L, sucrose consumption over 14 days was limited to 33 g/L.
Extraction of Cytochrome c in Sodium Dodecylbenzenesulfonate Microemulsions
Authors: Jolivalt Claude , Minier Michel , Renon Henri 
Published: March 2005

AbstractThe partition of cytochrome c between an aqueous phase in equilibrium with a microemulsion composed of sodium dodecylbenzenesulfonate, butanol, and decane was studied. By adjusting the pH and the ionic strength in the aqueous phase, cytochrome c can be quantitatively extracted in the microemulsion as long as the protein concentration in the organic phase is less than the initial concentration of micelles. Above this limit, an intermediate phase, containing part surfactant and part cytochrome c, is located between the aqueous and microemulsion phases. The role of electrostatic interactions in the protein partitioning is shown by varying the composition of the phases (pH, salinity, surfactant, and cosurfactant concentrations) and then discussed. Extraction depends on the relative values of the pH of the aqueous phase and the pI of cytochrome c, the size of the micelles, and the protonation of acidic residues. Cytochrome c can be recovered in an aqueous phase by adding butanol in the microemulsion phase. In such conditions, cytochrome c retains 90% of its initial activity, as measured before the extraction step.
Utilization of Microwaves in the Study of Reaction Kinetics in Liquid and Semisolid Media
Authors: Welt B. A. , Steet J. A. , Tong C. H. , Rossen J. L. , Lund D. B. 
Published: March 2005

AbstractAn apparatus, referred to as the microwave kinetics reactor (MWKR), incorporating a microwave‐transparent pressure vessel with mechanical mixing together with a microwave temperature controller, was developed and tested. Experiments were performed to determine a safe and practical operating envelope for the MWKR. Temperatures measured at the center and at the top surface of varying viscosity solutions in the MWKR were used to determine the adequacy of mixing when the solutions were heated from room temperature to 120 °C and held for a prescribed period of time. The viscosities of the solutions were adjusted by adding (carboxymethyl)cellulose (CMC) to distilled water. A 2% CMC solution represented the upper viscosity limit to be heated homogeneously in the apparatus (approximately 2000 cP). To illustrate the usefulness of this apparatus in obtaining kinetic parameters, thiamin hydrochloride degradation kinetics in pea puree were determined at 100, 120, and 130 °C and compared to those obtained from the literature. The MWKR offers an attractive, efficient, convenient, and accurate alternative for the study of reaction kinetics in viscous fluids and semisolids because of its short come‐up time and mixing capability. Experimentally determined kinetic parameters compared very well to those obtained from the literature. As expected the kinetics was first‐order, with an activation energy, Ea, of 27.0 kcal/mol.
Molecular Characterization of β‐Lactamase Inclusion Bodies Produced in Escherichia coli. 1. Composition
Authors: Valax Pascal , Georgiou George 
Published: March 2005

AbstractWe have determined the macromolecular composition of inclusion bodies formed by overexpressing β‐lactamase from three different expression systems as a function of the growth conditions. The inclusion bodies were purified by differential gradient centrifugation and detergent extraction. Both the expression system and the growth conditions were shown to have a pronounced effect on inclusion body composition. Specifically, contaminating polypeptides ranged from less than 5% to over 50% of the total protein content. Phospholipids composed 0.5–13 % of the inclusion bodies. Nucleic acids represented a minor impurity for both cytoplasmic and periplasmic inclusion bodies. Cytoplasmic inclusion bodies of the mature β‐lactamase had the lowest amount of impurities, irrespective of the growth conditions. On the other hand, large amounts of outer membrane proteins and phospholipids were observed in periplasmic inclusion bodies from cells grown at basic pH. Our results show that, at least under some growth conditions, protein aggregation in vivo is highly specific, and the presence of contaminating proteins in inclusion bodies is due to incomplete purification following cell lysis.
Effects of the par Locus on the Growth Rate and Structural Stability of Recombinant Cells
Authors: Kim Jeong‐Yoon , Kang Hyun Ah , Ryu Dewey D. Y. 
Published: March 2005

AbstractA decreased growth rate of recombinant cells is observed when a cloned gene protein encoded in a multicopy plasmid is induced from a strong promoter. This negative effect on the cell growth rate may be the consequence of alternate use or reallocation of energy, precursor metabolites, and protein synthesizing machinery. In order to analyze the causes for this adverse effect, we have studied how genetic elements present in multicopy plasmids affect the growth ofrecombinant Escherichia coli (K12ΔH1 ΔtrpEA). Turning on of the PL promoter, whether or not protein‐coding sequences were present downstream of the promoter, decreased the growth of the recombinant cells by 15–50 %. This result suggests that the essential factor(s) for cell growth may be sequestered by the genetic elements present in the plasmids and thus may cause the decreased growth. The negative effect of the de‐repressed PL promoters on cell growth was partially reversed when the par sequence from pSC101 was inserted into the same plasmid. In each case when the plasmid carried only the PL promoter, the PL promoter followed by the N‐terminal part of the protein‐coding region, or the PL promoter followed by complete sequences encoding a protein, the par sequence exhibited a positive effect on the growth rate of the recombinant cells, which usually grow at a slower rate than the host cell. In addition, it was found that the recombinant cells bearing the plasmid with the par locus were as resistant as the host cell to osmotic shock when exposed to distilled water, whereas the recombinant cells bearing the plasmid without the par locus were sensitive to osmotic shock and resulted in lysis.
Copy Number Modulation in an Autoselection System for Stable Plasmid Maintenance in Saccharomyces cerevisiae
Authors: Compagno C. , Tura A. , Ranzi B. M. , Alberghina L. , Martegani E. 
Published: March 2005

AbstractEfficient expression of a foreign gene requires a stable vector present at a high number of copies per cell. We have constructed an autoselection system for the stable maintenance of expression vector in the yeast Saccharomyces cerevisiae that uses the fructose 1, 6‐bisphosphate aldolase gene (FBA1) to stabilize plasmids in cells bearing a disruption of the chromosomal FBA1 gene. This system allowed us to obtain stable production of a reporter heterologous enzyme (Escherichia coli β‐galactosidase) in rich media. By using an inducible promoter to regulate the expression of FBA1 gene, we have also obtained the modulation of plasmid copy number by carbon source.
Growth versus Function in the Three‐Dimensional Culture of Single and Aggregated Hepatocytes within Collagen Gels
Authors: Parsons‐Wingerter Patricia A. , Saltzman W. Mark 
Published: March 2005

AbstractHepatocytes require cell—cell and cell—substrate interactions to survive and function. Furthermore, cell proliferation and differentiated function are often reciprocally related activities, both of which are highly regulated in the liver microenvironment. To mimic the physiological organization of hepatocytes into multicellular plates, small hepatocyte aggregates containing an average of 4–6 cells were formed. The aggregates were suspended within three‐dimensional collagen gels and compared to both single hepatocytes (suspended within collagen gels) and hepatocyte monolayers (on tissue culture polystyrene) over 6 and 10 days in culture. The comparison of aggregates with single cells represents a novel in vitro system for the study of hepatocyte cell‐cell interactions. All hepatocyte‐populated gels displayed almost identical patterns of cell behavior: hyperplastic or hypertrophic growth (indicated by DNA or protein concentration) coincided with the decline of phenotypic function (assessed by uric acid and albumin production), while functional recovery often accompanied the cessation of growth. However, aggregate cultures maintained an average of 2‐fold higher concentrations of functional parameters than singlet cultures when cells were not involved in growth activities. Much higher concentrations of all cell parameters were sustained by gel‐dispersed hepatocytes than by hepatocyte monolayers.