bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of pBR322 replication kinetics and its dependency on growth rate
Authors: Kim Byung Gee , Shuler M. L. 
Published: May 2005

AbstractAccurate estimates of plasmid copy number in a cell are a prerequisite for predicting plasmid stability and protein production. A refined version of a structured model for the pBR322 plasmid replication mechanism is described. The model is capable of accurately predicting pBR322 plasmid copy number in Escherichia coli B/r for a wide range of growth rates. The refinements include better estimates of promoter strength, the degradation rate of RNA species, binding constant of RNAI–RNAII reaction, and dependency of promoter strength on growth rate. The predictions of the model are verified by recent experimental observations but differ from some previous reports. This model can also be used to predict the binding constant of the RNAI–RNAII reaction of ColE1 type plasmids. At 37°C, the binding constant is estimated to be 77 ± 11 × 10−13 mL/molecule‐h for pBR322.
Product deactivation in recombinant Streptomyces
Authors: Gardner Alan R. , Cadman T. W. 
Published: May 2005

AbstractThe production of tyrosinase by Streptomyces antibioticus (p1J7O2) was investigated as a model system for recombinant protein production by Streptomyces. Product deactivation was found to have a severe effect on the levels of tyrosinase obtained. Tyrosinase deactivation was detected during all phases of batch cultures, with higher specific deactivation rates observed during the stationary phase. The specific deactivation rate exhibited an Arrhenius dependence on temperature, with approximately a twofold increase in the deactivation rate between 25°C and 30°C. The effect of deactivation on the determination of tyrosinase production kinetics is discussed. A strategy was implemented to increase tyrosinase productivity by enriching the growth medium and reducing the culture temperature during the period of maximum tyrosinase production. This strategy resulted in a shorter culture time and a 2.5‐fold increase in tyrosinase activity compared to a culture grown at 25°C using a standard growth medium.
Involvement of a cell size control mechanism in the induction and maintenance of oscillations in continuous cultures of budding yeast
Authors: Martegani Enzo , Porro Danilo , Ranzi Bianca Maria , Alberghina Lilia 
Published: May 2005

AbstractSpontaneous oscillations occur in glucose‐limited continuous cultures of Saccharomyces cerevisiae under aerobic conditions. The oscillatory behavior is detectable as a periodic change of many bioparameters such as dissolved oxygen, ethanol production, biomass concentration, as well as cellular content of storage carbohydrates and is associated to a marked synchronization of the yeast population. These oscillations may be related to a periodic accumulation of ethanol produced by yeast in the culture medium.The addition of ethanol to oscillating yeast cultures supports this hypothesis: indeed, no effect was observed if ethanol was added when already present in the medium, while a marked phase oscillation shift was obtained when ethanol was added at any other time. Moreover, the addition of ethanol to a nonoscillating culture triggers new oscillations. An accurate analysis performed at the level of nonoscillating yeast populations perturbed by addition of ethanol showed that both the growth rate and the protein content required for cell division increased in the presence of mixed substrate (i.e., ethanol plus limiting glucose). A marked synchronization of the yeast population occurred when the added ethanol was exhausted and the culture resumed growth only on limiting glucose. A decrease of protein content required for cell division was also apparent. These experimental findings support a new model for spontaneous oscillations in yeast cultures in which the alternative growth on limiting glucose and limiting glucose plus ethanol modifies the critical protein content required for cell division.
Enhanced shikonin production from Lithospermum erythrorhizon by in situ extraction and calcium alginate immobilization
Authors: Kim Dong Jin , Chang Ho Nam 
Published: May 2005

AbstractPlant cell cultures of Lithospermum erythrorhizon were carried out to produce shikonin by in situ extraction and cell immobilization in calcium alginate bead in shake flask cultures. In situ product extraction and cell immobilization enhanced shikonin production and facilitated product recovery. In situ extraction by n‐hexadecane and cell immobilization by calcium alginate gave higher specific shikonin productivities of 7.4 and 2.5 times, respectively, than those from the cultures of free cells without extraction. Simultaneous use of both techniques increased specific and volumetric productivities of shikonin 25‐ and 15‐fold, respectively. In calcium alginate immobilized cell cultures, n‐hexadecane addition at an early stage (before 15 days) was effective for shikonin production, and solvent addition after 15 days of the culture significantly reduced shikonin production. Higher numbers of plant cell immobilized bead inoculation did not increase shikonin production and sucrose consumption. Most of the produced shikonin was dissolved in the solvent layer.
Theoretical development and performance evaluation for extractive fermentation using multiple extractants
Authors: Shi Zhongping , Shimizu Kazuyuki , Iijima Shinji , Morisue Toshiya , Kobayashi Takeshi 
Published: May 2005

AbstractMathematical formulation was made for the performance evaluation of extractive fermentation using multiple solvents. Two types of solvent‐supplying strategies were considered. One is to add multiple solvents simultaneously and the product is removed at one time. Another is to add them one by one consecutively. Computer simulation was made for batch, fed‐batch, and repeated fed‐batch operation of acetone–butanol fermentation to show the power of the approach. The result shows that the significant performance improvement in terms of the productivity and the product concentration is expected when two extractants such as oleyl alcohol and benzyl benzoate are used as compared with the case of using only one solvent.
Transient shear stresses on a suspension cell in turbulence
Authors: Cherry Robert S. , Kwon Kei‐Young 
Published: May 2005

AbstractA model flow field representative of Kolmogorov eddies in turbulence is proposed, and its two parameters are expressed in terms of the known bioreactor variables ε, the rate of turbulent power dissipation, and ν, the fluid kinematic viscosity. The trajectory through this flow field of a small sphere representing a cell is determined, and from that the time‐varying local shear rate can be found. This allows calculation of the shear stress at any point on the sphere's surface as it rotates in and moves through the model eddy. The maximum shear stress imposed on the cell by the surrounding turbulence has a range of 0.5–5 dyn/cm2, and can be estimated by 5.33ρ(εν)1/2. The shear stress has two major frequency components with ranges of 1–4 and 20–80 s−1; the higher frequency component is estimated by 0.678(ε/ν)1/2. The rotation of the direction of the shear stress vector at each point on the cell's surface is also discussed. Two ways in which external stresses might affect cell growth are proposed.
Optimization of a pellicular biocatalyst for penicillin G production by Penicillium chrysogenum
Authors: Flanagan William P. , Klei Herbert E. , Sundstrom Donald W. , Lawton Carl W. 
Published: May 2005

AbstractA previously developed immobilization technique involving latex coatings on solid particulate supports was investigated further for penicillin G production by Penicillium chrysogenum. Several modifications were found to decrease the germination lag time, including a higher spore concentration, a thinner latex layer, an increased latex porosity, and a decreased drying time. This approach enabled the development of immobilized mycelial pellets within 2–3 days from the onset of biocatalyst preparation and incubation.A continuous immobilized‐cell airlift bioreactor produced penicillin G in a series of runs in which the production phase lasted up to 30 days. The productivity of this system was 3–6 times greater than the productivity of the corresponding free‐cell shake flask fermentation.
Continuous hydrolysis of oil by immobilized lipase in a countercurrent reactor
Authors: Kosugi Yoshitsugu , Tanaka Hideoki , Tomizuka Noboru 
Published: May 2005

AbstractLipase from Pseudomonas fluorescens biotype I was immobilized by adsorption of anion exchange resin using glutaraldehyde to enhance the adsorption. The activity yield of the immobilized lipase was very low (below 1%) when lipase activity was measured using emulsion substrate. The activity yield was 10–70% when lipase activity was measured using non‐emulsion substrate. Countercurrent reactors for hydrolysis of oil using non‐emulsion substrate were studied. A fluidized bed reactor was found to be superior to a fixed bed one since in a fixed bed reactor the separation rate of the two layers was slow and the flow rate of the reactor had to be slower than the separation rate. A fluidized bed reactor system equipped with settling compartments and stirring compartments was devised. Continuous lipolysis at 60 °C and continuous separation of oily product and water soluble product were performed. After continuous operation for more than 3 months, 70% of the initial activity of the immobilized lipase was observed at the end of the reaction.
Continuous production of maltotetraose using a dual immobilized enzyme system of maltotetraose‐forming amylase and pullulanase
Authors: Kimura Takashi , Ogata Masafumi , Kobayashi Haruto , Yoshida Masahiro , Oishi Kayoko , Nakakuki Teruo 
Published: May 2005

AbstractIn order to produce a product with a high content of maltotetraose, dual‐enzyme systems composed of immobilized maltotetraose‐forming amylase (G4‐forming amylase) and pullulanase were studied. The thermostability of individually immobilized enzymes was examined in continuous operation; studies revealed that the enzyme immobilized on “Chitopearl” was much more stable than that immobilized on Diaion HP‐50. The effects of operating conditions on the stability of G4 forming amylase immobilized on “Chitopearl” were examined to confirm that the apparent half‐life data could be arranged using the immobilized enzyme stability factor, fs. As for the dual immobilized enzyme system, six methods of usage were considered, with five yielding a 7–10% (w/w) higher content of maltotetraose product than the single‐enzyme system. The effects of operating conditions on the maltotetraose production reaction were examined to confirm that the maltotetraose content of the products could be analyzed using the specific space velocity,SSV. In dual immobilized enzyme systems, pullulanase immobilized on the same carrier as the G4‐forming amylase was found to be more stable than pullulanase immobilized on separate carriers. The effectiveness of using immobilized pullulanase along with the G4‐forming amylase was confirmed from constant‐conversion operations in which the maltotetraose content in the product was kept at 50% (w/w) in laboratory‐scale experimentation.
The process utility of thermotolerant methylotrophic bacteria: I. An evaluation in chemostat culture
Authors: Al‐Awadhi Nader , Egli Thomas , Hamer Geoffrey , Mason C. Anthony 
Published: May 2005

AbstractIn Part l, the process utility of a thermotolerant methylotrophic bacterium is evaluated in chemostat culture under conditions where methanol, methanol/formaldehyde mixtures and dual methanol/ammonia limitation occurred. The results show that the bacterium studied was nonfastideous under steady‐state operation, in contrast to results obtained in batch culture. For application in industrial wastewater treatment processes the bacterium should be employed in systems where the biomass residence time exceeds 5 h, i. e., dilution rates < O.2 h−1. Under such conditions, methanol was essentially exhausted and the biomass yield coefficient was lowered.
Cell cycle‐ and growth phase‐dependent variations in size distribution, antibody productivity, and oxygen demand in hybridoma cultures
Authors: Ramirez Octavio T. , Mutharasan R. 
Published: May 2005

AbstractSimultaneous determination of cell size and DNA content of hybridomas (HB‐32) revealed a direct correlation between average cell volume and progression through the cell cycle. Pseudocontinuous experiments showed that G1 cells, as estimated from cell size measurements, secreted monoclonal antibody at rates higher than those of cells in other stages of interphase and mitosis. Similarly, fed‐batch and batch experiments suggested that specific oxygen uptake rate (qO2) is also a function of cell cycle, being minimum for cells in G0 and G1 phase. In batch cultures, HB‐32 showed a rapid decrease in oxygen uptake rate (OUR) just prior to reaching maximum cell concentration. The OUR steadily increased from 0.01–0.05 to 0.5–0.7 mmol O2/L h as the cells went from the lag to the midexponential phase. The qO2 increased from 0.3 × 10−10−0.9 × 10−10 mmol O2/cell h at inoculation to 3.3 × 10−10−3.7 × 10−10 mmol O2/cell h during the early exponential phase where it remained relatively constant. Several hours before maximum cell concentration was reached, OUR and qO2 rapidly decreased to levels below those observed at inoculation. The time at which the shift in OUR and qO2 occurred and the onset of decrease in the average cell size corresponded to the time of glutamine depletion. Based on monitoring OUR on‐line in batch cultures, glutamine was supplemented, resulting in increased cell concentration, extension of culture viability, and increased MAb concentration.
Micro‐scale sequence analysis from the N‐terminus of peptides using the fluorogenic edman reagent 4‐N, N‐dimethylamino‐1‐naphthyl isothiocyanate
Authors: Miyano Hiroshi , Nakajima Terumi , Imai Kazuhiro 
Published: May 2005

AbstractThe fluorogenic Edman reagent 4‐N,N‐dimethylamino‐1‐naphthyl isothiocyanate (DNTC) was reacted with amino acids and peptides, cyclized by acid and the liberated 4‐N,N‐dimethylamino‐1‐naphthyl thiohydantoin (DNTH) amino acids were then separated and detected by HPLC. The fluorescence intensities of DNTH‐amino acids except DNTH‐proline and ‐serine were dramatically increased in the alkaline solution and organic solvent. Thus, the postcolumn reaction with alkaline acetonitrile solution was adopted in HPLC. The polar and aromatic amino acids afforded two DNTH‐amino acids on derivatization with DNTC and cyclization with acids. These were suggested to be stereoisomers of DNTH‐amino acids. The sequence analysis of 0.5 nmol Leu‐enkephalin was achieved by the double coupling method with DNTC and phenyl isothiocyanate followed by the proposed HPLC system.
Determination of plasma cytidine deaminase activity by HPLC
Authors: Richards D. A. , Sherwood R. A. , Ndebele D. , Rocks B. F. 
Published: May 2005

AbstractCytidine deaminase is an enzyme of nucleic acid metabolism, the measurement of which has been proposed as a useful test for the early detection of pre‐eclamptic toxaemia in pregnancy. The enzyme converts the nucleoside cytidine to uridine, with the release of ammonia, and it is the measurement of this latter compound that forms the basis of the conventional methods for the assay of cytidine deaminase. The low activity of the enzyme requires long incubation times, which in turn increase the possibility of contamination by exogenous ammonia. We have developed a new method for determining cytidine deaminase activity, utilising high performance liquid chromatography to measure the production of uridine. This method uses much shorter incubation times and is unaffected by ammonia contamination. This paper describes the development of the method and its comparison with the established assay. The relative merits of each are discussed. Finally, the adaptation of incubation and chromatographic conditions, in order to measure other enzymes of nucleic acid metabolism which are of clinical interest, is briefly mentioned.
Mobile phase versus stationary phase approaches to the direct injection of biological fluids in liquid chromatography
Authors: Fett Joseph J. , Hischak Frank , Love L. J. Cline 
Published: May 2005

AbstractThe liquid chromatographic analysis of drugs in urine through direct injection without any sample pretreatment was extended to micellar chromatography with nonionic surfactants, the Pinkerton™ ISRP column and the shelded hydrophobic phase (Hisep™) column. The feasibility of using each was demonstrated through the determination of the diuretic, hydrochlorothiazide, in urine. Good separation, recovery, precision and linearity, and adequate limits of detection were obtained for this analysis with all three techniques. The advantages and limitations of the mobile phase approach of micellar chromatography and the two stationary phase approaches are discussed for the direct injection of urine as well as other biological fluids.
A mixed‐bed, multi‐derivatization approach using polymeric reagents for derivatizations of amines in high performance liquid chromatographic detection
Authors: Gao Chun Xin , Schmalzing Dieter , Krull Ira S. 
Published: May 2005

AbstractImmobilized, polymeric reagents containing covalently attached tagging groups have been synthesized and reacted individually, off‐line or on‐line, pre‐column in high performance liquid chromatographic (HPLC) detection. These reagents have also been combined into a single, mixed‐bed reactor, useful for simultaneously preparing several derivatives from a single analyte, all at the same time. Each derivative possesses different chromatographic and detection properties, dependent on the nature of the original polymeric reagent containing the immobilized, tagging species. These particular reagents were designed to impart Ultraviolet/fluorescence, Ultraviolet/electrochemistry (oxidative/reductive or oxidative‐hv‐electrochemistry) to the final derivatives. Variations in the amounts/ratios of polymeric reagents contained in a single mixed‐bed reactor will lead to varying ratios of the final derivatives. These can be predicted knowing the approximate reactivity of each polymeric reagent, percent derivatizations, and overall rates for each reagent towards a given substrate. In this first example of mixed‐bed, polymeric reagents for improved derivatization approaches in chromatography, emphasis has been placed on simple amines or amine‐like analytes. Multiple derivatives can be effectively used to improve the identification of an unknown analyte in a complex sample matrix, as well as to improve the detectability of that analyte. As one real world application, amphetamine in human urine was quantitated via on‐line derivatizations‐with a mixed‐bed reactor. With the least sampling work‐up, the resulting sample solutions were directly injected into the on‐line derivatization HPLC system for quantitation. The method was validated by single blind spiking experiments. The precision and accuracy were acceptable.
High performance liquid chromatographic determination of individual bile acids in serum for automatic diagnosis of various liver and biliary diseases
Authors: Zhao R. H. , Li B. Y. , Chen N. , Zhang Y. K. , Wang Z. Y. , Lu P. C. 
Published: May 2005

AbstractA reversed phase high performance liquid chromatographic method for the high sensitivity determination of individual bile acids in serum using a C18 column with a ternary solvent system combined with fluorometric techniques using immobilized enzymes is described. A computer‐assisted diagnosis system using pattern recognition was developed to assist the clinical diagnosis of various liver and biliary diseases. A total consistency rate of 95% can be reached using this system.
Combined reversed phase and anion exchange solid phase extraction for the assay of the neuroprotectant NBQX in human plasma and urine
Authors: Ingwersen Steen H. 
Published: May 2005

AbstractA combination of reversed phase and anion exchange solid phase extraction (SPE) was investigated for the liquid chromatographic assay of the neuroprotectant agent NBQX in human plasma and urine. Reversed phase SPE alone using a variety of phases failed to yield sufficiently pure extracts for the assay of plasma in the low ng/mL concentration range using UV detection. However, using Bond Elut Certify IITM SPE columns containing a mixture of reversed phase and anion exchange functionalities markedly improved the purity of plasma extracts. Furthermore, a change of detector wavelength from UV (294 nm) to the visible region (380 nm) removed some minor interfering peaks originating from plasma. Using optimized SPE conditions with an extraction recovery of 92.3% and a high performance liquid chromatographic procedure with LichrospherTM C18 as the stationary phase, the lower limit of quantitation in human plasma was 2 ng/mL (corresponding to 0.75 ng injected on column). Intra‐assay coefficients of variation ranged from 9.6% at 2 ng/mL to 1.3% at 10 ng/mL. A similar SPE procedure was applied to human urine with acceptable recovery (88.3%), but an analytical column of different selectivity (ChromspherTM BC18) was necessary in order to avoid interference from the urine. The limit of quantitation for the urine assay was 25 ng/mL and the intra‐assay precision ranged from 4.6% at 25 ng/mL to 2.2% at 500 ng/mL.
Determination of catechol and guaiacol estrogens in urine by capillary gas chromatography/mass spectrometry
Authors: Saegusa Katsuhiko , Suzuki Emako , Anjo Takako , Matsuki Yasuhiko , Nambara Toshio 
Published: May 2005

AbstractA gas chromatographic (GC)/mass spectrometric method for the simultaneous determination in urine of 2‐ and 4‐hydroxyestrones and hydroxyestradiols, and their monomethyl ethers, is described. Separation of these catechol and guaiacol estrogens was achieved by derivatization into their trimethylsilyl and tert‐butyldimethylsilyl ethers, followed by capillary GC on a DB‐1 column. The calibration graphs were satisfactorily constructed for these estrogen metabolites by selected ion monitoring at the respective molecular ions using 2‐bromoestrone and 4‐hydroxyestradiol‐d3 3‐methyl ether as internal standards. The extraction and purification of the desired estrogens in biological fluids were effected by the combined use of Extrelut‐3 and ion exchange columns. The sensitivity and reliability obtained by the newly developed method has proved to be satisfactory for the quantiation of catechol and guaiacol estrogens in human urine.