bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of an on‐line commercial fluorescence probe: Modeling of the probe signal
Authors: Wang Nam Sun , Simmons Michael B. 
Published: December 2004

AbstractA biosensor model was developed for a commercial NADH fluorescence probe to describe the single‐frequency excitation and emission fluorescence behavior of an aqueous mixture of fluorophores. This model is essential in correlating the measured signals to the concentrations of fluorescent compounds in a bioreactor. In addition to the concentrations of fluorescent components, the relevant parameters of the model are the absorbance at both the excitation and the emission frequencies by the solvent and other absorbing species, the background signals, the light path length of the bioreactor vessel, the fluorescence yield, and the lampdetector configuration. Due to inner‐filter effects and other interferences, the probe signal is intrinsically nonlinear in both the fluorophore concentration and the path length. An important parameter in the model is the geometric constant, S, which accounts for variations in the monitoring efficiency throughout the sample because fluorescent light is emitted in all directions. Previous models, derived from an unrealistic assumption that fluorescent light is emitted only in one direction parallel to the probe axis, are shown to be seriously deficient. The validity of the model was verified experimentally for a single‐component solution in which both the fluorophore concentration and path length were varied.
Effect of alteration of the acetic acid synthesis pathway on the fermentation pattern of escherichia coli
Authors: Diaz‐Ricci J. C. , Regan L. , Bailey J. E. 
Published: December 2004

AbstractThe glucose metabolism of an Escherichia coli strain bearing mutations abolishing both acetyl phosphotransferase (PTA) and acetate kinase (ACK) activities was studied under aerobic and anaerobic conditions. These studies were conducted in a complex medium with the mutant carrying no plasmid, the mutant carrying the common cloning vector pUC19, and the mutant carrying a plasmid bearing the “pet” operon that encodes Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase activities. The mutant carrying no plasmid showed lower specific growth and glucose uptake rates relative to the parent wild‐type strain (K‐12), Lactic acid was produced at higher levels than the wild type, and considerable amounts of pyruvic acid were secreted as an unusual byproduct. Analysis of other fermentation products showed low but significant amounts of acetic acid, no accumulation of formic acid, and lower secretion of succinate and ethanol. The maintenance of the plasmid pUC19 in the mutant negatively affected metabolism. Expression of the pet operon overcame the metabolic stress caused by the plasmid, enhancing growth and glucose uptake rates to the values observed in the plasmidfree mutant. Also, expression of the pet operon allowed consumption of pyruvate accumulated during the first hours of fermentation.
Antigenic characteristics and stability of microencapsulated Mycoplasma hyopneumoniae vaccine
Authors: Lee C. J. , Tzan Y. L. 
Published: December 2004

AbstractThe in vitro stability (temperature, pH, and trypsin) of Mycoplasma hyopneumoniae antigen (MHA) with and without enteric‐coated microencapsulation were examined. Microencapsulation of MHA with cellulose acetate phthalate (CAP) is an effective route to produce enteric‐coated vaccine microspheres for oral administration. The effect of temperature on the rate of inactivation of MHA was studied by exposing MHA to various temperatures, such as 25, 37, 50 and 60°C. The MHA microspheres were thermally more stable than that of the unencapsulated MHA. The kinetic parameters were observed to follow an Arrhenius‐type temperature dependence. The MHA microspheres were also more stable in acidic regions (pH 1.2–4.0) than that of the free one. The enteric‐coated MHA microspheres exhibited an excellent enteric function to prevent acidic degradation. A model similar to the well‐known Michaelis‐Menten equation was formulated to describe the effect of trypsin on the antigenic degradation of MHA. The equilibrium constant KA and the maximum reaction velocity Vm were obtained from experimental data for both free and microencapsulated MHA. Both KA and Vm values of the microencapsulated MHA were smaller than that of the free one, i.e., the resistance to proteolytic enzyme such as trypsin was enhanced by microencapsulation. The storage stability of enteric‐coated MHA microspheres has been satisfactorily prolonged that they could preserve more than 90% of original antigenicity after 30 days, and over 80% of antigenicity of MHA was retained in the microspheres for 95 days when it was stored at 4°C.
Solute exclusion from cellulose in packed columns: Experimental investigation and pore volume measurements
Authors: Neuman R. P. , Walker L. P. 
Published: December 2004

AbstractA packed column approach was used in this investigation to determine pore volume and surface area distributions of several celluloses. Specific surface areas for Avicel PH 102, Solka Floc BW 300, and two size fractions of corn cobs that have been pretreated to remove lignin and hemicellulose were measured using this technique. In addition to measuring pore volume and specific surface area, the molecular diameters of several PEGs (polyethylene glycol) were estimated using viscosity measurements. Also, the influence of cellulose particle size, molecular diameter of PEGs, and PEG solution velocity on dispersion and tailing were investigated. Molecular diameter estimates from this investigation were 30%–35% lower than those reported in the literature. This discrepancy is due to earlier investigators using an inappropriate relationship for estimating molecular diameter from viscosity measurements. The precision of the column approach to solute exclusion was higher than that obtained by investigators using a batch approach. Dispersion increased with increasing particle size. Tailing of the elution curve was increased with increasing solute molecular diameter and elution rate. For a cellulase with a molecular diameter of 5.1 nm, estimated specific surface area ranged from 7.2 to 10.5 m2 g−1.
Calculation of thermodynamic properties of protein in Escherichia coli K‐12 grown on succinic acid, energy changes accompanying protein anabolism, and energetic role of ATP in protein synthesis
Authors: Battley Edwin H. 
Published: December 2004

AbstractUsing an average of the results from three methods of calculation, estimations are made of the thermodynamic properties of a unit carbon formula weight (UCFW) of Escherichia coli K‐12 protein. These resulted in values fro ΔGf of −38.09 kJ (−9.10 kcal)/ UCFW, for ΔHf of −68.18 kJ (−16.29 kcal)/UCFW, and for ΔSf of −94.2 J (−22.5 cal)/UCFW deg. The absolute entropy of one UCFW of E. coli K‐12 protein is calculated to be 73.8 J/UCFW deg. Using these values, the corresponding changes in thermodynamic properties accompanying the anabolism of protein by this microorganism to from one UCFW of protein by this microorganism to from one UCFW of protein are calculated to be 1.97 kJ (0.47 kcal)/UCFW for ΔG, 0.75 kJ (0.18 kcal)/UCFW for ΔH, and −4.09 J (−0.98 cal)/UCFW deg for ΔS. All these values are sufficiently close to zero that they may be considered to be so. The question is raised as to the quantity of ATP energy conserved within the substance of the protein as it is synthesized from succinic acid. It is calculated that only 3.8% of the total free energy available from ATP that is required during protein anabolism can have been conserved within the substance of the protein, there being a net conversion of the remaninder into heat and entropy.
Automatic containment sampling of recombinant escherichia coli fermentations
Authors: Strudsholm Kim , Emborg Claus , Sigsgaard Poul 
Published: December 2004

AbstractA containment sampling system for shake flasks and fermentors has been developed from a blood collection system used in hospitals. The core of the system is a collection vial with a vacuum inside. When a needle connected to the fermentation fluid penetrates a rubber seal on the vial, a sample is withdrawn. The system has been developed in two versions, a manual method for shake flasks, and an automated version for fermentors including cool storage of samples. The sampling system offers the same safety for fermentation containment as the original system offers safety for patients and hospital staff. © 1992 John Wiley & Sons, Inc.
A theoretical analysis of cellulase product inhibition: Effect of cellulase binding constant, enzyme/substrate ratio, and β‐glucosidase activity on the inhibition pattern
Authors: Gusakov Alexander V. , Sinitsyn Arkady P. 
Published: December 2004

AbstractTheoretical analysis of cellulase product inhibition (by cellobiose and glucose) has been performed in terms of the mathematical model for enzymatic cellulose hydrolysis. The analysis showed that even in those cases when consideration of multienzyme cellulase system as one enzyme (cellulase) or two enzymes (cellulase and β‐glucosidase) is valid, double‐reciprocal plots, usually used in a product inhibition study, may be nonlinear, and different inhibition patterns (noncompetitive, competitive, or mixed type) may be observed. Inhibition pattern depends on the cellulase binding constant, enzyme concentration, maximum adsorption of the enzyme (cellulose surface area accessible to the enzyme), the range in which substrate concentration is varied, and β‐glucosidase activity. A limitation of cellulase adsorption by cellulose surface area that may occur at high enzyme/substrate ratio is the main reason for nonlinearity of double‐reciprocal plots. Also, the results of calculations showed that material balance by substrate, which is usually neglected by researchers studying cellulase product inhibition, must be taken into account in kinetic analysis even in those cases when the enzyme concentration is rather low. © 1992 John Wiley & Sons, Inc.
Functional differentiation and primary metabolism of mouse mammary epithelial cells in extended‐batch and hollow‐fiber culture
Authors: Sharfstein Susan T. , Gaillard Béatrice , Blanch Harvey W. , Clark Douglas S. 
Published: December 2004

AbstractGrowth, expression of functional differentiation (as characterized by synthesis and secretion of milk proteins), and primary metabolism were studied for a mouse mammary epithelial cell line, COMMA‐1D, in extended‐batch and hollow‐fiber reactor cultures. Batch cultures were performed on Costar polycarbonate membrane inserts, allowing basal and apical exposure to medium. Protein production was induced in both batch and hollow‐fiber cultures in hormonesupplemented medium. In batch cultures, high levels of protein production and secretion were maintained for 18 days. Once differentiation was induced, the rate of deinduction was low, even in medium containing epidermal growth factor (EGF) and serum; cells continued to express and secrete proteins for at least 12 days after prolactin and hydrocortisone were removed. Cells in both batch and hollow‐fiber cultures were highly glycolytic and exhibited low rates of glutaminolysis. In batch culture on membrane inserts, cells showed polarized metabolism between the apical and basal side, maintaining significant gradients of glucose and lactate. Medium hormonal composition and subsequent differentiation affected both glucose uptake and lactate yield for COMMA‐1D in batch culture. © 1992 John Wiley & Sons, Inc.
Determination of intraparticle immobilized enzyme distribution under moderate diffusion conditions
Authors: Hossain Md. M. , Do D. D. 
Published: December 2004

AbstractThe method Presented earlier by Hossain and Do determine the active enzyme distribution and relevant rate parameters under the condition of strong diffusional resistance is extended in this article to cover the cases of comparable diffusion and reaction rates (3 < ϕ < 20). The theory proposed herein is tested wtih the experimental data of hydrogen perioxide‐catalase immobilized on controlled‐pore glass (CPG) particles of small size (150 μm). © 1992 John Wiley & Sons, Inc.
Application of computer to monitoring and control of fermentation process: Microbial conversion of ML‐236B Na to pravastatin
Authors: Hosobuchi Masahiko , Kurosawa Kazuyuki , Yoshikawa Hiroji 
Published: December 2004

AbstractAn automatic feeding process for microbial hydroxylation of ML236B sodium salt (ML‐236B Na; compactin) by Streptomyces carbophilus SANK 62585 was developed. The hydroxylated product, pravastatin sodium salt (pravastatin; trade name Mevalotin), is an inhibitor of 3‐hydroxy‐3‐methyglutaryl–coenzyme A reductase (HMG–CoA reductase) used as cholesterol‐lowering drug. The hydroxylation activity of S. carbophilus was induced by the addition of ML236B Na to culture broth but inhibited by high concentration of ML236B Na. In order to obtain high conversion yield, it was necessary to maintain optimum ML236B Na concentration throughout the fermentation by continuous feeding. For this purpose, we developed an on‐line monitoring method, which mainly consisted of a cross‐flow filtration module, high‐performance liquid chromatography (HPLC) analyzer, feed pump, and microcomputer for regulation of ML236B Na concentration. An algorithm for control of ML236B Na feed rate based on feedback and feed‐forward control where conversion rate after Δt was estimated by using regression analysis of the five latest values of conversion rate. In a fed‐batch culture employing this system, the concentration of ML236B Na was maintained at optimum level during the fermentation and the productivity of pravastatin was increased threefold over that obtained in manual control culture. © 1993 John Wiley & Sons, Inc.
Lipase immobilized on hydrophobic porous polymer supports prepared by concentrated emulsion polymerization and their activity in the hydrolysis of triacylglycerides
Authors: Ruckenstein E. , Wang X. 
Published: December 2004

AbstractMicroporous polymer supports for the immobilization of lipase have been prepared by the polymerization of a concentrated emulsion precursor. The concentrated emulsion consists of a mixture of styrene and divinyl‐benzene containing a suitable surfactant and an initiator as the continuous phase and water as the dispersed phase. The volume fraction of the latter phase was greater than 0.74, which is the volume fraction of the dispersed phase for the most compact arrangement of spheres of equal radius. The lipase from Candida rugosa has been immobilized on the internal surface of the hydrophobic microporous poly(styrene‐divinyl benzene) supports and used as biocatalysts for the hydrolysis of triacylglycerides. The effects of the amount of surfactant, of the molar ratio of divinylbenzene/styrene in the continuous phase, and of the aquaphilicity of the supports on the adsorption, activity, and stability of the immobilized lipase have been investigated. The microporous poly(styrene‐divinylbenzene) adsorbents constitute excellent supports for lipase because both the amount adsorbed is large and the rate of enzymatic reaction per molecule of lipase is higher for the immobilized enzyme than for the free one. © 1993 John Wiley & Sons, Inc.
Application of continuous zone electrophoresis to preparative separation of proteins
Authors: Nath Sunil , Schütte Horst , Hustedt Helmut , Deckwer Wolf‐Dieter 
Published: December 2004

AbstractA comprehensive study of the application of continuous zone electrophoresis to preparative separation of proteins in free solution is presented. First, the influence of electric field strength, buffer residence time in the chamber, sample flow rate, and sample concentration on separation resolution and throughput were studied. Using multiple injections of sample into the electrophoresis chamber, a throughput of 500 mg protein/h was achieved for partially purified model proteins. Experiments on Escherichia coli crude extracts yielded a fivefold purification of β‐galactosidase along with a simultaneous separation of proteins from cell debris in a single step. Experiments correlating the electrophoretic mobility in continuous electrophoresis with the elution behavior in ion‐exchange chromatography were performed on more than a dozen proteins which conclusively showed that separation of proteins in continuous zone electrophoresis is governed by net surface charge. Based on these results, the fraction numbers in which the proteins eluted could be correctly predicted. Proteins and enzymes with differences >0.5 M elution molarities in ion‐exchange chromatography were separated by continuous zone electrophoresis on a preparative scale (mg/h or g/h) with >90% recovery. This corresponds to a preparative scale separation of proteins and enzymes which differ in apparent electrophoretic mobility by only 0.70 × 10−5 cm2/V · s. © 1993 John Wiley & Sons, Inc.
TCE degradation in a methanotrophic attached‐film bioreactor
Authors: Fennell Donna E. , Nelson Yarrow M. , Underhill Sheila E. , White Thomas E. , Jewell William J. 
Published: December 2004

AbstractTrichloroethene was degraded in expanded‐bed bioreactors operated with mixed‐culture methanotrophic attached films. Biomass concentrations of 8 to 75 g volatile solids (VS) per liter static bed (Lsb) were observed. Batch TCE degradation rates at 35°C followed the Michaelis–Menten model, and a maximum TCE degradation rate (qmax) of 10.6 mg TCE/gVS · day and a half velocity coefficient (KS) of 2.8 mg TCE/L were predicted. Continuous‐flow kinetics also followed the Michaelis–Menten model, but other parameters may be limiting, such as dissolved copper and dissolved methane—qmax and KS were 2.9 mg TCE/gVS · day and 1.5 mg TCE/L, respectively, at low copper concentrations (0.003 to 0.006 mg Cu/L). The maximum rates decreased substantially with small increases in dissolved copper. Methane consumption during continuous‐flow operation varied from 23 to 1200 g CH4/g TCE degraded. Increasing the influent dissolved methane concentration from 0.01 mg/L to 5.4 mg/L reduced the TCE degradation rate by nearly an order of magnitude at 21°C. Exposure of biofilms to 1.4 mg/L tetrachloroethene (PCE) at 35°C resulted in the loss of methane utilization ability. Tests with methanotrophs grown on granular activated carbon indicated that lower effluent TCE concentrations could be obtained. The low efficiencies of TCE removal and low degradation rates obtained at 35°C suggest that additional improvements will be necessary to make methanotrophic TCE treatment attractive. © 1993 John Wiley & Sons, Inc.
Bioenergetics and end‐product regulation of Clostridium thermosaccharolyticum in response to nutrient limitation
Authors: Hill Paul W. , Klapatch Taryn R. , Lynd Lee R. 
Published: December 2004

AbstractFermentation of xylose by Clostridium thermosaccharolyticum was studied in batch and continuous culture in which the limiting nutrient was either xylose, phosphate, or ammonia. Transient results obtained in continuous cultures with batch grown inoculum and progressively higher feed substrate concentrations exhibited ethanol selectivities (moles ethanol/moles other products) in excess of 11. The hypothesis that this high ethanol selectivity was a general response to mineral nutrient limitation was tested but could not be supported. Growth and substrate consumption were related by the equation qs(1 − Y)GATP = (μ/Y) + m, with qs the specific rate of xylose consumption (moles xylose/hour · g cells), Y the carbon based cell yield (g cell carbon/g substrate carbon), GATP the ATP gain (moles ATP produces/mol substrate catabolized), μ the specific growth rate (1/h), Y the ATP‐based cell yield (g cells/mol ATP), and m the maintenance coefficient (moles ATP/hour · g cells). Y was found to be 11.6 g cells/mol ATP, and m 9.3 mol ATP/hour · g cells for growth on defined medium. Different responses to nutrient limitation were observed depending on the mode of cultivation. Batch and immobilized cell continuous cultures decreased GATP by initiating production of the secondary metabolites, propanediol, and in some cases, D‐lactate; in addition, batch cultures increased the fractional allocation of ATP to maintenance and/or wastage. Nitrogen‐limited continuous free‐cell cultures maintained a constant cell yield, whereas phosphate‐limited continuous free‐cell cultures did not. In the case of phosphate limitation, the decreased ATP demand associated with the lowered cell yield was accompanied by an increased rate of ATP consumption for maintenance and/or wastage. Neither nitrogen or phosphorus‐limited continuous free‐cell cultures exhibited an altered GATP in response to mineral nutrient limitation, and neither produced secondary metabolites. © 1993 John Wiley & Sons, Inc.
Perfusion strategy for rosmarinic acid production by Anchusa officinalis
Authors: Su Wei Wen , Lei Fei , Su Ling Yuan 
Published: December 2004

AbstractThe production of an intracellular secondary metabolite rosmarinic acid (RA) by plant cell suspensions of Anchusa officinalis cultivated with intermittent medium exchange is investigated. Initially, a two‐stage perfusion culture method was employed. After being cultured in the batch mode for ca. 6 days in B5 medium plus 3% sucrose, 1 mg/L 2,4‐dichlorophenoxyacetic acid (2,4‐D), and 0.1 mg/L kinetin (2,4‐D B5 medium), Anchusa culture was cultivated to high cell density by perfusion during the growth stage using a hormone‐free Gamborg B5 medium supplemented with 6% sucrose. This was followed by a production stage, in which a complete medium exchange into B5 medium plus 3% sucrose and 0.25 mg/L naphthleneacetic acid (NAA) was conducted. The two‐stage perfusion culture had a higher maximum culture RA concentration but a lower RA content per cell than the batch stock culture maintained in the 2,4‐D B5 medium. Higher culture RA concentration was due primarily to high cell density. The high packed cell volume, however, seemed to reduce the synergistic effect of NAA on RA synthesis. Subsequently, a single‐stage perfusion culture method was investigated. The best result was obtained by growing the culture in the batch mode for ca. 10 days using B5 medium supplemented with 3% sucrose and 0.25 mg/L NAA, followed by perfusing the culture with B5 medium plus 6% sucrose and 0.25 mg/L NAA at a constant perfusion rate of 0.1/day. A maximum cell dry weight of 35 g/L and a RA concentration of almost 4 g/L were achieved. This is the highest RA concentration ever reported in the Anchusa culture. © 1993 John Wiley & Sons, Inc.
A two‐plane tubular photobioreactor for outdoor culture of Spirulina
Authors: Torzillo Giuseppe , Carlozzi Pietro , Pushparaj Benjamin , Montaini Elena , Materassi Riccardo 
Published: December 2004

AbstractA photobioreactor in the form of a 245‐m‐long loop made of plexiglass tubes having an inner diameter of 2.6 cm was designed and constructed for outdoor culture of Spirulina. The loop was arranged in two planes, with 15 8‐m‐long tubes in each plane. In the upper plane, the tubes were placed in the vacant space between the ones of the lower plane. The culture recycle was performed either with two airlifts, one per plane, or with two peristaltic pumps. The power required for water recycle in the tubular photobioreactor, with a Reynolds number of 4000, was 3.93 × 10−2 W m−2. The photobioreactor contained 145 L of culture and covered an overall area of 7.8 m2. The photobioreactor operation was computer controlled. Viscosity measurements performed on Spirulina cultures having different biomass concentrations showed non‐Newtonian behavior displaying decreasing viscosity with an increasing shear rate. The performance of the two‐plane photobioreactor was tested under the climatic conditions of central Italy (latitude 43.8° N, longitude 11.3° E). A biomass concentration of 3.5 g L−1 was found to be adequate for outdoor culture of Spirulina. With a biomass concentration of 6.3 g L−1, the biomass output rate significantly decreased. The net biomass output rate reached a mean value of 27.8 g m−2 d−1 in July; this corresponded to a net photosynthetic efficiency of 6.6% (based on visible irradiance). © 1993 John Wiley & Sons, Inc.