bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dual substrate removal by an axenic bacterial culture
Authors: Machado Ranjit J. , Grady C. P. Leslie 
Published: December 2004

AbstractA pure bacterial culture capable of utilizing either L‐lysine or 2‐chlorophenol (2‐CP) as sole carbon source was isolated and used in continuous culture experiments to determine its response to dual substrate limitation by those two compounds. Dilution rate and feed composition were each set at three levels in a two factorial experimental design. The total chemical oxygen demand (COD) of the feed was fixed at 225 mg/L and its composition was varied by changing the ratio of lysine to 2‐CP. The effects of the two independent variables (dilution rate and feed composition) on the concentrations of cells, lysine, COD, and dissolved organic carbon (DOC) in the reactors were systematic whereas the effects on the 2‐CP concentration were less predictable. The concentrations of the two substrates responded to the two independent variables in a complex interactive manner which is not explained by existing models for dual, substitutable substrates. Rather, the results suggested that the prediction of the fate of a single organic component in a reactor receiving a multicomponent feed is a very difficult task.
Experimental investigation of G6P production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow‐fiber reactor
Authors: Ishikawa Haruo , Takase Susumu , Tanaka Takenori , Hikita Haruo 
Published: December 2004

AbstractEnzymatic synthesis of glucose 6‐phosphate from glucose and ATP catalyzed by glucokinase from B. stearothermophilus and enzymatic regeneration of ATP from ADP and acetyl phosphate catalyzed by acetatekinase from B. stearothermophilus were simultaneously performed in an Ultrafiltration hollow‐fiber reactor of the multitubular heat‐exchanger type. Experimental results of space–time yield, the conversion, and ATP recycle number were in good agreement with the theoretical predictions based on the simple analytical model developed in the preceding article. The best results for space–time yield and conversion were Ys = 1.97 mol/m3 h and X = 92.8%, respectively, under the same conditions, and the best result for the ATP recycle number was NR = 2130 under conditions different from those above. However, Ys = 1.72 mol/m3 h, X = 81.2%, and NR = 1620 were the results when the space–time yield, conversion, and recycle number were at the highest in combination under the same conditions. Results of long‐term operation showed that the apparent remaining activity of the enzyme system was ca. 55% after continuous operation for 16 days, the decrease in the enzyme activity being faster than that expected from their half‐life times determined individually in the homogeneous system.
A population balance model of enzymatic lysis of microbial cells
Authors: Hunter J. B. , Asenjo J. A. 
Published: December 2004

AbstractA model is proposed for enzymatic lysis of microbial cells based on number balances over the distribution of cell‐wall mass in a population of cells. Analytical solutions to the population balance equations were obtained by the method of characteristics for simple reaction kinetics. The model has been used to analyze the following cases of lysis in a nonhomogeneous cell population: wall hydrolysis with cell rupture and product release, the effect of a distribution of lysis rates, and lysis of two‐layer cell walls. Rate expressions for the reactions of lysis can be derived from bulk‐phase experiments; the distributions of cell size and product content can be measured independently by flow cytometric techniques. The population model also provides an explanation for the initial lag seen in lysis kinetics for virtually any initial distribution. The model demonstrates patterns of lysis and product recovery for heterogeneous populations of cells and also applies to the more general problem of soluble‐enzyme reactions with heterogeneous solid substrates.
In situ methane enrichment in anaerobic digestion
Authors: Hayes T. D. , Isaacson H. R. , Pfeffer J. T. , Liu Y. M. 
Published: December 2004

AbstractA major cost consideration in the use of anaerobic digestion to convert biomass and waste to utility‐grade gas is the expense of separating CO2 from the product gas. Anaerobic digestion has a number of inherent properties that can be exploited to increase the methane content of the gas directly produced by the digester, the most important of which is the high solubility of CO2(40‐60 times that of methane) in water under digestion conditions. The methane enrichment concept examined in this study involved the recirculation of a liquid stream from the digester through a CO2 desorption process and the return of the liquid stream back to the digester for absorption of additional CO2 produced by the conversion of organic materials. A steady‐state equilibrium model predicted that a digester gas methane content exceeding 94% could be achieved with this scheme using modest recirculation rates provided a desorption process could be designed to achieve a 60+% CO2 removal efficiency in the degassing of the liquid recycle stream. Using fixed‐film laboratory digesters operated on synthetic feedstocks, the technique of methane enrichment was tested under pressurized and unpressurized conditions. A 93 + 2% methane gas stream was produced from a volatile‐acid‐fed bench‐scale digester simulating the methanogenic stage of two‐phase digestion under conditions of (1) a pH swing achieved without caustic addition that allowed digestion at pH 7. 5 and air stripping at pH 6. 5‐7. 0, (2) digester pressurization to 30 psig, and (3) a recycle rate of 0. 33 L/L reactor/day. Significant but lower levels of methane enrichment were achieved with the single‐stage digester at the low experimental recycle rate. However, the narrow range among all experiments of CO2 desorption efficiencies achieved in air stripping the recycle stream (35‐60% CO2 removal) suggests that comparable methane enrichment‐may be achieved with unpressurized single‐stage digestion using greater recycle rates. A materials balance analysis of data from an unpressurized, single‐stage digester employing no chemical addition and using laboratory degassing efficiencies indicated that 94% methane could be produced at recycle rates of less than 1. 4 L/L reactor/day with a methane loss of less than 2%.
A model for energy‐sufficient culture growth
Authors: Tsai S. P. , Lee Y. H. 
Published: December 2004

AbstractPirt's maintenance model has been widely accepted for the effects of growth rate and maintenance on growth yield. However, the interpretation of parameters in Pirt's model as biological constants is difficult for energy‐sufficient culture growth. In this study, a mechanistic model for the growth energetics of energy‐sufficient chemostat cultures is proposed and verified with literature data. In the model, the overutilization of the energy substrate in energy‐sufficient culture growth is attributed to the defective regulation of the energy substrate metabolism and energy uncoupling. The model also uses an “energy surplus” concept to collectively represent the effects of energy excessiveness. The proposed model provides a better quantitative understanding of the maximum growth yield and maintenance of energy‐sufficient cultures. It also explains the glucose concentration effect reported in the literature.
A flow‐cytometric analysis of hybridoma growth and monoclonal antibody production
Authors: Dalili Mina , Ollis David F. 
Published: December 2004

AbstractA flow cytometric kinetic study of hybidoma growth and monoclonal antibody production is presented, along with the influence of glutamine on intracellular responses such as (relative) cell size, and cell RNA and total protein content. Specific findings are: (1) RNA content remained constant throughout the growth phase, then fell drastically as the cells entered the stationary phase. Also, in stationary phase, RNA content of antibody‐producing cells was higher than for those not secreting antibody. (2) The cell size was constant and maximal throughout exponential phase, and diminished monotonically during later stages. (3) Average protein and antibody cellular content declined dramatically upon glutamine exhaustion. Thus, relative RNA levels and cell size provided quantitative determinants of both cell growth state and antibody secretion conditions. These results encourge consideration of structured kinetic studies which recognize the quality of the biophase.
Effect of metal ion concentration on a biological reactor
Authors: Ibbotson P. G. , Spedding P. L. , Otterburn M. S. 
Published: December 2004

AbstractSaccharomyces cerevisiae (yeast) cells were employed as a source of alcohol dehydrogenase in the NAD+‐to‐NADH reaction. The cells were immobilized in calcium alginate monofilament fibers and used in a biological reactor. The alginate could not be heat sterilized since temperatures above 80 °C caused the polymer chains to degrade. The same proved true for the high pH necessary for the reaction, but the alginate strength was increased by Ba2+ solution treatment. X‐ray probe analysis showed that about 30% of the Ca2+ sites exchanged with the Ba2+ ions. The Ba2+ ions (as well as the Ca2+ ions) permeabilized the cells and increased the reaction rate. Long term trials showed that Ba2+ ions were slowly elutriated from the fiber biocatalyst, causing a drop in reaction rate. The trend certainly was reversible as far as the fiber was concerned. It is assumed that the permeabilization of the cells by the Ba2+ ions was a reversible process.
Hydrodynamic model for liquid‐impelled loop reactors
Authors: van Sonsbeek H. M. , Verdurmen R. E. M. , Verlaan P. , Tramper J. 
Published: December 2004

AbstractA new type of bioreactor, in which two liquid phases are used, is introduced and a model description of its hydrodynamic behavior is given. The model is based on the two‐phase drift‐flux model of Zuber and Findlay and on a friction coefficient derived from one‐phase flow theory. Drop sizes, necessary for model calculations, were estimated from literature correlations and photographically verified. The model predicts the continuous‐phase circulation velocity and dispersed‐phase hold‐up within an accuracy of 5% for a pilot‐plant reactor, and within 10% for a lab‐scale reactor. Only at very low ranges, especially on lab scale, is this accuracy not attained.
Factors influencing recombinant protein yields in an insect cell–bacuiovirus expression system: Multiplicity of infection and intracellular protein degradation
Authors: Licari P. , Bailey J. E. 
Published: December 2004

AbstractThe insect cell (Sf9)‐baculovirus (AcNPV) expression system was employed for the synthesis of β‐galactosidase, a model heterologous protein. In the recombinant virus studied, the lacZ gene is fused to a portion of the polyhedrin structural gene and is under the control of the polyhedrin promoter. The effect of the multiplicity of infection (MOI) on product titer was determined by infecting cells with MOI values ranging from 0 to 100 and monitoring the production of β‐galactosidase with time. The relationship between final product titer and MOI was dependent on the growth phase of the cells prior to infection. The final product titer from cells infected in the early exponential phase was relatively independent of MOI. For cells infected in late‐exponential phase there was a logarithmic relationship between the final β‐galactosidase titer and the MOI used, with the highest MOI studied resulting in greatest protein synthesis. The synthesis and degradation rates of β‐galactosidase were investigated by a pulse‐chase technique using L‐[35S]‐methionine. At 24 h postinfection, the degradation rate is of the same order of magnitude as the synthesis rate. However, the synthesis rate of β‐galactosidase increases dramatically at 96 h postinfection. During this later period, the degradation rate is negligible. Although degradation of recombinant protein occurs in this system, degradation activity declines as infection proceeds and is insignificant late in intention when recombinant protein expression is intense.
Regulation and utilization of microsin promoter turn on in a chromosomal fusion
Authors: Meehan A. J. , Minkley E. G. , Domach M. M. 
Published: December 2004

AbstractPrior work has demonstrated that the microsin antibiotics are produced by enteric bacteria when the growth medium is depleted of nutrients. Because the control loci could have biotechnical potential, and general stress‐response phenomena are of importance to understanding how bacteria survive in natural and bioreactor environments, we examined further the growth rate dependence of gene expression under the control of the microsin B17 promoter. This work entailed performing batch and chemostat growth experiments with a strain of E. coli K‐12 containing a mcbA‐lacZ gene fusion in the chromosome. Our results indicate that when a culture is presented with excess respiratory substrate, a well defined growth rate exists, below which a significant induction event occurs. However, cultures that are fermenting or highly glycolytic tend to express poorly. Additionally, the utility of the fusion strain was examined by performing fed‐batch cultivation experiments. We found that sustained production in a fed‐batch reactor can be accomplished by using a straightforward, exponential nutrient feeding profile.
A physical characterization of GAP A3 hybridoma cells: Morphology, geometry, and mechanical properties
Authors: Needham D. , Ting‐Beall H. P. , Tran‐Son‐Tay R. 
Published: December 2004

AbstractMorphological, geometrical, and rheological properties of the GAP A3 hybridoma cell line have been evaluated as a function of the cell cycle. Interference contrast video microscopy and scanning electron microscopy (SEM) showed that a sample of cells taken from the middle of the exponential growht phase displayed a range of cell morphologies, consistent with a heterogeneous growing culture. Micropipet manipulation was used to measure the geometrical (cell volume) and mechanical (cortical tension and apparent cell viscosity) properties of single cells selected at random from a sample in the middle of the exponential growth phase. Consistent with the range of morphologies, cell volumes (1400 to 5700 μm3) and apparent viscosities (430 to 1.2 × 104 P) showed a wide range of values at 37°C, demonstrating that a hybridoma cell line cannot be characterized by a single value for any one property, and that properties must be related to their cycle dependence when considering proliferating cells. Direct, video‐microscopic observation of synchronized cells, and of individual cells that were followed throughout their cell cycle, allowed us to correlated distinct morphologies with phases of the cell cycle. As the cell cycle progresses, an increase in cell volume by a factor of 3 to 4is accompanied by an overall increase in apparent cell viscosity by approximately the same ratio, consistent with an accumulation of more cytoplasmic material in the older cells. Also, a decrease in average apparent viscosity by a factor of 10. These results are important in order to evaluate the possible role of certain structural, cell‐cycle dependent features in shear and abrasion sensitivity. This is a problem of current concern in the bioreactor culture of mammalian cells.
On the calculation of the free energy change accompanying the growth of escherichia coli K‐12 on succinic acid
Authors: Battley Edwin H. 
Published: December 2004

AbstractDeterminations of the ΔG0′ accompanying the growth of Escherichia coli K‐12 on succinic acid are made using 2 different methods. The ΔG0′ accompanying catabolism could be calculated directly because the thermodynamic properties of the reactants and products are known. The ΔG′accompanying anabolism could not be calculated directly because the ΔGf value for a unit mass of cells was not known. A description is given of a deduction that the ΔG′ accompanying anabolism is zero, or nearly so. This is followed by a description of 2 methods, whereby the free energy of formation of a unit quantity of cellular substance can be calculated. The 2 values obtained by these methods are used to calculate the free‐energy change accompanying anabolism, the resultant values being 1.72 and ‐11.68 kJ, respectively, with an average of −4.98 kJ (−1.19 kcal). This value is sufficiently close to zero that it can be considered to be so, indicating that the ΔG′ accompanying metabolism is that of catabolism alone.
A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: I. Coupling between light transfer and growth kinetics
Authors: Cornet J. F. , Dussap C. G. , Dubertret G. 
Published: December 2004

AbstractThe study of the interactions between physical limitation by light and biological limitations in photobioreactors leads to very complex partial differential equations. Modeling of light transfer and kinetics and the assessment of radiant energy absorded in photoreactors require an equation including two parameters for light absorption and scattering in the culture medium. In this article, a simple model based on the simplified, monodimensional equation of Schuster for radiative transfer is discussed. This approach provides a simple way to determine a working illuminated volume in which growth occurs, therefore allowing indentification of kinetic parameters. These parameters might then be extended to the analysis of more complex geometries such as cylindrical reactors. Moreover, this model allows the behavior of batch or continuous cultures of cyanobacteria under light and mineral limitations to be predicted. © 1992 John Wiley & Sons, Inc.
Determination of antibody content in live versus dead hybridoma cells: Analysis of antibody production in osmotically stressed cultures
Authors: Reddy Sridhar , Bauer Kenneth D. , Miller William M. 
Published: December 2004

AbstractHybridomas are known to exhibit increased specific antibody production rated when subjected to environmental stress. Under these conditions, viability is low so that population‐average measurements do not properly reflect the state of viable cells. Even for flow cytometry, which gives a population distribution, special techniques must be used to discriminate between viable and nonviable cells. We describe the use of the vital stain ethidium monoazide (EMA) for independent measurement of intracellular antibody content in live and dead cells via flow cytometry. EMA is shown to be superior to light scattering techniques in identifying dead cells. We apply this technique to show that, in control batch culture, the specific antibody prodution rate and antibody content in live cells are constant during exponential growth, but decrease as cells enter the stationary phase. Antibody is retained in dead cells, but at a lower level than in live cells. We further show that, under hyperosmotic stress, the specific antibody production rate and antibody content in live both remain high during death phase. © 1992 John Wiley & Sons, Inc.
Production of the siderophore enterobactin: Use of four different fermentation systems and identification of the compound by HPLC
Authors: Seiffert Andreas , Goeke Klaus , Fielder Hans‐Peter , Zähner Hans 
Published: December 2004

AbstractThe article describes four different fermentation procedures for Escherichia coli AN311, a producer of enterobactin. A regular rotary shaker culture with a biphasic system consisting of an agar layer (as a reservoir for feeding processes) and a layer of liquid medium, 2.4 L and 10 L batch cultures, and a novel dialysis membrane fermentor were used. With the use of this latter fermentor type, the production of enterobactin could be increased by a factor of about 9.5, while growth increased by a factor of 12 compared to the other systems. For the rapid and reliable quantification of the concentration and purity of enterobactin an analytical and preparative high‐performance liquid chromatography (HPLC) method was established. The degradation compounds of this siderophore were detected by diodearray and bioassays. A comparison of total catechol production as well as the distribution between enterobactin and its degradation compounds is given. © 1993 John Wiley & Sons, Inc.
Mass transport parameters of aspen wood chip beds via stimulus‐response tracer techniques
Authors: Hradil G. , Calo J. M. , Wunderlich T. K. 
Published: December 2004

AbstractA stimulus–response tracer technique has been used to characterize packed beds of untreated, as well as acid prehydrolyzed, and enzymatically hydrolyzed aspen wood chips. Glucose was used as the tracer. Bulk liquid phase dispersion, interphase mass transfer, and intraparticle diffusion coefficients were determined for these materials as well as effective porosities and tortuosities. The untreated and prehydrolyzed aspen wood chips were found to have effective coid fractions of ca. 0.8, while the enzymatically hydrolyzed wood chips exhibited a void fraction of 0.37. Intraparticle diffusion was approximately twice as rapid in the prehydrolyzed and enzymatically hydrolyzed wood chips as in the untreated wood chips. Also, under the current experimental conditions, intraparticle diffusional transport resistance accounted for roughly half of the total tracer pulse dispersion. It is demonstrated that stimulus‐response tracer techniques can be useful and convenient probes for beds of lignocellulosic, or other conversion and/or treatment. © 1993 John Wiley & Sons, Inc.
Intrinsic fermentation kinetics of lactose in acidogenic biofilms
Authors: Yu Jian , Pinder Kenneth L. 
Published: December 2004

AbstractThe intrinsic fermentation kinetics of lactose in acidogenic biofilms were investigated in situ in a continuous flow fermentor at 35°C and pH 4.6. The external and internal mass transfer resistances to lactose molecules from bulk solution to inside the biofilms were experimentally minimized or eliminated in a thin biofilm and recycled medium. In a chemically defined culture medium, the immobilized acidogens converted lactose mainly to acetate and butyrate; the minor products included ethanol. propionate, lactate, and hydrogen. The utilization rate of lactose, as a function of lactose concentration in the fermentor, can be described by a Michaelis‐Menten equation, as can the formation rates of acetate, butyrate, and ethanol. The production rates of propionate and lactate had a liner relationship with lactose concentration under the experimental conditions. The low pH (4.6) of culture medium could depress the formation of propionate, and intermediate which is most difficulty digested by acetogenic bacteria located in the second fermentor in a two‐phase process. Production rate of acetate quickly reached a constant, and additional utilization of lactose produced more butyrate and other minor products. © 1993 John Wiley & Sons, Inc.
Comparison of three different promoter systems for secretory α‐amylase production in fed‐batch cultures of recombinant Saccharomyces cerevisiae
Authors: Park Yong Soo , Shiba Sumihisa , lijima Shinji , Kobayashi Takeshi , Hishinuma Fumio 
Published: December 2004

AbstractCloned gene expression in recombinant Saccharomyces cerevisiae 20B‐12 containing three different plasmids was compared in batch and fed‐batch cultures. The plasmids pNA3, pNA7, and pNA9 contain the α‐amylase gene under the control of SUC2, PGK, and GAL7 Promoters, respectively. The synthesis of α‐amylase was therefore induced by low glucose concentration for the SUC2 and PGK promoters, and by galactose for GAL7 promoter. The specific cell growth rates were similar among cells harboring the three different plasmids; they decreased from 0.35 to 0.38 h−1 during the cell growth phase to 0.03 to 0.06h−1 during the production phase. The secretory α‐amylase activity of cells harboring plasmid pNA7 was 129 U/mL in fed‐batch culture, which was 1.4 and 2 times as high as the activities of cells harboring plasmids pNA3 and pNA9, respectively. The secretion ratios (amount of extracellular α‐amylase activity/amounts of total α‐amylase activity) of cells harboring plasmids pNA3, pNA7, and pNA9 were 91.4%, 94.5%, and 95.3%, respectively. © 1993 Wiley & Sons, Inc.