bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of photon correlation spectroscopy as a technique for detecting culture contamination
Authors: Jepras R. I. , Perkins E. A. , Rarity J. , Carr R. J. G. , Clarke D. J. , Atkinson T. 
Published: December 2004

AbstractThe application of photon correlation spectroscopy (PCS) to detect culture contamination in chemostats was studied. It was found that the presence of a given particle size in a population of particles of a different size could be detected, but this ability was strongly dependent on particles of a different size could be detected, but this ability was strongly dependent on particle size difference and was most sensitive when contaminants are larger than the host. The inherent polydisparity of actively growing and dividing microbial cells negates any advantage in the use of multi‐angle PCS to detect contaminants.
Utility of culture redox potential for identifying metabolic state changes in Amino acid fermentation
Authors: Kwong Simon C. W. , Rao Govind 
Published: December 2004

AbstractWe investigated the relationship of dissolved oxygen and culture redox potential (CRP) on amino acid production. Corynebacterium glutamicum ATCC 14296 was used for all experiments. The fermentation can be divided into a growth phase and a production phase. Our results indicate that in order to get higher amino acid production, a lower oxygen supply during the exponential phase is favored. A higher oxygen supply rate appears to be necessary during the production phase. Culture redox potential (CRP) was used to monitor the fermentation. CRP readings were observed to drop to a characteristic minimum value as the metabolic state changed from a growth to production phase. This was evidenced by the commencement of amino acid production and a simultaneous uptake of lactate. Upon lactate exhaustion, the CRP increased abruptly. At the same time, maximal amino acid yields were observed. By the use of minimum CRP as an indication of metabolic phase changes, the agitation rate was changed to increase oxygen supply during the production phase. This significantly increased amino acid production. These results show that culture redox potential measurements can be used to monitor and optimize amino acid production by process manipulation.
Recovery of L‐lysine from dilute water solutions by liquid pertraction
Authors: Boyadzhiev L. , Atanassova I. 
Published: December 2004

AbstractKinetics of liquid membrane (Pertraction) recovery of L‐lysine from dilute aqueous solutions is studied in a tow‐compartment glass cell. A 5% (vol) solution of the cation exchange carrier di(2‐ethylhexyl)phosphoric acid in n‐decane was used as intermediate, membrane liquid. The third stripping phase was 1/v hydrochloric acid. The reaction mechanism and stoichiometry were defined, and on the basis of the proposed mathematical model of the process and the experimental data obtained, the mass transfer coefficients were evaluated. It was found that overall transfer rate is controlled by the eddy diffusion of transported species in the donor and membrane liquids. The results proved the feasibility of the pertraction process for recovery and concentration of L‐lysine from its dilute aqueous solutions.
Large‐Scale, High‐density freezing of hybridomas and its application to high‐density culture
Authors: Ninomiya Nobutaka , Shirahata Sanetaka , Murakami Hiroki , Sugahara Takuya 
Published: December 2004

AbstractLarge‐scale, high‐density freezing of hybridomas was studied to apply frozen cells to start high‐density culture. We showed here that hybridomas can be frozen at 1.5 × 108 cells/mL, without decrement in viability and proliferating activity. Blood transporting bags were used for large‐scale freezing to store 25 mL of cell suspension with a cell density, 1.5 × 108/mL. The number of cells stored in a bag (3.0 × 109 cells) was enough to start a high‐density culture at a 10 times higher cell density (6.0 × 106 cells/mL) than normal inoculation, and the cells proliferated to 107 cells/mL within 2 days. These results indicate that the large‐scale freezing method is useful for large‐scale culture of mammalian cells.
Effect of immiscible organic solvents on activity/stability of native chymotrypsin and immobilized‐stabilized derivatives
Authors: Blanco Rosa M. , Halling Peter J. , Bastida Agatha , Cuesta Carmen , Guisáun Jose M. 
Published: December 2004

AbstractWe have developed different activity/stability tests to evaluate the possibilities of fully dispersed chymotrypsin derivatives as industrial catalysts in biphasic systems. We have tested different immiscible organic solvents (log P ranged from 0.65 to 2.8) and used different enzyme derivatives (soluble chymotrypsin and one‐point and multipoint covalent attached derivatives). Special emphasis has been given to the role of the “exact composition of the aqueous phase.”High phosphate concentrations largely protect every hymotrypsin derivative from the distorting effects of dissolved solvent molecules. The effects on the activity and stability of soluble chymotrypsin due to saturating solvent concentrations in an aqueous solution, and the much more severe effects of contact with the phase interface in a stirred biphasic system, all show the opposite trend for the influence of solvent polarity to that generally observed for biocatalysts. For example, deleterious effects decline in the order chloroform, dichloromethane, ethyl acetate. On the contrary, with or without stirring, our stabilized chymotrypsin‐agarose derivatives are much more stable against these water‐immiscible solvents, and their relative effects follow the normal trend. From these integrated activity and stability tests we can conclude that fully dispersed immobilized‐stabilized derivatives seem to be an interesting alternative to develop industrial biphasic processes catalyzed by chymotrypsin.
Enzyme‐Catalyzed oxidation of cholesterol in physically characterized water‐in‐oil microemulsions
Authors: Hedström Gun , Slotte J. Peter , Molander Ove , Rosenholm Jarl B. 
Published: December 2004

AbstractThe enzymatic conversion of cholesterol to cholestenone by cholesterol oxidase (Brevibacterium sp.)in reversed micelles in a system composed of AOT/isooctane/water/cholesterol has been examined. The catalytic activity of the enzyme was correlated with the physicochemical properties of water in water‐in‐oil (w/o) microemulsion systems. In a system consisting of 3 wt % AOT in isooctane, reversed micelles started to form as the [H2O]/[AOT] (e.g., the w0) ratio increased above 4–5. The formation of reversed micelles with a core of neat (bulk) water was verified from determinations of both the partial molar volume of water and the scissors vibration of water [with Fourier transform infrared (FTIR) spectroscopy] in the w/o microemulsion systems. A plot of enzyme activity vs. w0 indicated that the hydration of enzyme molecules per se was not sufficient to give rise to catalytic activity. Instead, it appeared that the formation of an aqueous micellar core was necessary for full activation of the enzyme. Based on micelle size distribution analysis, it was estimated that about one micelle per one thousand contained an enzyme molecule. Since the apparent reaction rate could be markedly enhanced by increasing the enzyme/water ratio, we conclude that the number of enzyme‐containing micelles was an important rate‐limiting factor in the system.
Molecular weight distribution of chitosan isolated from Mucor rouxii under different culture and processing conditions
Authors: Arcidiacono S. , Kaplan D. L. 
Published: December 2004

AbstractThe isolation of chitosan from a fungal source offers the potential of a product with controlled physicochemical properties not obtainable by the commercial chemical conversion of crustacean chitin. A variety of culture and processing protocols using Mucor rouxii were studied for their effects on biomass yield and chitosan molecular weight. Weight‐averaged molecular weight determined by gel permeation chromotography ranged from 2.0 × 105 to approximately 1.4 × 106 daltons. The chitosan yield ranged from 5% to 10% of total biomass dry weight and from 30% to 40% of the cell wall. Of the culture parameters studied, length of incubation and medium composition effected biomass production and molecular weight. Modification of the processing protocol, including the type and strength of acid, and cell wall disruption in acid prior to refluxing were used to optimize the efficiency of chitosan extraction.The degree of deacetylation of fungal and commercial chitosans was compared using infrared spectrometry, titration, and first derivative of UV absorbance spectrometry. The chitosan obtained directly from the fungal cell wall had a higher degree of deacetylation than commercial chitosan from the chemical conversion process.
Development of the optimal inoculation conditions for microcarrier cultures
Authors: Forestell Sean P. , Kalogerakis Nicolas , Behie L. A. , Gerson Donald F. 
Published: December 2004

AbstractThe environmental conditions under which anchorage‐dependent mammalian cells are grown are not necessarily those under which a culture should be initiated. Cell attachment is a physical process, and those factors which affect forces involved in cell attachment differ from the biological factors which affect cell growth. We have conducted an extensive experimental study to define clearly the optimal environmental conditions for MRC‐5 cell attachment onto microcarriers. These inoculation conditions are particularly important when the serial propagation of mammalian cells on microcarriers is considered as in a human vaccine production process. The conditions which were investigated are: initial serum content (% v/v), initial pH, inoculation level (cells/bead), agitation rate (rpm), and the concentration of microcarriers (g/L). The initial distribution of attached cells was found to have a significant affect on the overall efficiency of anchorage‐dependent cell cultures, and was used to evaluate attachment efficiency. Based on the experimental results, we propose an optimized protocol for the inoculation of microcarrier cultures.
Population balance between producing and nonproducing hybridoma clones is very sensitive to serum level, state of inoculum, and medium composition
Authors: Chuck Alice S. , Palsson Bernhard O. 
Published: December 2004

AbstractSecreting and nonsecreting hybridoma populations derived from the murine hybridoma cell line 167.4G5.3 were each grown in batch culture in low serum and serum‐free media. Under serum‐free conditions, a secreting population gained on a predominantly nonsecreting population and competed with the existing antibody‐deficient cells effectively. It was found that this competition was sensitive to state of inoculum and medium composition. We conclude that the competition between a secreting and nonsecreting, or more generally, a producing and nonproducing, population is important; the appearance of the latter may not be a significant setback in terms of expected product titer.
Monoclonal antibody production in dialyzed continuous suspension culture
Authors: Linardos Theodor I. , Kalogerakis Nicolas , Behie Leo A. , Lamontagne Louis R. 
Published: December 2004

AbstractHybridoma cell growth and monoclonal antibody production in dialyzed continuous suspension culture were investigated using a 1.5‐L Celligen bioreactor. Medium supplemented with 1.5% fetal bovine serum was fed directly into the reactor at a dilution rate of 0.45 d−1. Dailysis tubing with a molecular weight cut‐off (MWCO) of 1000 was coiled inside the bioreactor. Fresh medium containing no serum or serum substitues passed through the dialysis tubing at flow rates of 2 to 5 L/d. The objective was to remove low molecular weight inhibitors, such as lactic acid and ammonia, by diffusion through the tubing, while continuoulsy replenishing essential nutrients by the same mechanism. Due to the low MWCO of the dialysis tubing high molecular weight components such as growth factors and antibody were not removed by the dialyzing stream. In the batch start‐up phase, the monoclonal antibody (MAb) titer was almost 3 times that achieved in typical batch cultures (i.e., 170 to 180 mg/L). During dialyzed continuous operation, a substantial increase (up to 40%) in cell density, monoclonal antibody (MAb) titer, and reactor MAb productivity was observed, as compared with a conventional continuous suspension culture. The cell viability and the specific MAb productivity remained practically constant at different dialysis rates. This finding suggests that the steady state growth and death rate in continuous suspension hybridoma cultures are not direct functions of the nutrient or inhibitor concentrations.
Development of a helical‐ribbon impeller bioreactor for high‐density plant cell suspension culture
Authors: Jolicoeur M. , Chavarie C. , Carreau P. J. , Archambault J. 
Published: December 2004

AbstractA double helical‐ribbon impeller (HRI) bioreactor with a 11‐L working volume was developed to grow high‐density Catharanthus roseus cell suspensions. The rheological behavior of this suspension was found to be shear‐thinning for concentrations higher than 12 to 15 g DW · L−1. A granulated agar suspension of similar rheological properties was used as a model fluid for these suspensions. Mixing studies revealed that surface baffling and bottom profiling of the bioreactor and impeller speeds of 60 to 150 rpm ensured uniform mixing of suspensions. The HRI power requirement was found to increase singnificantly for agar suspensions higher than 13 g DW · L−1, in conjunction with the effective viscosity increase. Oxygen transfer studies showed high apparent surface oxygen transfer coefficients (kLa ∼4 to 45 h−1) from agar suspensions of 30 g DW · L−1 to water and for mixing speeds ranging from 120 to 150 rpm. These high surface kIa values were ascribed to the flow pattern of this bioreactor configuration combined with surface bubble generation and entrainment in the liquid phase caused by the presence of the surface baffles. High‐density C. roseus cell suspension cultures were successfully grown in this bioreactor without gas sparging. Up to 70% oxygen enrichment of the head space was required to ensure sufficient oxygen supply to the cultures so that dissolved oxygen concentration would remain above the critical level (≥10% air saturation). The best mixing speed was 120 rpm. These cultures grew at the same rate (∼0.4 d−1) and attained the same high biomass concentrations (∼25 to 27 g DW · L−1, 450 to 500 g filtered wet biomass · L−1, and 92% to 100% settled wet biomass volume) as shake flask cultures. The scale‐up potential of this bioreactor configuration is discussed.
Metabolic characterization of a L‐lysine‐producing strain by continuous culture
Authors: Kiss Robert D. , Stephanopoulos Gregory 
Published: December 2004

AbstractContinuous culture experiments with the L‐producer, Corynebacterium glutamicum, were carried out to characterize the effect of specific growth rate on fermentation yields, specific rates, productivities, and fluxes through the primary metabolism. The specific productivity of L‐lysine exhibited a maximum with respect to specific growth rate, with an initial growth‐associated behavior up to specific growth rates of about 0.1 h−1, and a constant specific productivity for specific growth rates in the range of about 0.1 to 0.2 h−1. The productivity dropped at specific growth rates larger than about 0.2 h−1. The yield of L−lysine on glucose increased approximately linearly with decreasing specific growth rate over the entire range studied, as did the respiratory quotient. A direct relationship was established between the culture respiratory quotient and the L‐lysine yield. By explicitly accounting for glucose used for biomass synthesis, it was shown that the strain synthesizes L‐lysine with an intrinsic yield, or efficiency, of about 0.41 mol L‐lysine/mol glucose, compared with the theoretical yield of 0.75 mol/mol. Metabolic flux modeling based on the continuous culture data suggests that the production of ATP is not likely to be a limiting factor in L‐lysine production, and that a high TCA cycle activity, coupled with a tightly controlled split of metabolite flow at the PEP node, is likely the cause of the large discrepancy between theoretical and actual yields in L‐lysine fermentations.
Acetic acid formation in escherichia coli fermentation
Authors: Han Keehyun , Lim Henry C. , Hong Juan 
Published: December 2004

AbstractAcetic acid formation in Escherichia coli fermentation has been studied in continuous cultures. Experimental results suggest that the limited capacity of the oxidative metabolism (perhaps the limited capacity of TCA cycle) may be responsible for acetic acid formation. At low growth rates, both anabolic and catabolic requirements may be satisfied by the oxidative metabolism. However, at high growth rates these two demands may exceed the capacity of the oxidative metabolism alone. It is proposed that under these circumstances, E. coli reorganizes the oxidative metabolism to first meet the anabolic requisition and then supply the necessary amount of energy using both the remaining capacity of the oxidative metabolism and acetic acid formation metabolism. Escherichia coli selects acetic acid synthesis as the aerobic energy source because it generates the second largest amount of ATP and NADH2. According to our proposition, acetic acid formation could be reduced by decreasing the anabolic requirement, i.e., reducing glucose uptake, or by increasing the capacity of the oxidative metabolism. These two approaches were experimentally confirmed by observing reduced acetic acid formation by reducing the glucose uptake with a yeast extract addition and enhancing the capacity of oxidative metabolism with a methionine addition.
Growth of the obligate methylotroph Methylobacillus flagellatum under stationary and nonstationary conditions during continuous cultivation
Authors: Baev M. V. , Schklyar N. L. , Chistoserdova L. V. , Chistoserdov A. Y. , Polanuer B. M. , Tsygankov Y. D. , Sterkin V. E. 
Published: December 2004

AbstractThe growth characteristics of a chemostat culture of the obligate methylotrophic bacterium Methylobacillus flagellatum have been determined. Steady‐state cultures growing at a rate of 0.73–0.74 h−1, equal to the maximal growth rate, were obtained under oxyturbidostat cultivation conditions. The response of a chemostat culture to a pulse increase of methanol concentration was studied. It was shown that slow and rapidly growing cultures of M. flagellatum responded differently to pulse methanol addition. The growth characteristics of slow‐growing cultures decreased after methanol addition compared to those of stationary chemostat cultures. The growth characteristics of rapidly growing cultures were practically unchanged with and without pulse methanol addition.
In search of a thermodynamic description of biomass yields for the chemotrophic growth of microorganisms
Authors: Heijnen J. J. , Van Dijken J. P. 
Published: December 2004

AbstractCorrelations for the prediction of biomass yields are valuable, and many proposals based on a number of parameters (YATP, YAve, ηo, Yc, Gibbs energy efficiencies, and enthalpy efficiencies) have been published. This article critically examines the properties of the proposed parameters with respect to the general applicability to chemotrophic growth systems, a clear relation to the Second Law of Thermodynamics, the absence of intrinsic problems, and a requirement of only black box information. It appears that none of the proposed parameters satisfies all these requirements. Particularly, the various energetic efficiency parameters suffer from major intrinsic problems. However, this article will show that the Gibbs energy dissipation per amount of produced biomass (kJ/C‐mod) is a parameter which satisfies the requirements without having intrinsic problems. A simple correlation is found which provides the Gibbs energy dissipation/C‐mol biomass as a function of the nature of the C‐source (expressed as the carbon chain length and the degree of reduction). This dissipation appears to be nearly independent of the nature of the electron acceptor (e.g., O2, No3−, fermentation). Hence, a single correlation can describe a very wide range of microbial growth systems. In this respect, Gibbs energy dissipation is much more useful than heat production/C‐mol biomass, which is strongly dependent on the electron acceptor used. Evidence is presented that even a net heat‐uptake can occur in certain growth systems.The correlation of Gibbs energy dissipation thus obtained shows that dissipation/C‐mol biomass increases for C‐sources with smaller chain length (C6 → C1), and increases for both higher and lower degrees of reduction than 4. It appears that the dissipation/C‐mol biomass can be regarded as a simple thermodynamic measure of the amount of biochemical “work” required to convert the carbon source into biomass by the proper irreversible carbon‐carbon coupling and oxidation/reduction reactions. This is supported by the good correlation between the theoretical ATP requirement for biomass formation on different C‐sources and the dissipation values (kJ/C‐mol biomass) found. The established correlation for the Gibbs energy dissipation allows the prediction of the chemotrophic biomass yield on substrate with an error of 13% in the yield range 0.01 to 0.80 C‐mol biomass/(C)‐mol substrate for aerobic/anaerobic/denitrifying growth systems.
Prediction of a protein band profile in preparative reversed‐phase gradient elution chromatography
Authors: Zoubaïr M. , Fallah El , Guiochon Georges 
Published: December 2004

AbstractThe overloaded band profiles of lysozyme in reversedphase preparative chromatography were recorded on a C18 chemically bonded silica column, with acetonitrile/water as the mobile phase. These experiments were carried out under isocratic conditions at 31.6, 31.9, and 32.2% acetonitrile (ACN) for loading factors up to 43% of the column saturation capacity and under linear‐solvent‐strength gradientelution with gradient slopes of 0.5 and 1% ACN/min, for loading factors up to 11.3%. The adsorption isotherms of lysozyme were measured for the same solvent compositions and found to be accurately accounted for by a bi‐Langmuir isotherm model.With the use of a Craig model implementation of the equilibrium‐dispersive model of chromatography, the band profiles of lysozyme were calculated. An excellent agreement was observed between these calculated profiles and the experimental profiles recorded at loading factors below 5%. By contrast, band profiles calculated using a Langmuir isotherm failed to describe the experimental bands. At column loadings exceeding 8%, a slight but systematic deviation takes place between calculated and experimental profiles. It is most probably explained by the considerable concentration effect of the gradient, making the band experience phase equilibrium in a concentration range that exceeds largely the one where the isotherm data have been measured.
Effect of organic solvents on enzymatic production of cyclodextrins from unliquefied corn starch in an attrition bioreactor
Authors: Lee Yun‐Dong , Kim Hak‐Sung 
Published: December 2004

AbstractCyclodextrins were produced from unliquefied corn starch in the presence of water‐miscible organic solvents using cyclodextrin glycosyltransferase (CGTase) in an attrition bioreactor. The production yield was singnificatly increased by isopropanol and tertiary butanol, and maximum enhancement was observed to be about 40% by 5% tertiary butnol. Increase in the production of cyclodextrins by organic solvents seems to be due to the fact that organic solvents decreased the product inhibition of CGTase by forming an inclusion complex with cyclodextrins.