bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physicochemical properties of the matrix proteins of three main culture vehicles
Authors: Andrews A. T. , Noble I. , Keeratatipibul S. , Asenjo J. A. 
Published: December 2004

AbstractThe protein components of three industrial recombinant expression systems: Escherichia coli, Saccharomyces cerevisiae, and a mammalian cell culture supernatant of CHO cells were characterized in terms of their molecular weight, isoelectric point, and relative surface hydrophobicity. Identification of individual proteins was done by reference to their position in protein band profiles by polyacrylamide gel electrophoresis (PAGE) of the crude material. This permitted a rapid and facile assignment of quantitative values for these three parameters to all the major protein components in these materials. Because it is the indigenous proteins in expression systems that will form the bulk of any impurities in the product, once the values of these parameters are known for any target recombinant protein, the data obtained will enable appropriate expression systems to be chosen for minimizing amounts of potential contaminants and reducing downstream processing requirements and costs. The data will also indicate which fractionation steps (i.e., charge, size or hydrophobicity‐based) are likely to be best for distinguishing between target and contaminant proteins, thus aiding and early removal of the maximum quantities of undesired protein to bring subsequent bioseparation steps down in scale and cost and up in terms of efficiency. © 1994 John Wiley & Sons, Inc.
Modeling approach to control of carbohydrate metabolism during citric acid accumulation by Aspergillus niger: I. Model definition and stability of the steady state
Authors: Torres Néstor V. 
Published: December 2004

AbstractA model of the carbohydrate metabolism and the anaplerotic synthesis of oxalacetate in Aspergillus niger, under conditions of citric and accumulation, is presented. In this first article we set the stage for subsequent analysis within the framework of the biochemical system theory (BST): we formulate the model and develop the system representation in power law forms, showing that the steady state is locally stable. In the second article, the control structure of the system is described and a rationale for the optimization of the process is developed. © 1994 John Wiley & Sons, Inc.
Interactions of microbial biofilms with toxic trace metals: 2. Prediction and verification of an integrated computer model of lead (II) distribution in the presence of microbial activity
Authors: Hsieh Ke Ming , Murgel George A. , Lion Leonard W. , Shuler Michael L. 
Published: December 2004

AbstractThe interfacial interactions of a toxic trace metal, Pb, with a surface modified by a marine film‐forming bacterium, Psedomonas atlantica, were predicted by a structured biofilm model used in conjunction with a chemical speciation model. The validity of the integrated model was tested for batch and continuous operations. Dynamic responses of the biophase due to transient lead concentration increases were also stimulated. The reasonable pre dictions achieved by the model demonstrate its utility in describing trace metal distributions in complex systems where the adsorption properties of inorganic surfaces are modified by adherent bacteria production of extracellular polymers. © 1994 John Wiley & Sons, Inc.
Optimization of microbial poly(3‐hydroxybutyrate) recover using dispersions of sodium hypochlorite solution and chloroform
Authors: Hahn Sei Kwang , Chang Yong Keun , Kim Beom Soo , Chang Ho Nam 
Published: December 2004

AbstractOptimization was carried out for the recovery of microbiol poly(3‐hydroxybutyrate) (PHB) from Alcaligenes eutrophus. This process involved the use of a dispersion made of sodium hypochlorite solution and chloroform. The dispersion enabled us to take advantage of both differential digestion by hypochlorite and solvent extraction by chloroform. The PHB recovery (%) from cell powder was maximized using a 30% hypochlorite concentration, a 90‐min treatment time, and a 1:1 (v/v) chloroform‐to‐aqueous‐phase ratio. Under these optimal conditions, the recovery was about 91% and the purity of recovered PHB was higher than 97%. The number average molecular weight, Mn of recovered PHB was about 300,000 and the weight average molecular weight Mw was about 1,020,000, compared to the original Mn of 530,000 and Mw of 1,272,000. The moderate decrease in both Mn and Mw might be ascribed to the shielding effect of chloroform. In addition, the relatively small decrease in Mw probably resulted from the loss of short PHB chains which might be water soluble. The crystallinity of recovered PHB was in the range of 60 to 65%although a slightly higher crystallinity was observed when the dispersion was used. © 1994 John Wiley & Sons, Inc.
Hydrolysis of triglyceride by the whole cell ofPseudomonas putida3SK in two‐phase batch and continuous reactors systems
Authors: Lee Seoung Yong , Rhee Joon Shick 
Published: December 2004

AbstractBatch and continuous hydrolysis of olive oil in an organic‐aqueous two‐phase system using the live whole cell ofPseudomonas putida3SK as a source of a lipase is investigated. The strain was not only fully viable and grown well, but also produced extracellular lipase simultaneously. The degree of hydrolysis, depending on olive oil concentration in the solvents, was maximal at 13.5% (w/v) and decreased with the increase of the substrate concentration. At the optimal condition, a degree of hydrolysis higher than 95% was achieved with 24 h at 30°C when the reaction was carried out in a two‐phase batch stirred reactor. For long‐term operation a continuous stirred reactor was designed. When the reaction was carried out in a continuous stirred reactor, the degree was hydrolysis reached 86% at a dilution rate of 0.2 h−1. Satisfactory performance of a two‐phase bioreactor was obtained in a long‐term continous operation, which lasted for at least 30 days by feeding organic solvent containing olive oil and aqueous media separately. © 1994 John Wiley & Sons, Inc.
Partitioning of pristinamycins in aqueous two‐phase systems: A first step toward the development of antibiotic production by extractive fermentation
Authors: Paquet V. , Myint M. , Roque C. , Soucaille P. 
Published: December 2004

AbstractThe partitioning of pristinamycins was studied in dextran and polyethylene glycol (PEG) aqueous two‐phases systems. Pristinamycins partitioned preferentially into the PEG‐rich top phase. The partition coefficient was independent of molar mass of PEG and dextran and of antibiotic concentration, but, increased exponentially with the tieline length of the system. Partition of pristinamycins was greatly improved when fatty acids esters of PEG were mixed with PEG. In such mixtures, the partition of coefficient increased up to a value of 24, dependent on the carbon chain length of fatty acids and the modified PEG concentrations. Moreover, in such system, the two groups of pristinamycins, I and II, were extracted in accordance with their hydrophobicity. Recovery of pristinanamycins produced by Streptomyces pritinaespiralis in a fermentation broth was achieved with a dextran/PEG system. Cells were confined into the bottom phase and pristinamycins partitioned in the top phase. However, due to binding of the pristinamycins to the cells, the partition coefficient was slightly lower than of pure antibiotics solutions. © 1994 John Wiley & Sons, Inc.
Foaming and cell flotation in suspended plant cell cultures and the effect of chemical antifoams
Authors: Wongsamuth Raviwan , Doran Pauline M. 
Published: December 2004

AbstractFoam development and stability in Atropa belladonna suspensions were investigated as a function of culture conditions. Foaming was due mainly to properties of the cell‐free broth and was correlated with protein content; effects due to presence of cells increased towards the end of batch culture. Highest foam levels were measured 11 days after inoculation. Air flow rate was of major importance in determining foam volume; foam volume and stability were also strongly dependent on pH. Foam flotation of plant cells was very effective. After 30 min foaming, ca. 55% of cells were found in the foam; this increased to ca. 75% after 90 min. Polypropylene glycol 1025 and 2025, Pluronic PE 6100, and Antifoam‐C emulsion were tested as chemical antifoams. Polypropylene glycol 1025 and Antifoam C at concentrations up to 600 ppm had no adverse effect on growth in shake flasks; Pluronic PE 6100 has an inhibitory effect at all levels tested. Concentrations of polypropylene glycol 2025 and Pluronic PE 6100 as low as 20 ppm reduced foam volumes by a factor of ca. 10. Addition of antifoam reduced kLa values in bubble‐column and stirred‐tank bioreactors. After operation of a stirred reactor for 2 days using Antifoam C for foam control, cell production was limited by oxygen due to the effect of antifoam on mass transfer. Theoretical analysis showed that maximum cell concentrations and biomass levels decline with increasing reactors working volume due to greater consumption of antifoam to prevent foam overflow. The results indicate that when chemical foam control is used in plant cell cultures, head‐space volume and tolerable foam levels must be considered to optimize biomass production. © 1994 John Wiley & Sons, Inc.
Transport of bacteria in porous media: II. A model for convective Transport and growth
Authors: Sarkar A. K. , Georgiou George , Sharma Mukul M. 
Published: December 2004

AbstractA model is presented for the coupled processes of bacterial growth and convective transport of bacteria has been modeled using a fractional flow approach. The various mechanisms of bacteria retention can be incorporated into the model through selection of an appropriate shape of the fractional flow curve. Permeability reduction due to pore plugging by bacteria was simulated using the effective medium theory. In porous media, the rates of transport and growth of bacteria, the generation of metabolic products, and the consumption of nutrients are strongly coupled processes. Consequently, the set of governing conservation equations form a set of coupled, nonlinear partial differential equations that were solved numerically. Reasonably good agreement between the model and experimental data has been obtained indicating that the physical processes incorporated in the model are adequate. The model has been used to predict the in situ transport and growth of bacteria, nutrient consumption, and metabolite production. It can be particularly useful in simulating laboratory experiments and in scaling microbial‐enhanced oil recovery or bioremediation processes to the field. © 1994 John Wiley & Sons, Inc.
Enzymatic hydrolysis of whey proteins: I. Kinetic models
Authors: Gonzàlez‐Tello P. , Camacho F. , Jurado E. , Páez M. P. , Guadix E. M. 
Published: December 2004

AbstractWe have studied the enzymatic hydrolysis of whey proteins at pH 8 and50°C with two proteases of bacterial origin, MKC Protease 660 L, and one of animal origin, PEM 2500 S. Our results show that a greater degree of hydrolysis is achieved under the same experimental conditions with the bacterial proteases than with the animal one. In our interpretation of the results we propose a mechanism in which the hydrolytic reaction is a zero‐order one for the substrate, and the enzyme denaturalizes simultaneously via a second‐order kinetic process due to free enzyme attacking enzyme bound to the substrate. Our results also indicate that there is an irreversible serine‐protease inhibitor in whey proteins. © 1994 John Wiley & Sons, Inc.
Influence of strain and medium composition on filtration of escherichia coli suspensions
Authors: Junker B. H. , Timberlake S. , Bailey F. J. , Reddy J. , Prud'homme R. , Gbewonyo K. 
Published: December 2004

AbstractCross‐flow filtration of Escherichia coli strains was examined at the laboratory and pilot scales using Romicon 500,000 molecular‐weight‐cutoff hollow fiber membranes. Both the series resistance and macrosolute polarization models were employed to compare performances. Total dissolved solids content above 90 g/L and viscosity above 1.1 × 10−3 paċ s of cell‐free culture media were found to decrease average filtration fluxes by over 60% both in the absence and presence of cells. Broth filtration with culture media of dissolved solids levels below 80 g/L were influenced to a greater extent by harvest cell density. The collodial nature of the complex nutrient responsible for the total solids increase affected prediction of filtration performance. Differences in strain filterability were observed with JM109 preferred over DH5 in high solids‐containing media and RR1 preferred over JM109 in low dissolved solids‐containing media. Their research demonstrates the importance of cell strain and media selection in the performance of early downstream processing steps. © 1994 John Wiley & Sons, Inc.
Real and pseudo oxygen gradients in Ca‐alginate beads monitored during polarographic Po2‐measurements using Pt‐needle microelectrodes
Authors: Müller W. , Winnefeld A. , Kohls O. , Scheper T. , Zimelka W. , Baumgärtl H. 
Published: December 2004

AbstractPolarographic microcoaxial needle electrodes were used to measure internal profiles of dissolved oxygen tension (Po2) within single Ca‐alginate beads of different diameter containing entrapped cells of Saccharomyces cerevisiae. For the investigations, single beads coming from variable growing conditions and distinct cultivation stages were fixed in a special holding device. In dependence on microbial growth steep oxygen gradients were observed. The Oxygen penetration depth at steady state lay between 50 and 100 μm. After 8 h of cultivation time, the anaerobic space within the beads (ϕ 2 mm; cultivation in a packed bed reactor) is beginning at ∼ 130 μm, whereas the anaerobic space within the beads (ϕ 2 mm) coming from the shaker flask culture is located ∼440 μm below the bead surface. Surprisingly, steep gradients were also observed, when recording profiles from cell‐free Ca‐alginate beads of different diameter and alginate concentrations. The steep oxygen gradients apparently had to be interpreted as pseudo‐Po2‐gradients. These results were borne by several effects, such as formation of artifacts and diffusion barriers in front of the electrode tip or oxygen “availability” at the tip and consumption of oxygen by the electrode itself. These phenomena could be documented by microscopic observation and photography. Thus, to obtain real Po2‐profiles it is important to be exactly informed about the physical, chemical, and biological properties of the material to be investigated. Furthermore, it is necessary to apply a special stepwise puncture technique with distinct step‐in/step‐out movements of the electrode: e.g., unidirectional or contradirectional puncture techniques. © 1994 John Wiley & Sons, Inc.
On the use of mild hydrophobic interaction chromatography for “method scouting” protein purification strategies in aqueous two‐phase systems: A study using model proteins
Authors: Huddleston J. G. , Wang R. , Lyddiatt A. 
Published: December 2004

AbstractThe behavior of a series of pure proteins partitioned in aqueous two‐phase systems is compared with their behavior during mild hydrophobic interaction chromatography (HIC). A simple theoretical rationale for this comparison is presented based upon solvophobic theory. Similarities were found in the behavior of the model proteins in the two forms of partition chromatography. This indicates that HIC may be employed as a rapid instrumental technique for the broad characterization of protein behavior, which may be of benefit in the development of liquid‐liquid partitioning strategies. However, it has proved difficult to completely account for this behavior on the basis of the known physical and structural properties of the proteins used. The variety in the detailed partitioning behavior of this small sample of protein types suggests that partition in aqueous two‐phase systems is uniquely sensitive to subtle differences in surface properties of complex macromolecules. © 1994 John Wiley & Sons, Inc.
A quantitative analysis of shear effects on cell suspension and cell culture of perilla frutescens in bioreactors
Authors: Zhong Jian‐Jiang , Fujiyama Kazuhito , Seki Tatsuji , Yoshida Toshiomi 
Published: December 2004

AbstractThe short‐time effects of shear on suspended cells of Perilla frutescens were quantitatively analyzed by exposing the cells to a well‐defined flow field in a rotating drum reactor. It was found that both shear rate and shearing time significantly affected cell viability. The quantitative effects of shear on cell growth and the production of anthocyanin, a secondary metabolite, by the cell cultures were further investigated in a series of batch cultivations using a 5‐L plant cell bioreactor with a marine impeller. The results indicated that there was an optimum range of shear rate; i.e., an average shear rate of 20 to 30 s−1 or an impeller tip speed of 5 to 8 dm/s, which maximized all the values of the following parameters: the specific growth rate, the maximum cell concentration, the (specific) production and productivity of anthocyanin, and the cell and anthocyanin yields. © 1994 John Wiley & Sons, Inc.
Separation of amino‐acid enantiomers using micellar‐enhanced ultrafiltration
Authors: Creagh A. L. , Hasenack B. B. E. , Van der Padt A. , Sudhölter E. J. R. , Van't Riet K. 
Published: December 2004

AbstractMicellar‐enhanced ultrafiltration (MEUF) is investigated as a large‐scale technique for separating amino acid enantiomers. Specifically, L‐5‐cholesterol glutamate, a chiral ligand‐exchange cosurfactant, is used together with a nonionic surfactant to form mixed micelles that preferentially bind D‐phenylalanine over L‐phenylalanine in the presence of copper(II). Operational selectivities as high as 4.2 are obtained. Potentiometric titrations using a water‐soluble model compound similar to the chiral cosurfactant indicate that the ternary copper complex with phenylalanine has a stereoselectivity for the D enantiomer which is significantly smaller than that observed in the MEUF system. Thus, the selectivity of the chiral legend's local solvent and structural environment. © 1994 John Wiley & Sons, Inc.
Behavior of spores of Penicillium roquefortii during fed‐batch bioconversion of octanoic acid into 2‐heptanone
Authors: Larroche C. , Besson I. , Gros J. B. 
Published: December 2004

AbstractThe bioconversion of octanoic acid into 2‐heptanone by spores of Penicillium roquefortii is performed using a fed‐batch technique with pH control by addition of the liquid substrate itself. The early stage of this process takes place with a high bioconversion rate and high yield. These values then decrease as a result of germination and growth the biocatalyst. An optimization strategy for the process would thus be to improve the characteristics of this first period, i.e., increase its duration and the reaction rate. An increase in duration is evidenced in two cases: (I) under oxygen limitation: and (ii) when the spore content in the medium is less than 107 spores/mL. These conditions give insufficient overall bioconversion rates: better optimization should be achieved without oxygen limitation and with high spore content. Characterization of the first period by material and bioenergetic balances suggests that an increase in the ethanol content of the medium, which acts as an energy source and a permeabilizer, and the use of specific inhibitor of the Krebs cycle, may be a way to further improve the biocatalyst performance and stability. © 1994 John Wiley & Sons, Inc.
Cell death in bioreactors: A role for apoptosis
Authors: Singh R. P. , Al.‐Rubeai M. , Gregory C. D. , Emery A. N. 
Published: December 2004

AbstractThe incidence of apoptotic and necrotic cell death was compared in CHO, SF9 insect cells and murine plasmacytoma (J558L) and hybridoma (TB/C3) cells during in vitro cultivation in batch cultures. Acridine orange staining and fluorescence microscopy enabled the visualization of a classic morphological feature of apoptotic cell, the presence of condensed and/or fragmented chromatin. DNA gel electrophoresis was employed to show an additional characteristic of the process, the endonuclease‐mediated fragmentation of DNA into multiples of 180 base pairs. The levels of apoptosis at the end of batch cultures of plasmacytoma and hybridoma cell lines were found to be 60% and 90% of total dead cells, respectively. However, employing the above‐mentioned techniques, the biochemical and morphological features of apoptosis were not found in CHO and SF9 insect cells. Some factors affecting the induction of apoptosis during the batch culture of the hybridoma and plasmacytoma cell lines were identified. The most effective inducer was found to be glutamine limitation, followed by (in order of importance) serum limitation, glucose limitation, and ammonia toxicity. Blockage of the cell cycle of the plasmacytoma and hybridoma cells using thymidine resulted in the induction of apoptosis. This has important implications for the development of cell culture processes that minimize cell division and thereby increase specific productivity. © 1994 John Wiley & Sons, Inc.
Characterization of a recombinant antibody produced in the course of a high yield fed‐batch process
Authors: Robinson D. K. , Chan C. P. , Yu Lp C. , Tsai P. K. , Tung J. , Seamans T. C. , Lenny A. B. , Lee D. K. , Irwin J. , Silberklang M. 
Published: December 2004

AbstractMany mammalian cell fed‐batch processes rely on maintaining the cells in a viable and productive state for extended periods of time in order to reach high final concentrations of secreted protein. In the work described herein, a nonamplified NSO cell line was transfected with a vector expressing a recombinant human anti‐HIV gp 120 monoclonal antibody (Mab) and a selectable marker, glutamine synthetase. A fed‐batch process was developed which improved product yields tenfold over the yields reached in batch culture. In this case, the clone was cultured for a period of 22 days and produced 0.85 g Mab/L. To gauge the effect of extended culture lifetime on product quality, biochemical characteristics of MAb isolated from different time points in the fed‐batch culture were determined. The apparent molecular weight of the MAb was constant throughout the course of the culture. Isoelectric focusing revealed four major charged species, with a fifth more acidic species appearing later in the culture. The antigen binding kinetics were constant for MAb isolated throughout the culture period. Glycosylation analysis, on the other hand, revealed that MAb produced later in the culture contained greater percentages of truncated N‐acetylglucosamine and highmannose N‐glycans. Possible contributions to this underglycosylated material from either cell lysis or synthesis from noviable cells were found to be negligible. Instead, the viable cells appeared to be secreting more truncated and high mannose MAb glycoforms as the culture progressed. © 1994 John Wiley & Sons, Inc.
Improving protein extraction yield in reversed micellar systems through surface charge engineering
Authors: Pires M. J. , Martel P. , Baptista A. , Petersen S. B. , Willson R. C. , Cabral J. M. S. 
Published: December 2004

AbstractThe mechanism of extraction of rat cytochrome b5 from water into a sodium dioctylsulfosuccinate (AOT) micellar organic phase was studied using protein engineering of surface charged residues. The extraction behavior of native cytochrome b5 and modified proteins with substitutions of the type glutamic acid → lysine at positions 44 (E44K), 56 (E56K), and 92 (E92K), was studied as a function of pH. The results indicate that an important mechanism of extraction is an electrostatic interaction of this protein with the negatively charged surfactant. We demonstrate that it is possible to improve extraction by engineering the protein surface charge, increasing the driving force responsible for the protein transfer to the micellar phase. © 1994 John Wiley & Sons, Inc.