bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperosmotic hbridoma cell cultures: Increased monoclonal antibody production with addition of glycine betaine
Authors: Øyaas Karin , Ellingsen Trond E. , Dyrset Nils , Levine David W. 
Published: December 2004

AbstractWhen mouse hybridoma cells were grown in culture media which were made hyperosmotic through the addition of NaCl or sucrose, the specific rate of antibody production increased with medium osmolality, reaching approx. 1.9 times the level obtained at physiological osmolality. However, due to a simultaneous reduction of the maximal cell density in the hyperosmotic media, the effect of the increased production rate did not give significant increases in the maximum antibody titer obtained in the cultures. When the osmoprotective compound, glycine betaine, was included in the NaCl‐ or sucrose‐stressed cultures, the specific antibody production rate wasincreased up to 2.6‐fold and maximum antibody titer up to twofold over that obtained in the control culture (physiological osmolality). A similar pattern of response was observed when other osmoprotective compounds (sarcosine, proline, glycine) were added to NaCl‐stressed hybridoma cell cultures. For the present experiments, the results suggest that medium osmolality, rather than growth rate, will determine the specific antibody production rate by hybridoma cell line 6H11 growing in hyperosmotic culture media. © 1994 John Wiley & Sons, Inc.
On‐line estimation of biological variables during pH controlled lactic acid fermentations
Authors: Acuña Gonzalo , Latrille Eric , Béal Catherine , Corrieu Georges , Chéruy Arlette 
Published: December 2004

AbstractIndirect measurement of lactose, galactose, lactic acid, and biomass concentration from on‐line sodium hydroxide weight measurements have been obtained for pure and mixed batch cultures of Streptococcus salivarius ssp. thermophilus 404 and Lactobacillus delbrueckii subsp. bulgaricus 398 conducted at controlled pH and temperature. Linear correlations were established between the equivalent sodium hydroxide concentration and the lactose (substrate), galactose and lactic acid (products) concentrations while nonlinear relationships were developed between biomass and lactic acid concentrations. These nonlinear relationships took into account the inhibitory effect of lactic acid on growth and acidification. The indirect measurements of biomass concentration were introduced into a nonlinear estimator of the state variables and of the specific growth and lactic acid production rates. Good agreement was found between estimated and measured biomass concentrations (error index ranging from 10.8% to 12.6%). The results showed the feasibility of on‐line estimation of biomass concentration and of the specific kinetics from NaOH addition weight measurements and its applicability for monitoring lactic acid fermentations. Using off‐line measurements of L(+) and D(‐) lactic acid concentrations, the evolution of the concentration of each strain in mixed cultures was obtained from the relationships proposed for the mixed cultures. © 1994 John Wiley & Sons, Inc.
A facile transphosphatidylation reaction using a culture supernatant of actinomycetes directly as a phospholipase D catalyst with a chelating agent
Authors: Nakajima Jan , Nakashima Toshimitsu , Shima Yu , Fukuda Hideki , Yamane Tsuneo 
Published: December 2004

AbstractAn attempt was made to use the phospholipase D (PLD)‐ containing culture supernatants of actinomycetes directly as catalysts for the transphosphatidylation reaction of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in a biphasic system. Of the five actinomycetes (three Streptomyces sp. and two Streptoverticillium sp.) examined, three (St. mediocidicus, Stv. cinnamoneum and Stv. hachijoense) exhibited good PLD production performance, but the selectivity (ratio of transphosphatidylation to hydrolysis) of the PLDs in the culture supernatant of all three actinomycetes were significantly low. However, the addition of EDTA to the reaction mixture as a chelating agent remarkably improved the selectivity of the PLDs, which approached 100% in all the culture supernatants. Commercially available PLDs were also investigated and classified into two types. The PLDs of one type had high selectivity and no metal was required for the enzyme activity, while those of the other type showed low selectivity and a metal was necessary for the enzyme to be activated. From this finding, it was considered that the culture supernatants used in this study contained several PLDs of both types. When the chelating agent was added to the reaction mixture, the hydrolysis due to PLDs with low selectivity was suppressed by removal of the essential metal, resulting in an increased in the overall selectivity of the PLDs in the culture supernatant. Repeated batch transphosphatidylation reactions were performed 20 times, reusing the PLDs in the aqueous phase by centrifugation; the reaction rate gradually decreased to 60% of that of batch 1 by batch 20. This suggests that the transphosphatidylation reaction using a culture supernatant has potential for industrial application. © 1994 John Wiley & Sons, Inc.
Comparison of recombinant Escherichia coli strains for synthesis and accumulation of poly‐(3‐hydroxybutyric acid) and morphological changes
Authors: Lee Sang Yup , Lee Kyung Mi , Chan Ho Nam , Steinbüchel Alexander 
Published: December 2004

AbstractA stable high‐copy‐number plasmid pSYL105 containing the Alcaligenes eutrophus polyhydroxyalkanoic acid (PHA) biosynthesis genes was constructed. This plasmid was transferred to seven Escherichia coli strains (K12, B, W, XL1‐Blue, JM109, DH5α, and HB101), which were subsequently compared for their ability to synthesize and accumulate ploy‐ (3‐hydroxybutyric acid) (PHB). Growth of recombinant cells and PHB synthesis were investigated in detail in Luria‐Bertani (LB) medium containing 20 g/L glucose. Cell growth, the rate of PHB synthesis, the extent of PHB accumulation, the amount of glucose utilized, and the amount of acetate formed varied from one strain to another. XL1‐Blue (pSYL105) and B (pSYL105) synthesized PHB at the fastest rate, which was ca. 0.2 g PHB/g true cell mass‐h, and produced PHB up to 6‐7 g/L. The yields of cell mass, true cell mass, and PHB varied considerably among the strains. The PHB yield of XL1‐Blue (pSYL105) in LB plus 20 g/L glucose was as high as 0.369 g PHB/g glucose. Strains W (pSYL105) and K12 (pSYL105) accumulated the least amount of PHB with the lowest PHB yield at the lowest synthesis rate. JM109 (pSYL105) accumulated PHB to the highest extent (85.6%) with relatively low true cell mass (0.77 g/L). Considerable filamentation of cells accumulating PHB was observed for all strains except for K12 and W, which seemed to be due either to the overexpression of the foreign PHA biosynthesis enzymes or to the accumulation of PHB. © 1994 John Wiley & Sons, Inc.
Immiscible organic solvent inactivation of urease, chymotrypsin, lipase, and ribonuclease: Separation of dissolved solvent and interfacial effects
Authors: Ghatorae Amreek S. , Guerra Maria J. , Bell George , Halling Peter J. 
Published: December 2004

AbstractA new technique with controlled interface generation allows separation and quantitation of enzyme inactivation by both solvent/aqueous interface and dissolved solvent. This has now been used in n‐butanol, isopropylether, 2‐octanone, n‐hexane, n‐butylbenzene, and n‐tridecane. Ribonuclease was stable with all the solvent/aqueous interfaces studied. Chymotrypsin was mainly inactivated by the more hydrophobic solvent/aqueous interfaces, whereas lipase was only inactivated by the less hydrophobic solvent/aqueous interfaces. Urease was inactivated by some interfaces, but not all, without an obvious trend. Thus, the commonly expected simple relationship with solvent polarity (e.g., log P) does not apply when interfacial inactivation is determined specifically. Greater dissolved solvent inactivation occurred with the more polar solvents, though only a general trend was apparent with log P. A better correlation was noted with the Hilde‐brand solubility parameter. Interfacial effects are discussed with reference to enzyme molecular weight, denaturation temperature, hydrophobicity, and adiabatic compressibility. © 1994 John Wiley & Sons, Inc.
The use of hollow fiber cross‐flow microfiltration in bioaccumulation and continuous removal of heavy metals from solution by Saccharomyces cerevisiae
Authors: Brady D. , Rose P. D. , Duncan J. R. 
Published: December 2004

AbstractCross‐flow microfiltration was shown to retain Saccharomyces cerevisiae biomass utilized for heavy metal bioaccumulation. The passage of metal‐laden influent through a series of sequential bioaccumulation systems allowed for further reductions in the levels of copper, cadmium, and cobalt in the final effluent than that afforded by a single bioaccumulation process. Serial bioaccumulation systems also allowed for partial separation of metals from dual metal influents. More than one elemental metal cation could be accumulated simultaneously and in greater quantities than when a single metal was present in the effluent (Cu2+ 0.43 mmol, Cu2+ + Cd2+ 0.67 mmol, and Cu2+ + Co2+ 0.83 mmol/g yeast dry mass when the initial concentration of each of the metal species was 0.2 mmol·L−1). Co‐accumulation of two different metal cations allowed higher total levels of bioaccumulation than found with a single metal. The flux rate was 2.9 × 102 L·h−2μm−2 using a polypropylene microfiltration membrane (0.1 μm pore size) at 25°C. © 1994 John Wiley & Sons, Inc.
Parametric sensitivity of stoichiometric flux balance models applied to wild‐type Escherichia coli metabolism
Authors: Varma Amit , Palsson Bernhard O. 
Published: December 2004

AbstractStoichiometrically based flux balance models provide a method to quantify the metabolic pathway fluxes within a living cell. Predictions of flux balance models are expected to have applications in pathway engineering as well as in bioprocess design and control. These models utilize optimality principles applied to metabolic pathway stoichiometry along with the metabolic requirements for growth to determine the flux distribution in a metabolic network. A flux balance model has been developed for Escherichia coli W3110 using five experimentally determined strain‐specific parameters. In this report, we determine the sensitivity of the predictions of the flux balance model to these five strain‐specific parameters. Model predictions are shown to be sensitive to the two parameters describing metabolic capacity, while they are relatively insensitive to the three parameters that describe the metabolic requirements for growth. Thus, when stoichiometrically based models are formulated for additional strains one needs to measure the metabolic capacity (maximum rates of nutrient and oxygen utilization) accurately. Determination of metabolic capacity from batch experiments is relatively easy to perform. On the other hand, the harder to determine maintenance parameters need not be as accurately determined. © 1995 John Wiley & Sons, Inc.
Working at controlled water activity in a continuous process: The gas/solid system as a solution
Authors: Lamare Sylvain , Legoy Marie Dominique 
Published: December 2004

AbstractFusarium solani cutinase and Candida cylindracea lipase were used to catalyze a transesterification reaction in a continuous gas/solid bioreactor. In this system, a solid phase composed of a packed enzymatic preparation was continuously percolated with carrier gas which fed substrate and removed reaction products simultaneously. Different conditions of immobilization were used and compared to the results obtained with a nonsupported enzyme. The enzymatic activity was found to be highly dependent of a key parameter: water activity (aw). Biocatalyst stability was greatly influenced by water activity and the choice of immobilization technique for the enzymatic material. For free and adsorbed enzymes, water requirements exhibited optima which corresponded to the complete hydration coverage of the protein. These optima presented a good correlation with the isotherm sorption curves obtained for the different preparations. In this work are reported the results concerning the possibility of using a continuous system able to operate at controlled water activity in a heterogeneous medium. Lipolytic enzyme in such a system appears to be a new process for the biotransformation of volatile esters. © 1995 John Wiley & Sons, Inc.
The protective effect of specific medium additives with respect to bubble rupture
Authors: Chattopadhyay Devamita , Rathman James F. , Chalmers Jeffrey J. 
Published: December 2004

AbstractA significant degree of cell damage is observed during suspension cell culture with air sparging. Protective agents can be added to the culture medium to protect the cells from damage. It has been observed that cells tend to adhere to air–medium interfaces and cell damage is mainly due to this cell–bubble interaction; protective additives have been found to prevent this cell adhesion to the bubble surfaces. In this article, it is demonstrated that the interfacial tension between the air and medium is related to the effectiveness of the protective additives to prevent adhesion of cells to this interface. Five different types of additives (Pluronic F‐68, Methocels, dextran, Polyvinyl alcohol, and polyethylene glycols) were studied in an effort to determine their protective characteristics. Liquid–vapor interfacial tensions of the culture medium, with and without the additives, were measured by two different techniques (maximum bubble pressure method and Wilhelmy plate method). In addition, visualization techniques showed that in the presence of certain protective additives cells do not adhere to the bubble surface. Results obtained from these experiments indicate that the additives which rapidly lower the liquid–vapor interfacial tension of the culture medium also prevent adhesion of cells to the bubble surface. Experiments have also been conducted to determine the number of cells killed due to bubble rupture, and it was observed that this number is related to the amount of cells adhering to the bubble surface. © 1995 John Wiley & Sons, Inc.This article is a US Government Work and, as such, is in the public domain in the United States of America.
Continuously coupled transcription‐translation system for the production of rice cytoplasmic aldolase
Authors: Tulin Edgardo E. , Tsutsumi Ken‐ichi , Ejiri Shin‐ichiro 
Published: December 2004

AbstractA continuously coupled cell‐free transcription‐translation system was developed for the production of rice cytoplasmic aldolase, an enzyme involved in both glycolytic and gluconeogenic pathways in eukaryotic cells. The system works with a continous flow of feeding solution containing nucleoside triphosphates and amino acids into a 1‐mL reactor containing wheat‐germ extract, plasmid DNA, and transcription enzyme, and continuous removal of translation product through an ultrafilatration membrane fitted in the reactor. Addition of free nucleotide primer, m7G(5′)ppp(5′)G, to this reactor was necessary for efficient transcription, thus producing biologically active mRNA for translation. The rate of aldolase synthesis was constant during the continuous translation reaction. It was observed that from 3 h onward only aldolase was synthesized by the system. After 30 h, the total amount of protein synthesized reached 205.6 μg, which is comparable with the amount sysnthesized (255.6 μg) in the translation system only where separetaly prepared capped mRNAs were added to the reactor for translation. Autoradiogram and Western blot analyses of the translated product showed a distinct band corresponding to the calculated molecular weight of the protein. These results have shown the establishment of a continuously coupled eukaryotic transcription‐translation system for the expression of genes from eukaryotic cells. © 1995 John Wiley & Sons, Inc.
Occurrences at mineral–bacteria interface during oxidation of arsenopyrite by Thiobacillus ferrooxidans
Authors: Fernandez Marcos G. Monroy , Mustin Christian , de Donato Philippe , Barres Odile , Marion Philippe , Berthelin Jacques 
Published: December 2004

AbstractThe combination of an improved bacterial desorption method, scanning electron microscopy (SEM), diffuse reflectance and transmission infrared Fourier transform spectroscopy, and a desorption‐leaching device like high‐pressure liquid chromatography (HPLC) was used to analyze bacterial populations (adhering and free bacteria) and surface‐oxidized phases (ferric arsenates and elemental sulfur) during the arsenopyrite biooxidation by Thiobacillus ferrooxidans. The bacterial distribution, the physicochemical composition of the leachate, the evolution of corrosion patterns, and the nature and amount of the surface‐oxidized chemical species characterized different behavior for each step of arsenopyrite bioleaching. The first step is characterized by a slow but strong adhesion of bacteria to mineral surfaces, the appearance of a surface phase of elemental sulfur, the weak solubilization of Fe(II), As(III), and As(V), and the presence of the first corrosion patterns, which follow the fragility zones and the crystallographic orientation of mineral grains. After this short step, growth of the unattached bacteria begins, while ferrous ions in solution are oxidized by them. Ferric ions produced by the bacteria can oxidize the sulfide directly and are regenerated by Fe(II) bacterial oxidation. At this time, a bioleaching cycle takes place and a coarse surface phase of ferric arsenate (FeAsO4 · xH2O where x ≈ 2) and deep ovoid pores appear. At the end of the bioleaching cycle, the high concentration of Fe(III) and As(V) in solution promotes the precipitation of a second phase of amorphous ferric arsenate (FeAsO4 · xH2O where x ≈ 4) in the leachate. Then the biooxidation process ceases: The bacteria adhering to the mineral sufaces are coated by the ferric arsenates and the concentration of Fe(III) on the leachate is found to have decreased greatly. Both oxidation mechanisms (direct and indirect oxidation) have been stopped. © 1995 John Wiley & Sons, Inc.
Cell cycle and cell size dependence of susceptibility to hydrodynamic forces
Authors: Al‐Rubeai Mohamed , Singh R. P. , Emery A. N. , Zhang Z. 
Published: December 2004

AbstractExposure of animal cells to intense hydrodynamic forces exerted in turbulent capillary flow, and by controiled agitation and aeration, resulted in preferential destruction of S and G2 cells and the extent of destruction of these cells was dependent upon the intensity of the action. The loss of these cells was possibly due to their larger size. However, the appearance of large numbers of membrane‐bound vesicular structures similar to apoptotic bodies as well as cells with low DNA stainability (in a sub‐G1 peak) suggested that the action of adverse hydrodynamic forces on these large cells may at least in part be to induce an apoptotic response. © 1995 John Wiley & Sons, Inc.
Enzymatic glucosylation of hydrophobic alcohols in organic medium by the reverse hydrolysis reaction using almond‐β‐D‐glucosidase
Authors: Vic Gabin , Biton Jacques , Le Beller Dominique , Michel Jean‐Marc , Thomas Daniel 
Published: December 2004

AbstractAlkyl β‐D‐glucosides were synthesized from D‐glucose and alcohols by reverse hydrolysis using the commercially available almond β‐D‐glucosidase in 9:1 (v/v) acetonitrile–water medium. The main characteristics of this enzyme‐catalyzed glucosylation were established by using 2‐hydroxybenzyl alcohol. The reaction is entirely regio‐ and stereoselective. The solvent plays a fundamental role because, by decreasing the water concentration in the medium, the shift of the reaction equilibrium toward synthesis is realized without using an excessive amount of alcohol. Nevertheless, a minimum amount of water is necessary to maintain the enzyme activity. In contrast to the use of the enzyme in aqueous medium, the pH of the added water in acetonitrile did not influence the synthesis. Using this procedure, we have conducted systematic glucosylation of numerous alcohols and we have investigated enzyme specificity and alcohol reactivity. The enzyme has a pronounced affinity for the alcohols containing a phenyl group, and enantioselectivity for the aglycon is obtained with 1‐phenylethyl alcohol. Moreover, by using almond β‐D‐glucosidase it was also possible to synthesize alkyl β‐D‐galactosides. © 1995 John Wiley & Sons, Inc.
A strategy for construction of industrial strains of distiller's yeast
Authors: Ibragimova S. I. , Kozlov D. G. , Kartasheva N. N. , Sutsov N. I. , Efremov B. D. , Benevolensky S. V. 
Published: December 2004

AbstractA procedure was developed for construction of industrial strains of distiller's yeast (Saccharomyces cerevisiae). It includes several steps: construction of congenic genetically marked haploid strains of opposite mating types starting from an industrial strain of hybrid nature, integrative transformation of the above haploid strains with a DNA fragment containing an expression cassette responsible for new technological facilities, and hybridization of transformants and isolation of final industrial homozygous strains under experimental conditions simulating commercial fermentation processes. This strategy permits the generation of strains that have desirable characteristics of traditional races of distiller's yeast along with new technological facilities determined by the particular expression cassette. Using this procedure, we have constructed an industrial strain with improved amylolytic activity. © 1995 John Wiley & Sons, Inc.
A model that links growth and secondary metabolite production in plant cell suspension cultures
Authors: Guardiola J. , Iborra J. L. , Cánovas M. 
Published: December 2004

AbstractPlant cell suspensions of grape cells (Vitis vinifera L. cv. Gamay Fréaux) were grown in shake flasks operated both in the batch and semicontinuous mode. A mathematical model was developed to describe grape cell growth, sucrose uptake, and secondary metabolite (anthocyanin) production. Parameters were estimated from batch studies data. The model was able to predict results for semicontinuous experiments by only modifying the value of four of these parameters. The modified parameters (maximum specific rate of biomass production, maximum specific rate of substrate consumption for maintenance, maximum specific rate of anthocyanin production, and degradation constant of anthocyanins) were related to the kinetics rather than to the yield of the process. The model introduces the concept of primary and secondary metabolism substrate concentration–dependent competition for precursors. Further, the model was able to predict the evolution of the cell system when substrate is scarce, as the value of the different kinetic constants determines the portion of substrate that is used for biomass production, secondary metabolite production, and cell maintenance. © 1995 John Wiley & Sons, Inc.
Removal of water produced from lipase‐catalyzed esterification in organic solvent by pervaporation
Authors: Kwon Seok Joon , Song Kyu Min , Hong Won Hi , Rhee Joon Shick 
Published: December 2004

AbstractEsterification of oleic acid with n‐butanol in the presence of Lipozyme® was carried out at 25°C in isooctane with various initial water activities. Initial reaction rate as well as equilibrium conversion decreased at high initial water activity. Therefore, removal of water present in the reaction mixtures was essential. A pervaporation process was applied to the lipase‐catalyzed synthesis of n‐butyloleate to remove water. Pervaporation selectively separated water from the reaction mixture using a nonporous polymeric membrane, cellulose acetate. Therefore, pervaporation is potentially applicable to remove the water produced from various enzymatic processes, such as synthesis of various esters, peptides, and glycosides in a solvent system as well as in a solvent‐free system. © 1995 John Wiley & Sons, Inc.