bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of membrane morphology and operation on protein deposition in ultrafiltration membranes
Authors: Chen V. , Kim K. J. , Fane A. G. 
Published: December 2004

AbstractMembrane morphology is compared to protein depostion under passive adsorption and ultrafiltration conditions. Solute resistance of protein deposits for membranes of varying roughness, structure, and permeability can vary dramatically with operating conditions. Using Brunauer–Emmett–Teller adsorption isotherm (BET), study of the internal area and accessibility of several uttrafiltration membranes to protein deposition allows better understanding of the fouling mechanisms and interpretation of adsorbed protein quantities. © 1995 John Wiley & Sons, Inc.
Effect of insulin on a serum‐free hybridoma culture
Authors: Zhou Weichang , Hu Wei‐Shou 
Published: December 2004

AbstractInsulin is often included in serum‐free media for animal cell cultivation. However, the necessity of insulin for a specific cell line is rather uncertain. In this article we report the effects of insulin on the cultivation of a hybridoma cell line in a serum‐free medium. It was found that insulin affected neither the cell growth nor the antibody production. The specific growth rate and specific antibody production rate were very similar in the cultures with or without insulin. However, the presence of insulin affected the nutrient consumption rate and cell metabolism. Including insulin in the medium resulted in a higher specific glucose consumption rate, a shorter exponential growth stage, and a lower final antibody concentration. The elimination of insulin from the medium allowed antibody to accumulate to a concentration substantially higher than that in the insulin‐containing cultuvre. © 1995 John Wiley & Sons, Inc.
Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium spirulina platensis
Authors: Watanabe Yoshitomo , de la Noüe Joël , Hall David O. 
Published: December 2004

AbstractThe photosynthetic performance of a helical tubular photobioreactor (“Biocoil”), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25‐m2basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6‐cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m2) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air‐lift system ncorporating 4%CO2 was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g · d biomass/L · day, or 5.44 g · d biomass/m2(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO2 was efficiently removed from the gaseous stream; monitoring the CO2 the outlet and inlet gas streams showed a 70% removal of CO2 from the inlet gas over an 8‐h period with almost maximum growth rate. © 1995 John Wiley & Sons, Inc.
Crossflow filtration of baker's yeast with periodical stopping of permeation flow and bubbling
Authors: Tanaka Takaaki , Itoh Hiroshi , Itoh Kazutaka , Nakanishi Kazuhiro , Kume Takaaki , Matsuno Ryuichi 
Published: December 2004

AbstractThe periodical stopping of permeation flow was applied to increase the permeation flux in crossflow filtration of commercially available baker's yeast cell suspension. The permeation flux after 3 h filtration in the crossflow filtration increased to 8 × 10−5 m3 /m2 s (290 L/m2 h) from 2 × 10−5 m3/m2 s (72 L/m2 h) by applying the periodical stopping of permeation. Introduction of air bubbles during the stopping period of permeation further increased the flux.© John Wiley & Sons, Inc.
Effects of p‐cresol and chlorophenols on pentachlorophenol biodegradation
Authors: Gu Yongxiang , Korus Roger A. 
Published: December 2004

AbstractThe effects of three aromatic compounds, p‐cresol, 2,4‐dichlorophenol (DCP), and 2,4,6‐trichlorophenol (TCP), on cell growth and pentachlorophenol (PCP) degradation bya Flavobacterium species were investigated. While p‐cresol was not degraded by this bacterium, DCP and TCP were simultaneously degraded with PCP. Both DCP and TCP lowered cell growth and PCP degradation rate. Cell growth was modeled by cell death, because p‐cresol, DCP, and TCP were toxic to the organism. A new model was used to predict cell death rate in a mixture of two toxic compounds from the cell death kinetics for each individual compound. PCP degradation rates were modeled by conventional inhibition models, but only over a small concentration range for the secondary toxic compound. However, a new empirical model described PCP degradation over a wider concentration range of the secondary toxic compound. © 1995 John Wiley & Sons Inc.
Determination of effective diffusion coefficients and distribution constants in polysaccharide gels with non‐steady‐state measurements
Authors: Øyaas Jorun , Storrø Ivar , Lysberg Magne , Svendsen Hallvard , Levine David W. 
Published: December 2004

AbstractA non‐steady‐state method has been used for determining the effective diffusion coefficient, De, and a distribution constant, Ki, of small molecules in alginate gel beads. A mathematical model based on Pick's law and includingexternal film diffusion resistance describe the diffusion process. Criticalexperimental parameters for the estimation of De and Ki, for both one‐ and two‐parameter methods were the initial solute concentration in the bulk liquid, the void fraction inthe reactor, and the experimental starting point. In our analysis, the two‐parameter method is preferable. Incorporation of an estimate of the film resistance into the overall model increased the estimated values of De significantly and improved the stability of the term over a range of reactor agitation rates. © 1995 John Wiley & Sons Inc.
Modeling of continuous Ph‐stat stirred tank reactor with Lactococcus lactis ssp. lactis bv. diacetylactis immobilized in calcium alginate gel beads
Authors: Cachon Rémy , Molin Paul , Diviès Charles 
Published: December 2004

AbstractA dynamic diffusion–reaction–growth model is proposed for the study of lactic fermentation, the bioconversion of citric acid, and cell release in an immobilized cell reactor [pH‐stat continuous stirred tank‐reactor (CSTR)]. The model correctly simulates the onset of fermentation and colonization of the gel, followed by the steady state. External diffusion is nonlimiting and internal diffusion is limited by high cell densities at the periphery of the gel beads. Lactose–citrate cometabolism in the gel is related to the distribution of active included biomass within the gel and to gradients of substrates (lactose, citrate) and products (lactate, pH) in the beads. The utilization of lactose is limited by reaction, whereas that of citrate is limited by diffusion. Cell release from gel to the liquid medium occurs in the external spherical cap of the beads. In this peripheral zone viability is maintained at around 90%. © 1995 John Wiley & Sons Inc.
Importance of spore mutants for fed‐batch and continuous fermentation of Bacillus subtilis
Authors: Oh M. K. , Kim B. G. , Park S. H. 
Published: December 2004

AbstractTo alleviate plasmid instability and to prolong the production phase of subtilisin, integrable plasmid and spore mutants are used. Compared with batch‐type shake flask cultures, spore mutants' ability to produce subtilisin can be well pronounced in fed‐batch and continuous cultures. Hence, the two culture methods make it possible to identify the peculiar characteristics of the spore mutants unobtainable in batch culture. Spore mutants can enhance subtilisin productivity and prolong subtilisin production time in fed‐batch culture as well as enable us to use very low dilution rates (<0.1 h−1) without losing productivity in continuous culture, thereby improving the conversion yield of the nitrogen source. At 0.05 h−1 the spollG mutant of Bacillus subtilis DB104 (Δnpr Δapr) (Emr) spollG (Bimr):: pMK101 (Cmr) showed a subtilisin yield about ten times higher than that from wild‐type DB104 (Δnpr Δapr)::pMK101 (Cmr). © 1995 John Wiley & Sons, Inc.
Enzyme‐mediated proteolysis of fibrous biopolymers: Dissolution front movement in fibrin or collagen under conditions of diffusive or convective transport
Authors: Anand Sriram , Wu Jung‐He , Diamond Scott L. 
Published: December 2004

AbstractA numerical model based on the convective‐diffusive transport of reacting and adsorbing proteolytic enzymes within erodible fibrous biopolymers was used to predict lysis fronts moving across biogels such as fibrin or collagen. The fiber structure and the transport properties of solutes in fibrin (or collagen) were related to the local extent of dissolution within the dissolving structure. An accounting for solubilization of adsorbed species into solution from the eroding fiber phase provided for complete conservation of mass in reacting systems containing over 10 species. At conditions of fibrinolysis typical of clinical situations, the model accurately predicted the dynamic rate of lysis front movement for plasmin, urokinase, and tissue plasminogen activator (tPA)‐mediated lysis of fibrin gels measured in vitro. However, under conditions of extremely fast fibrinolysis using high enzyme concentrations, fibrinolytic fronts moved very rapidly (>0.1 mm/mm)—faster than predicted for diffusionlimited reactions—at nearly constant velocity for over 2 h, indicating non‐Fickian behavior. This was due to proteolysis‐mediated retraction of dissolving fibrin fibers that resulted in fiber convection and front‐sharpening within 3 μm of the reaction front, as observed by digitally enhanced microscopy. In comparing the model to fibrinolysis measurements using human lys77‐plasmin, the average first order rate constant for non‐crosslinked fibrin bond cleavage by fibrin‐bound plasmin was calculated to be 5s−1 assuming that 10 cleavages per fibrin monomer were required to solubilize each monomer. The model accurately predicted lysis front movement using pressure‐driven permeation of plasmin or urokinase into fibrin as well as literature data obtained under well‐ mixed conditions for tPA‐mediated fibrinolysis. This numerical formulation provides predictive capability for optimization of proteolytic systems which include thrombolytic therapy, wound healing, controlled drug release, and tissue engineering applications. © 1995 John Wiley & Sons, Inc.
Immobilization and properties of carminomycin 4‐O‐methyltranferase, the enzyme which catalyzes the final step in the biosynthesis of daunorubicin in Streptomyces peucetius
Authors: Scotti Claudio , Hutchinson C. Richard 
Published: December 2004

AbstractThe carminomycin 4‐O‐methyltransferase enzyme from Streptomyces peucetius was covalently immobilized on 3M Emphaze ABI‐activated beads. Optimal conditions of time, temperature, pH, ionic strength, enzyme, substrate (carminomycin), and cosubstrate (S‐adenosyl‐L‐methionine) concentrations were defined for the immobilization reaction. Protein immobilization yield ranged from 52% to 60%. Including carminomycin during immobilization had a positive effect on the activity of the immobilized enzyme but a strongly negative effect on the coupling efficiency. The immobilized enzyme retained at least 57% of its maximum activity after storage at 4°C for more than 4 months. The properties of the free and immobilized enzyme were compared to determine whether immobilization could alter enzyme activity. Both soluble and bound enzyme exhibited the same pH profile with an optimum near 8.0. Immobilization caused an approximately 50% decrease in the apparent Km (K′m) for carminomycin while the K′m for S‐adenosyl‐L‐methionine was approximately doubled. A 57% decrease in the Vmax value occurred upon immobilization. These changes are discussed in terms of active site modifications as a consequence of the enzyme immobilization. This system has a potential use in bioreactors for improving the conversion of carminomycin to daunorubicin. © 1995 John Wiley & Sons, Inc.
Mutant Escherichia coli penicillin acylase with enhanced stability at alkaline pH
Authors: del Río Gabriel , Rodríguez Maria‐Elena , Munguía Maria‐Elena , LóPez‐Munguí Agustín , Soberón Xavier 
Published: December 2004

AbstractIncreased stability at alkaline pH should be a valuable attribute for the utilization of penicillin acylase in bioreactors employed to convert penicillins into 6‐aminopenicillanic acid, a precursor of semisynthetic penicillins. In these systems, base is added for pH control, which results in local alkaline conditions that promote enzyme inactivation. Hydrolysis and synthesis reactions are also pH dependent. Here, we report work in which the gene coding for Escherichia coli penicillin acylase was subjected to oligonucleotide‐directed random mutagenesis at regions coding for amino acids predicted to be at the surface of the enzyme. The resulting mutant library, cloned in E. coli, was screened by a filter paper assay of the colonies for the presence of penicillin acylase activity with enhanced stability at alkaline pH. Characterization of one of the selected clones revealed the presence of a mutation, Trp431‐Arg, which would presumably alter the surface charge of the protein. In vitro experiments demonstrated a near twofold increase in the half‐life of the mutant enzyme when stored at pH 8.5 as compared with the wild‐type enzyme, with a comparable specific activity at several pH values. In general, the mutant displayed increased stability toward the basic side in the pH‐stability profile. © 1995 John Wiley & Sons, Inc.
Hybridoma growth and antibody production as a function of cell density and specific growth rate in perfusion culture
Authors: Banik Gautam G. , Heath Carole A. 
Published: December 2004

AbstractSteady state metabolic parameters for hybridoma cell line H22 were determined over a wide range of cell densities and specific growth rates in a filtration based homogeneous perfusion reactor. Operating the reactor at perfusion rates of 0.75, 2.0, and 2.9 day−1(each at four different specific growth rates), viable cell densities as high as 2 × 107 cells/mL were obtained. For the cell line under investigation, the specific monoclonal antibody production rate was found to be a strong function of the viable cell density, increasing with increasing cell density. In contrast, most of the substrate consumption and product formation rates were strong functions of the specific growth rate. Substrate metabolism became more efficient at high cell densities and low specific growth rates. The Specific rates of metabolite formation and the apparent yields of lactate from glucose and ammonia from glutamine decreased at low specific growth rates and high cell densities. While the specific oxygen consumption rate was independent of the specific growth rate and cell density, ATP production was more oxidative at lower specific growth rate and higher cell density. These observed shifts are strong indications of the production potential of high‐density perfusion culture. © 1995 John Wiley & Sons, Inc.
Metal affinity protein precipitation: Effects of mixing, protein concentration, and modifiers on protein fractionation
Authors: Iyer Harish V. , Przybycien Todd M. 
Published: December 2004

AbstractPrevious work by us and others has shown that mixing impacts apparent protein solubility in single protein precipitations. In this work, we probe the effects of contacting conditions on fractional precipitation behavior at the bench scale. We have chosen metal affinity precipitation as our model system; the kinetics of this mode of precipitation are very rapid and largely irreversible and, consequently, mixing conditions govern the extent of fractionation and purity of the product in such a process. Our experimental strategy involved a three‐pronged approach to control the effects contacting conditions on precipitate yield, purity, and particle size distribution. First, we studied the impact of process variables that control precipitant concentrations in the reactor including impeller speed and precipitant addition rate. Second, we controlled the rate of precipitation by changing the initial protein concentration to alter the protein‐protein collision rate. Third, we examined the role of the molecular‐level kinetics of affinity precipitation by using modifiers that compete with surface moieties to bind the metal ion, thereby reducing its availability. Our model process and protein system consisted of zinc precipitations of mixtures of bovine serum albumin and bovine γ‐globulins, carried out at a nominal 1‐L scale; glycine was examined as a modifier. Faster impeller speeds and lower precipitant addition rates increased the desired protein yields, decreased purities, and reduced average precipitate particle size. Higher initial protein concentrations were found to produce precipitates with higher yields, lower purities and diminished particle size. Experiments with glycine indicated that modifiers in the precipitant solution serve to increase product purity, decrease yield, and increase the average particle size in bench‐scale precipitations. © 1995 John Wiley & Sons, Inc.
Microfiltration of yeast suspensions with self‐cleaning spiral vortices: Possibilities for a new membrane module design
Authors: Mallubhotla Hanuman , Nunes Elizabeth , Belfort Georges 
Published: December 2004

AbstractA novel method of producing controlled vortices was used to reduce both concentration polarization and membrane fouling during microfiltration of Saccharomyces cerevisiae broth suspensions. The method involves flow around a curved channel at a sufficient rate so as to produce centrifugal instabilities (called Dean vortices). These vortices depolarize the build‐up of suspended particles such as yeast cells at the membrane‐solution interface and allow for increased membrane permeation rates. Various operating conditions under which such vortices effectively reduced cake build‐up of suspended particles such as yeast cells at the membrane‐solution interface and allow for increased membrane permeation rates. Various operating conditions under which such vortices effectively reduced cake build‐up during microfiltration of 0 to 0.55 dry wt% yeast broth were investigated. Flux improvements of over 60% for 0.25 dry wt% yeast broth for flow with over that without Dean vortices were observed. This beneficial effect increased with increasing retentate flow rate and increasing transmembrane pressure and decreased with increasing concentration of suspended matter. Similar behavior was observed whether the cells were viable of killed. the improvement in flux in the presence over that in the absence of vortices correlated well with centrifugal force or azimuthal velocity squared. The relative cake resistances increased with reservoir yeast concentration. These values with vortices increased from 62% to 75% of that without vortices with increasing yeast concentration. The ratio of the cake thicknesses in the limiting case (at high feed concentration) was 3.25. These results suggest that self‐cleaning spiral vortices could be effective in maintaining good and steady microfiltration performance with cell suspensions other than those tested. © 1995 John Wiley & Sons, Inc.
Degradation of wild‐type alpha‐synuclein by a molecular chaperone leads to reduced aggregate formation
Authors: Kong Byungmoon , Chae Youngkee , Lee Kyunghee 
Published: December 2004

AbstractAlpha‐synuclein, a presynaptic protein, was found to be the major component in the Lewy bodies (LB) in an age‐related neurodegenerative disease, Parkinson's disease (PD). Even though the function of alpha‐synuclein is not completely understood, it has been demonstrated to spontaneously aggregate into amyloid fibrils. With the aim of inhibiting aggregate formation, a molecular chaperone protein, Hsp104p, was investigated since it rescues cells from stress by resolubilizing denatured proteins from insoluble aggregates, in vivo as well as in vitro. Here, in order to examine whether Hsp104p functions as a regulator of aggregate formation for alpha‐synuclein, we expressed the His‐tagged wild‐type (wt) synuclein and the glutathione‐S‐transferase (GST)‐tagged Hsp104p in bacterial systems. Using thioflavin‐T fluorescence assays, significant protection against fibril formation was observed with wt Hsp104p regardless of the presence of ATP, but not with mutant Hsp104p. To a lesser extent, the dissociation effect of wild‐type Hsp104p was observed only in the presence of ATP. Interaction between Hsp104p and synuclein was also investigated using a GST pull‐down experiment. Interestingly, Hsp104p degraded alpha‐synuclein in a concentration‐dependent manner with the synergistic assistance of ATP. These results suggest that Hsp104p could be developed as a therapeutic candidate in the treatment of protein aggregation‐related neurodegenerative disease. Copyright © 2004 John Wiley & Sons, Ltd.
Zur Analyse von Nitriersäuren
Authors: Kortüm G. 
Published: December 2004

AbstractDas indirekte Verfahren, nach dem Phosphat‐ bzw. Fluor‐lonen durch die Extinktionsabnahme des Eisensalicylat‐Komplexes bestimmt werden, kann auch für die Bestimmung der Schwefelsäure in Nitriersäure‐Gemischen nutzbar gemacht werden.
Zur Bemessung von Vakuumleitungen
Authors: Harries W. 
Published: December 2004

AbstractFehler in der Bemessung von Vakuumleitungen führen im chemischen Betrieb nicht nur zu einer Erhöhung der laufenden Kosten, sondern können auch Anlaß zu Qualitäts minderungen geben, da dann bei höheren Drucken und damit bei unzulässig hohen Temperaturen gearbeitet werden muß. Es werden daher im folgenden Richtlinien für die Bemessung von Vakuumleitungen aufgestellt und an H and eines Nomogrammes erläutert.
Verhalten aktiven Kobalts gegen H2O beim Fischer‐Kontakt
Authors: Schütza Heinz 
Published: December 2004

AbstractBei der technischen Durchführung der Kohlenwasserstoffsynthese nach Fischer‐Tropsch trat unter bestimmten Betriebsbedingungen regelmäßig eine völlige Oxydation einer verhältnismäßig dünnen Lage des Kontaktes am Eingang des Syntheseofens auf, wobei ein Übergangsgebiet von einigen Zentimetern zum normalen, nicht oxydierten Kontakt überleitete. Zur Ergründung und Beherrschung dieses Vorgangs, der auch Einblicke in das Reaktionsgeschehen eines technisch wichtigen aktiven festen Stoffes zu geben versprach, wurde die folgende Untersuchung durchgeführt.
Diffusion, Strömung und Reaktionsgeschwindigkeit im Innern poröser Kontaktkörper
Authors: Wicke E. , Brötz W. 
Published: December 2004

AbstractIn porösen Katalysatorkörnern konkurriert die Geschwindigkeit der chemischen Reaktion an den „inneren”︁ Oberflächen mit der Diffusion der gasförmigen Reaktionspartner zu diesen Reaktionsorten hin. Bei nicht raumbeständigen Reaktionen überlagert sich dem Diffusionstransport eine (hydrodynamische) Porenströmung. Je nach den Geschwindigkeitsverhältnissen dieser miteinander konkurrierenden Vorgänge dringt die Reaktion bis ins Zentrum des Katalysatorkorns vor oder aber nutzt nur randnahe Schichten des Porengefüges für die Katalyse aus. Es stellt sich bezgl. der Konzentrationsverteilung im Korninnern ein stationärer Zustand ein. In der vorliegenden Untersuchung wird dieser Zustand unter isothermen und theoretisch auswertbaren Verhältnissen experimentell erfaßt. Als Modellreaktionen dienen die p‐o‐H2‐Umwandlung und der Methylalkohol‐Zerfall an Ni‐ und ZnO‐Kontakten verschiedenen Porengefüges. Insbesondere werden die Einflüsse des Gesamtdruckes, der Temperatur und von Fremdgaszusätzen auf den Nutzungsgrad poröser Katalysatorproben untersucht und die für die Transportvorgänge innerhalb des Porengefüges maßgebenden freien Diffusionsquerschnitte ermittelt.