bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biofilm detachment mechanisms in a liquid‐fluidized bed
Authors: Chang H. Ted , Rittmann Bruce E. , Amar D. , Heim R. , Ehlinger O. , Lesty Y. 
Published: December 2004

AbstractBed fluidization offers the possibility of gaining the advantages of fixed‐film biological processes without the disadvantage of pore clogging. However, the biofilm detachment rate, due to hydrodynamics and particle‐to‐particle attrition, is very poorly understood for fluidized‐bed biofilm processes. In this work, a two‐phase fluidized‐bed biofilm was operated under a constant surface loading (0.09 mg total organic carbon/cm2 day) and with a range of bed height (H), fluid velocities (U), and support‐particle concentrations (Cp). Direct measurements were made for the specific biofilm loss rate coefficient (bs)and the total biofilm accumulation (XfLf). A hydrodynamic model allowed independent determination of the biofilm density (Xf), biofilm thickness (Lf), liquid shear stress (τ), and Reynolds number (Re). Multiple regression analysis of the results showed that increased particle‐to‐particle attrition, proportional to Cp and increased turbulence, described by Re, caused the biofilms to be denser and thinner. The specific detachment rate coefficient (bs) increased as Cp and Re increased. Almost all of the 6, values were larger than predicted by a previous model derived for smooth biofilms on a nonfluidized surface. Therefore, the turbulence and attrition of bed fluidization appear to be dominant detachment mechanisms.
Inhibition of microbial growth and metabolism by excess turbulence
Authors: Toma M. K. , Ruklisha M. P. , Vanags J. J. , Zeltina M. O. , Lelte M. P. , Galinine N. I. , Viesturs U. E. , Tengerdy R. P. 
Published: December 2004

AbstractExcess turbulence caused by high‐intensity stirring inhibited microbial growth and metabolism. In stirred tank bioreactors, the growth rate and lysine biosynthesis decreased in Brevibacterium flavum beyond 900 rpm, the growth rate of Trichoderma reesei on wheat straw beyond 150 rpm, and the growth rate of Saccharomyces cerevisae beyond 800 rpm. The term turbohypobiosis was introduced to describe this inhibition. Turbohypobiosis was characterized by a stress factor Fstr expressing the interaction of medium flow with microbial cells in local turbulent zones, dependent on the energy distribution of the stirring regime. Lysine synthesis was inhibited at significantly lower Fstr values than the growth of B. flavum. The main reason for the inhibition was shear effects causing decreased adenosine triphosphate (ATP) generation, lower O2 uptake, and lower specific growth rate of bacteria.
Culture of insect cells in helical ribbon impeller bioreactor
Authors: Kamen A. A. , Tom R. L. , Caron A. W. , Chavarie C. , Massie B. , Archambault J. 
Published: December 2004

AbstractAn 11‐L helical ribbon impeller (HRI) bioreactor was tested for the culture of Spodoptera frugiperda (Sf−9) cells. This impeller and surface baffling ensured homogeneous mixing and high oxygen transfer through surface aeration and surface‐induced babble generation. Serum‐supplemented and serum‐free cultures, using TNMFH and IPL/41 media, respectively, grew a similar specific growth rates(0.031 and 0.028 h−1) to maximum cell densities of 5.5 × 106−6.0 × 106 cells. mL−1 with viability exceeding 98% during exponential growth phase. Growth limitation coincided with glucose and glutamine depletion and production of significant amounts of alanine. The bioreactor was further tested under more stringent conditions by infecting a serum‐free medium culture with a recombinant baculovirus. Heterologous protein production of ∼35 μg per 106 cells was comparable to yields obtained in serum‐free cultures grown in spinner flasks and petri dishes. Average specific oxygen up‐take and carbon dioxide production rates of the serum‐free culture prior to infection as measured by on‐line mass spectroscopy were 0.20 μmol O2μ·(106 cells)−1 h−1 and 0.22 μmol CO2 · (106 cells)−1h−1 and increased by 30–40% during infection. Therefore, the mixing and oxygenation conditions of this bioreactor were suitable for insect cell culture and recombinant protein production, with limitation being mainly attributed to nutrient depletion and toxic by‐product generation.
Enzymatic resolution of (S)‐(+)‐naproxen in a continuous reactor
Authors: Battistel Ezio , Bianchi Daniele , Cesti Pietro , Pina Carlo 
Published: December 2004

AbstractAn enzymatic method for the continuous production of (S)−(+)−2−(6‐methoxy‐2‐naphthyl) propionic acid (Naproxen) has been developed. The process consists of a stereoselective hydrolysis of the racemic Naproxen ethoxyethyl ester catalyzed by Candida cylindracea lipase. The reaction has been carried out in a continuous‐flow closed‐loop column bioreactor packed with Amberlite XAD−7, a slightly polor resin on which the lipase has been immobilized by adsorption. Various immobilization conditions as well as the properties of the immobilized lipase have been studied. The performance and the productivity of the bioreactor were evaluated as a function of the critical reaction parameters such as temperature, substrate concentration, and product inhibition. By using a 500‐mL column bioreactor, 1.8 kg of optically pure (S)‐(+)‐Naproxen were produced after 1200 h of continuous operation with a slight loss of the enzymatic activity.
Kinetic parameters of a mixed culture oxidizing sulfide and sulfur with oxygen
Authors: Buisman Cees J. N. , Jspeert Peter I , Hof Anne , Janssen Albert J. H. , Hagen Robert Ten , Lettinga Gatze 
Published: December 2004

AbstractKinetic parameters of biological sulfide oxidation are described. The influence of the sulfide loading rate on growth yield and specific oxidation rate were investigated with free‐cell suspensions. It is concluded that at least two types of bacteria were present, namely, sulfate producers (type A) that grow at higher loading rates. Type A bacteria have a growth yield of 04 g dry S/mol S, while type B bacteria have a growth yield of 04 g dry S/mol S. Type A has a high affinity for sulfide and is inhibited by sulfide at sulfide concentrations exceeding 10 mg/L. Type B has a low affinity for sulfide and is not inhibited by sulfide, but by oxygen.
Size changes associated with metal adsorption onto modified bone gelatin beads
Authors: Petersen James N. , Davison Brian H. , Scott Charles D. , Blankship Stephen L. 
Published: December 2004

AbstractSignificant quantities of heavy metals will adsorb onto modified bone gelatin beads. As this adsorption occurs, the bead can undergo a substantial volume change. Research has shown that the equilibrium bead diameter was a function of the solution pH and the ion concentration in the solution. Here, we demonstrate that under certain conditions, the volume of the beads that absorbed the metal was only 35% of the bead volume when no metal was adsorbed. By taking advantages of these size changes, a fluidized‐bed separator can be operated such that natural segregation of loaded beads occurs. This phenomenon may facilitate the design of continous separators for the recovery and concentration of heavy‐metal‐contaminated waters. These concepts are demonstrated using Cu2+ adsorption onto such beads.
Amperometric determination of amino group on a solid support using glutaraldehyde
Authors: Ukeda Hiroyuki , Nakzono Yukika , Matumoto Kiyoshi , Osajima Yutaka 
Published: December 2004

AbstractA simple amperometric method has been developed for the determination of amino groups on a solid support. The method is based on oxygen consumption during the reaction between the bifunctional reagent gluaraldehyde and the amino groups on the solid support. Oxygen consumption was monitored with a Clark oxygen electrode. AHSepharose 4B, Affi‐Gel 102, and Amino‐Celluofine were used as amino‐terminal solid supports. The concentration of amino groups on each support was calculated from a calibration curve of the standard compound. When hexamethylenediamine was used as the standard, the concentration of amino groups on AH‐Sepharose 4B and Affi‐Gel 102 by the present method showed good agreement with that by the conventional method. In the case of Amino‐Cellulofine, ethanolamine had to be selected as the standard. The relative standard deviation for six successive determinations of AH‐Sepharose 4B was 3.2%; the polymerization of glutaraldehyde showed no effect on the result. The spectral property of AH‐Sepharose 4B treated with glutataraldehyde showed no effect on the result. The spectral property of AH‐Sepharose 4B treated with lutaraldehyde suggested that the reaction mechanism of the present method was based on the oxygen consumption during the formation of the pyridinium salt on the support. A comparative study of the present method with a colorimetric method with Traut's regent is also included.
Protein immobilization to polystyrene via long poly(ethylene lycol) chains
Authors: Bergström Karin , Holmberg Krister 
Published: December 2004

AbstractHuman albumin has been attached to 24‐hole polystyrene plates via branched poly(ethylene lycol) (PEG) spacer arms. A tetraepoxude of PEG of molecular weight (1.4–1.5) × 104 g/mol was reacted with the protein in solution allowing approximately one‐third of the oxirane rings to react. The protein conjugate was then coupled to the long, cationic polymer poly(ethylene imine) (PEI), and the protein‐PEG‐PEI adduct was subsequently adsorption to unmodified polystyrene. Since the protein is linked to the surface via long, hydrophilic and nonchargedchains, interactions between the biomolecule and the surface is minimized.
Application of lipase to concentrate the docosahexaenoic acid (DHA) fraction of fish oil
Authors: Yadwad V. B. , Ward O. P. , Noronha L. C. 
Published: December 2004

AbstractA commercial lipase preparation from Rhizopus niveus was used to concentrate the omega‐3 fatty acid, docosahexaenoic acid (DHA) component in fish oil. The DHA content of cod‐liver oil was 9.64% (w/w) of total fatty acids. Enzymatic digestion conditions were established which produced a DHA content in the monoglycerides fraction of 29.17% (w/w) of total fatty acid, triglyceride, and diglyceride components were 5.72, 9.95, and 15316%, respectively.
Spectrophotometric method for high biomass concentration measurements
Authors: Thatipamala R. , Hill G. A. 
Published: December 2004

AbstractContinuous monitoring of concentration is important in the optimal control of bioreactors. Spectrophotometry provides a simple, accurate, and rapid way for measuring cell concentration of unicellular microorganisms, based on either Beer's law or calibration curves prepared using standard solutions. However, this method is limited to a low range of microbial concentrations, because Beer's law deviates significantly at high concentrations. In the present investigation, based on experimental work, a new technique is posed to monitor the concentration of microbial cells as high as 100 g DW/L. this is achieved by using a mixture of known concentration as reference, rather than the “ideal blank” with zero concentration of analyte. As a result, a new equation is developed that, although applied here only to microbial concentration, in principle can be used for monitoring the concentration of any optically sensitive material.
Biotransformation of dopamine to norlaudanosoline by Aspergillus niger
Authors: Hoover Larry K. , Moo‐Young Murray , Legge Raymond L. 
Published: December 2004

AbstractNorlaundanosoline is a key intermediate in the synthesis of the benzylisoquinoline alkaloids providing the upper isoquinoline portion of the morphinan skeleton. This study evaluates the feasibility of using Aspergillus niger as an in situ biotransformation system to produce norlaudanosoline from dopamine. A. niger was chosen because monoamine oxidase can be readily induced in this organism. Monoamine oxidase catalyzes the conversion of dopamine to 3,4‐dihydroxyphenylacetaldehyde. In the presence of dopamine, this aldehyde will then undergo a spontaneous Picket‐Spengler condensation to form norlaudanosoline. Fermentation condition to form norlaudanosoline. Fermentation conditions were optimized for the production monoamine oxidase by using a two‐stage process consisting of a growth stage and an induction stage. pH control was found to be important, and at pH 4.5 dopamine accumulation in the cells was high as was the level of monoamine oxidase. With pH control at 4.5, up to 21% of the cellular dopamine was converted to norlaudanosoline. It is proposed that with further protein engineering improvements, this system may prove suitable for the in situ bio‐transformation of dopamine to norlaudanosoline.
Mathematical model for apical growth, septation, and branching of mycelial microorganisms
Authors: Yang H. , King R. , Reichl U. , Gilles E. D. 
Published: December 2004

AbstractA mathematical model for apical growth, septation, and branching of mycelial microorganisms is presented. The model consists of two parts: the determinstic part of the model is based on fundamental cellular and physical mechanisms; it represents the kinetics for growth of hyphal tips and septation of apical as well as intercalary compartments. In regard to random occurrences of hyphal growth and branching, the stochastic part deals with branching processes, tip growth directions, and outgrowth orientations of branches. The model can explain the morphological development of mycelia up to the formation of pellets. The results, as predicted by the model, correspond very closely to those observed in experiments. In addition, some unmeasured states can be ascertained, such as the distribution functions of hyphal length (biomass) and tips along pellet radii.
Correlating the effect of pretreatment on the enzymatic hydrolysis of straw
Authors: Koullas D. P. , Christakopoulos P. , Kekos D. , Macris B. J. , Koukios E. G. 
Published: December 2004

AbstractAvicell, Alkali‐treated straw cellulose (ATSC), and wheat straw were ball‐milled to reduce crystallinity; wheat straw was delignified by hot (120°C) sodium hydroxide solutions of various concentrations. The physically and chemically pretreated cellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Enzymic hydrolysis data were fitted by the hyperbolic correlation of Holtzapple, which involves two kinetic parameters, the maximum conversion (Xmax), and the enzymic hydrolysis time corresponding to 50% of Xmax (t1/2). An empirical correlation between Xmax and cellulose crystallinity, lignin content, and degree of delignification has been found under our experimental conditions. Complete cellulose hydrolysis is shown to be possible at less than 60% crystallinity indices or less than 10% lignin content.
Effects of nonionic surfactant on enzymatic hydrolysis of used newspaper
Authors: Park Jin Won , Takahata Yasuyuki , Kajiuchi Toshio , Akehata Takashi 
Published: December 2004

AbstractEffects of five types of nonionic surfactant having a polyoxyethylene glycol (POG) group on enzymatic hydrolysis of used newspaper were studied. The surfactants examined in this work always enhanced the saccharification. The optimum surfactant concentration was 0.05% (wt/substrate wt) in the case of POG(21) sorbitane oleic ester. Among the surfactants, POG phenyl ether types showed the highest enhancement effect, for example, with two times higher conversion at 80 h than that without surfactant. Using POG nonylphenyl ether series, the effects of surfactant were considered from the point of the HLB (hydrophile–lypophile balance) value. The GFC (gel filtration chromatography) analysis of free enzyme quantity were also done to study the effect of surfactant on enzyme adsorption onto substrate. As the HLB value increased, the free enzyme quantity and the conversion both increased. It appears that surfactants help the enzyme to desorb from the binding site on the substrate surface after the completion of saccharification at that site.
Characterization of pellet morphology during submerged growth of Streptomyces tendae by image analysis
Authors: Reichl U. , King R. , Gilles E. D. 
Published: December 2004

AbstractMany filamentous bacteria and fungi tend to form pellets, or mixtures of dispersed mycelium and pellets in liquid fermentation broths. In some cases, a specific kind of morphology is required for optimum product yield. When quantitative analysis and characterization of the pellet morphology are needed, an image processing system can be used. It allows a fast and reproducible analysis of the frequency distribution of pellet size, mean pellet size, contents of pellets, or their shape. The use of such a system allows for an on‐line analysis. For a demonstration of the method, results of two fermentations of Streptomyces tendae are shown.
Alginate as immobilization material: III. Diffusional properties
Authors: Martinsen Anita , Storrø Ivar , Skjårk‐Bræk Gudmund 
Published: December 2004

AbstractThe rate of diffusion of serum albumin (MW 6.9 · 104 D) out of beads of calcium alginate gels depends upon the concentration and uronic acid composition of the alginate (ManA/GulA ratio), the conditions under which the beads are produced, the pH, and the temperature. The diffusion coefficient decreases with increasing alginate concentration, and (ManA/GulA) ratio and with decreasing pH. Diffusion out of the beads, in which the alginate is uniformly distributed (homogeneous gel), is faster than out of the beads in which the alginate is concentrated at the surface (inhomogeneous gel). The temperature dependence of the diffusion coefficient follows the Arrhenius law, with an activation energy of ∼23 kJ · mol−1.
Evaluation of production of recombinant human interleukin‐2 in fluidized bed bioreactor
Authors: Kratje Ricardo B. , Wagner Roland 
Published: December 2004

AbstractThe production of recombinant human interleukin‐2 in a fluidized bed bioreactor containing porous glass carriers is described. Cultivations were carried out with different medium formulations over 80 days. Maximal cell densities and product yield could be maintained even when protein free medium was perfused, with less than 10% cell washout. Due to this effective immobilization of the cells in the reactor, continuous operation was easy to perform. Final cell densities on the order of 3.8 × 108 mL−1 intrasphere volume were reached while the interleukin‐2 production rate was 0.75 mg L−1 d−1. The production rate showed a maximum of a 1.9 fold decrease compared with a homogeneous stirred bubble‐free aerated system. This result was in contrast to that achieved with hybridoma cell lines, where better performance was obtained with the fluidized bed bioreactor. The situation may reflect the problems caused by the dense cell culture with adherent cells, as previously shown in a hollow‐fiber bioreactor with the same cell line.
Dynamic affinity between dissociable coenzyme and immobilized enzyme in an affinity chromatographic reactor with single enzyme
Authors: Miyawaki Osato , Yano Toshimasa 
Published: December 2004

AbstractThe affinity chromatographic reactor (ACR) is a bioreactor which utilizes the dynamic interaction or the dynamic affinity between a free coenzyme and immobilized enzymes for the highly efficient regeneration of dissociable coenzymes. Dynamic affinity between free NAD and immobilized alcohol dehydrogenase (ADH) in ACR was investigated by three different methods. ADH catalyzed both oxidation and reduction of NAD, consuming propionaldehyde and ethanol. The theoretical model under consideration elucidated a criterion for the expression of the dynamic affinity as a relationship among the affinity constants and the concentrations of a coenzyme and immobilized enzyme. This criterion was confirmed experimentally by the measurements of the retention time of NAD and the half‐life period of the reactor activity after one‐shot pulse injection of NAD to ACR. In the stability measurement of the immobilized enzyme, it became clear that ADH was more stable at the higher concentration in immobilization. Although the present case of coenzyme cycling by a single enzyme is very special, with limited chance for the direct application, the results obtained here provide a theoretical basis for ACR with multienzymes–which is of more general use.
An extension of the pressure‐test technique for immobilized biocatalyst preparations
Authors: Vlaev S. D. , Valeva M. 
Published: December 2004

AbstractBased on an analysis of variables in the Ergun equation for pressure drop in granular beds, the technique of pressuretesting of immobilized biocatalyst preparations is reexamined from the point of view of evaluation of biocatalyst mechanical properties in packed bed reactors. The variation of biocatalyst particle size in the course of bioreactor performance was found to be a convenient estimate of mechanical strength for the biocatalyst particles. Based on this finding, an extension of the pressure‐test technique with particle size analysis was proposed as an opportunity to carry out differential analysis of biocatalyst structure, regardless of time and position. An example of bed destruction is given to support the suggested characterization analysis.
Characterization of the mutant lytic state in lambda expression systems
Authors: Padukone N. , Peretti S. W. , Ollis D. F. 
Published: December 2004

AbstractThe two propagative phases of bacteriophage lambda, lysogeny and lysis, can be used in concert to enhance productivity of recombinant expression systems. Lambda vectors carrying mutations to prevent both cell lysis and λ DNA packaging in the lytic state have been shown to yield 100% stability of the product gene in lysogeny and to produce up to 15% of total cell protein as product β‐galactosidase in a mutant lytic state.14 Despite these mutations, partial lysis of the culture was observed following induction of the cells from a lysogenic phase into the lytic state. To understand better the phage‐host cell interactions and to investigate the possible cause(s) of lysis in these highly productive expression systems, we have made a detailed study of the suppressor‐free system JM105(NM1070). We have found high levels of product (15% of total cell protein as β‐glactosidase) to be due chiefly to a high‐copy number of λ DNA in the mutant lytic state. There is partial lysis of the culture even in this suppressor‐free system caused by a low‐level natural suppression of the amber mutation in gene S of NM1070, resulting in accumulation of λ endolysin. We have also monitored changes in cell growth and morphology upon induction of the lysogen. There is a slight increase in cell number that follows a linear relationship with time and a 25‐fold increase in cell volume during recombinat protein production in the mutant lytic state.
Noninvasive evaluation of somatic embryogenesis
Authors: Harrell R. C. , Bieniek M. , Cantliffe D. J. 
Published: December 2004

AbstractCallus Suspension Cultures of Ipomea batates Poir. cv. White Star were grown in an airlift bioreactor. A machine vision system was used to monitor nondestructively callus growth during a 10 day culture period. Growth data obtained with this system included the overall reactor population and population estimates for the 200–1200‐μm fractions at 200‐μm intervals. A model of callus growth was developed to explain the mechanics of callus enlargement. The model was based on the assumptions that (1) the calli could not subdivide or shrink, (2) there was a fixed percentage of the initial population for each fraction that was nonviable, and (3) growth rates did not vary with time during the culture period. It was determined that the growth rates and nonviable ratios decreased as fraction size increased.