bluuebunny/crossref_metadata_2025_split huggingface dataset:
A simple Na2SO3 feeding method for KLa measurement in large‐scale fermentors
Authors: Imai Yasuhiko , Takei Hirosuke , Matsumura Masatoshi 
Published: December 2004

AbstractA simple and convenient method for measuring KLa in large‐scale fermentors was proposed. This method was based on the measurement of the dissolved oxygen concentration under steady state conditions established by an equivalency of the sulfite ion feed and chemical oxidation rates. This method had the following advantages: It was a steady state method, and so it was not necessary to consider the response lag of a dissolved oxygen probe and the response lag due to gas phase mixing in fermentors. The oxygen content of the effluent gas in this measuring system was nearly the same as that of the sparged air. Therefore, it was possible to use the oxygen partial pressure of the sparged air for the calculation of the driving force of oxygen transfer. The detailed information on the kinetics of sulfite oxidation was not necessary, because the dissolved oxygen concentration in steady state was not influenced by sulfite oxidation rates. The KLa measurement was finished in as short a period as 150 s, even in a fermentor with a volume of 10 m3. Since the amount of Na2SO4 accumulation in the test fermentors was very small because of the quick measurement, the KLa values obtained by this method were applicable to the electrolyte‐free system. Furthermore, we could discharge the used liquid from the fermentors into a drain without any pretreatment due to the low salt concentration.
Matrix method for determining steps most rate‐limiting to metabolic fluxes in biotechnological processes
Authors: Westerhoff Hans V. , Kell Douglas B. 
Published: December 2004

AbstractThe metabolic control theory developed by Kacser, Burns, Heinrich, and Rapoport is briefly outlined, extended, and transformed so as optimally to address some biotechnological questions. The extensions include (i) a new theorem that relates the control of metabolite concentrations by enzyme activities to flux ratios at branches in metabolic pathways; (ii) a new theorem that does the same for the control of the distribution of the flux over two branches; (iii) a method that expresses these controls into properties (the so‐called elasticity coefficients) of the enzymes in the pathway; and (iv) a theorem that relates the effects of changes in metabolite concentrations on reaction rates to the effects of changes in enzyme properties on the same rates. Matrix equations relating the flux control and concentration control coefficients to the elasticity coefficients of enzymes in simple linear and branched pathways incorporating feedback are given, together with their general solutions and a numerical example. These equations allow one to develop rigorous criteria by which to decide the optimal strategy for the improvement of a microbial process. We show how this could be used in deciding which property of which enzyme should be changed in order to obtain the maximal concentration of a metabolite or the maximal metabolic flux.
Forced‐flow electrophoresis of proteins and viruses
Authors: Mullon C. , Mason N. , Sparks R. 
Published: December 2004

AbstractThis article describes a model for forced‐flow electrophoresis (FFE), considering the desired species fraction removal, other fraction removals, and outlet concentrations of all species in the system. The model predicts the necessary inlet flow rate of the retentate chamber and the rate of filtration and the voltage gradient and also provides an appropriate heat balance permitting consideration of possible heat denaturation of the species. The equipment consists of two membranes and a filter, the electric field being imposed by means of external electrodes, and two fractions are obtainable. The main discriminating factor is not the pore sizes of the filter but the relative solute ionization, which depends on the pH and the ionic strength of the buffer solution. Serum proteins (albumin, γ‐globulin) and bacteriophages (M13, MS2, ϕX174) have been used to characterize the separation process.
A comparison of some methods of estimating volumetric mass‐transfer coefficients in an external‐loop airlift fermenter
Authors: Kamp F. , Wase D. A. J. , McManamey W. J. , Mendoza O. , Thayanithy K. 
Published: December 2004

AbstractVolumetric mass‐transfer coefficients were measured in an 11‐L external‐loop airlift fermenter with deionized water, a fermentation medium, and during a fermentation. Both a Mackareth oxygen electrode and a novel rapid‐response probe were used. When the conventional step‐change dynamic method was used for water, the long, nonlinear response time of the Mackareth electrode made correction of its readings difficult; this problem did not occur when the rapid‐response probe was used. A comparison was made with a method of mass‐transfer coefficient determination which does not involve any assumptions about the gas residence time distribution. However, this method requires that the liquid phase is well‐mixed and this requirement was not met in the airlift fermenter. Comparison of the present results with other KL a determinations for airlift fermenters showed that KL a in water depends on the active gas holdup, the value of KL a/ϵ at 20°C being ca. 0.37 s−1. Although higher gas holdups were obtained with the fermentation medium than for water, the values of KL a/ϵ were lower, ca. 0.22 s−1 at 20°C.
Co‐operative binding interactions in affinity chromatography: Theoretical considerations
Authors: Hubble John 
Published: December 2004

AbstractA theoretical relationship has been developed to allow the effect of free ligand concentration on the capacity of an affinity Chromatography matrix to be determined where the protein adsorbed shows co‐operative binding. Computer simulations using literature values for association constants show that under optimal conditions resin capacity can be increased significantly in the presence of a small but finite concentration of free ligand. The model also allows prediction of the soluble ligand concentration required for biospecific elution. The results obtained suggest the possibility of a new elution technique, “reverse biospecific elution,” that reduces the amount of free ligand required to effect elution.
Immobilized heparinase: In vitro reactor model
Authors: Bernstein Howard , Yang Victor C. , Langer Robert 
Published: December 2004

AbstractHeparinase immobilized to agarose has previously been shown to be useful in degrading heparin and thereby preventing thromboembolytic complications when this anticoagulant has been used in extracorporeal perfusions. The current study examined the kinetics of this immobilized enzyme. When heparinase is covalently bound to 8% agarose, the partition coefficient of heparin in the catalytic particle is 0.36 ± 0.048 (N = 10). The immobilized enzyme has a Km of 0.15 ± 0.03 mg/mL and an activation energy of 10.3 ± 0.57 kcal/gmol (N = 5). These values are statistically indistinguishable from the values for the free enzyme. The immobilized enzyme showed a pH activity optimum between 7.0 and 7.4, compared to the optimum pH of 6.5 for the soluble enzyme. The activity optimum of immobilized heparinase with respect to salt concentration was between 0 and 0.1M. A reactor containing immobilized heparinase recirculating internally at 1300 mL/min behaved as a continuously stirred tank reactor (CSTR) when solutions at a flow rate of 120 mL/min were passed through the device. The residence time distribution was determined using blue dextran (molecular weight 2 × 106 daltons), which is sterically excluded from the agarose catalyst. A model of the heparinase reactor based on ideal CSTR behavior and the immobilized enzyme kinetic parameters was developed. It accurately predicted experimental conversions over a range of catalyst volumes, enzyme loadings, and substrate concentrations to within 7% in most cases and with a maximum deviation of 13%.
Stratified ecology techniques in the startup of an anaerobic downflow fixed film percolating reactor
Authors: Canovas‐Diaz M. , Howell J. A. 
Published: December 2004

AbstractA two‐column pilot scale downflow percolating fixed film (DPFF) anaerobic reactor treating deproteinized cheese whey (DPW) was used in this study. The system was operated at one‐third of the maximum working volume in an attempt to avoid mass transfer limitations of the gas products (since two‐thirds of the immobilized microbial culture was unsubmerged), as well as to minimize the effects of localized high volatile fatty acids (VFA) levels and low pH on its methanogenic activity. A new method to shorten the start‐up period was used by growing methanogenic and acetogenic (H2‐producers) bacteria on a synthetic medium until reaching a stable methane production rate and then switching the reactor over to DPW and allowing acidogenic growth. The start‐up period was reduced to 35 days as a result of this operational mode. The reactor was able to handle 8 kg COD/ m3·d after 35 days of operation.
Catabolite repression of amylase synthesis in yeast
Authors: Pasari Ajay B. , Korus Roger A. , Williams Ronald A. , Heimsch Richard C. 
Published: December 2004

AbstractAmylase synthesis by the yeasts Saccharomycopsis fibuligera and Schwanniomyces castellii and alluvius is repressed by glucose. Steady state continuous culture data for amylase activity, E, biomass concentration, X, and reducing sugar concentration, S, were fitted to the three‐parameter catabolite repression model

and biomass productivity, DX, and amylase productivity, DE, were determined for S. castellii and S. alluvius.
A mathematical model for prediction of plasmid copy number and genetic stability in Escherichia coli
Authors: Ataai M. M. , Shuler M. L. 
Published: December 2004

AbstractThe design of bioreactors for genetically modified bacterial cultures would benefit from predictive models. Of particular importance is the interaction of the external environment, cell physiology, and control of plasmid copy number. We have recently developed a model based on the molecular mechanisms for control of replication of Co1E1 type plasmids. The inclusion of the plasmid model into a single‐cell E. coli model allows the explicit prediction of the interaction of cell physiology and plasmid‐encoded functions. The model predictions of the copy number of plasmids with the Co1E1 origin of replication carrying a variety of regulatory mutations is very close to that observed experimentally.All of the model parameters for plasmid replication control can be obtained independently and no adjustable parameters are needed for the plasmid model. In this article we discuss the model's use in predicting the effect of operating conditions on production of a protein from a plasmid encoded gene and the stability of the recombinant cells in a continuous culture.
Dynamics of a biological fixed film for phenol degradation in a fluidized‐bed bioreactor
Authors: Worden Robert Mark , Donaldson Terrence L. 
Published: December 2004

AbstractExperimental and modeling studies were conducted to analyze the dynamic response behavior of a phenol‐oxidizing fixed film using a differential, fluidized‐bed bioreactor in a recycle loop with a well‐mixed reservoir. With the bioreactor at steady state, a pulse of phenol was added to perturb the system, and the phenol concentration was monitored continuously until steady state was again achieved.The experimental dynamics were compared with a dynamic mathematical model based on diffusion and reaction within the biofilm, liquid mixing, and biofilm growth. Constant‐pH experiments could be adequately described using an unstructured, double‐Monod kinetic expression with substrate inhibition by phenol.However, in dynamic experiments without pH control, the pH of the liquid phase dropped, and damped oscillations were observed in the phenol concentration and reaction rate trajectories. Oscillatory solutions could not be induced in the model, even when product inhibition was included, and a linear stability analysis did not reveal tendencies toward instability. The cause of the experimental oscillations remains unknown.
Vanadium containing bromoperoxidase: An example of an oxidoreductase with high operational stability in aqueous and organic media
Authors: de Boer E. , Plat H. , Tromp M. G. M. , Wever R. , Franssen M. C. R. , van der Plas H. C. , Meijer E. M. , Schoemaker H. E. 
Published: December 2004

AbstractThe conversion is described of phenolsulphonephtalein (phenol red) to 3,3′,5,5′‐tetrabromophenolsulphonephthalein (bromophenol blue) by bromoper‐oxidase from the brown alga Ascophyllum nodosum. This reaction provides a convenient assay for the detection of bromoperoxidase activity in vitro. Bromoperoxidase was shown to be stable under turnover conditions for three weeks at room temperature, catalyzing the bromination of phenol red into bromophenol blue. When stored at room temperature in organic sol vents such as acetone, methanol, ethanol [present up to 60% (v/v)], and 1‐propanol [40% (v/v)], bromoperoxidase was stable for more than one month. As far as we know this is the first example of an oxidoreductase which displays such great stability. This enhances the applicability of the enzyme in organic synthesis.
Characteristics of immobilized yeast reactors producing ethanol from glucose
Authors: Anselme M. J. , Tedder D. W. 
Published: December 2004

AbstractThe evolutionary performance of up flow reactors are affected by the cell immobilization matrix and the matrix particle size distribution. Higher productivities are obtained using a low‐density brick with a particle size of ca. 400–1400 μm. A medium condition favoring growth quickly leads to large biomass gradients within the reactors and, eventually, reductions in average productivities due to bed plugging. These systems can be accurately modelled using Monod kinetics when dispersion and the biomass gradient are considered. The productivity was apparently not controlled by substrate diffusion in these cases.
Potential enhancement of photosynthetic energy conversion in algal mass culture
Authors: Sukenik A. , Falkowski P. G. , Bennett J. 
Published: December 2004

AbstractActual laboratory data obtained from steady‐state Dunaliella tertiolecta cultures grown under a wide range of photon flux densities were used in a simple model to calculate daily production in a conventional algal mass culture system. In spite of large physiological and biochemical variations between low‐light‐ (LL) and high light‐ (HL) adapted cultures, the overall calculated daily productivity is almost identical for both strains grown at optimal conditions. When production of fine biochemicals is considered, however, a hypothetical HL strain, which cannot shade adapt, is advantageous. Based on biochemical and biophysical analysis of D. tertiolecta responses to growth irradiance levels, specific targets are defined for genetic manipulation to enhance productivity in algal mass culture systems. The targets identified are (1) amplification of the carboxylation enzyme ribulose‐1,5‐bisphosphate carboxylase‐oxygenase relative to the electron transport complexes, which should increase photosynthetic capacity at light saturation, and (2) enlargement of the light‐harvesting complexes by varying their pigment composition in order to increase light harvesting at low photon flux densities.
Formation of oligosaccharides during enzymatic lactose hydrolysis and their importance in a whey hydrolysis process: Part II: Experimental
Authors: Prenosil J. E. , Stuker E. , Bourne J. R. 
Published: December 2004

AbstractEnzymatic lactose hydrolysis using two yeast and two fungal lactases that are of current technical interest was studied. The enzymes were compared regarding their oligosaccharide production. Parameters influencing oligosaccharide formation, together with the effect of immobilization were examined and conditions minimizing oligosaccharide content in the hydrolysis product were proposed. Enzymatic whey hydrolysis was also considered. A possibility of enzymatic lactose recombination from its hydrolysis products was shown.
Recovery of penicillin by reactive extraction in centrifugal extractors
Authors: Likidis Z. , Schügerl K. 
Published: December 2004

AbstractPenicillin V and/or G were extracted from fermentation broth by Amberlite LA‐2 in n‐butylacetate at pH 5 in a laboratory centrifugal extractor, Type SA 01 of Westfalia, up to an overall phase throughput rate of 30 L/h, in a bench‐scale four‐stage extraction system, consisting of Type TA 1 of Westfalia, up to an overall phase throughput rate of 110 L/h, and in a pilot‐plant three‐stage extraction unit, consisting of Type TA 7 extractors of Westfalia, up to a phase throughput rate of 990 L/h with very high degrees of extraction (up to 99%). The reextraction from the ion‐pair complex, which contained organic solvent, was performed by phosphate, borate, or carbonate buffer at pH 7.5–8.5 in all three extractor systems with degrees of extraction up to 98%, but at considerably lower overall phase throughput rates than those of the extraction, since no satisfactory phase separation is possible at higher throughput rates.
Alum flocculation and bioflocculation of activated sludge for vacuum filtration
Authors: Novak Richard A. 
Published: December 2004

AbstractThis study investigated the relationship between sludge loading rate, COD‐to‐nitrogen ratio of influent waste, and maximum difference in specific resistance as a result of chemical conditioning (ΔZ). It also related ΔZ to sludge carbohydrate content, protein content, and surface charge. This research also explored the necessity of chemical conditioning when an activated sludge exhibits excellent bioflocculation characteristics.
Bioflocculation as a microbial response to substrate limitations
Authors: Logan Bruce E. , Hunt James R. 
Published: December 2004

AbstractPrevious theories of nutrient supply to microbial floes assumed that transport within the flocs was by molecular diffusion, and they predict that overall nutrient uptake is reduced in floes compared to dispersed cells. Calculations, supported by recent advances in understanding fluid flow through suspended aggregates, however, have shown that substantial fluid flow may occur through highly permeable bacterial floes. Since bioflocculation of microorganisms in bioreactors is known to occur under conditions of low substrate availability, the rate of substrate uptake is assumed to be mass transfer limited. The hydrodynamic environment of a cell then determines cellular uptake rates. Through development of a relative uptake factor, the overall uptake by cells in flocs in sheared fluids and floes attached to bubbles are compared with the uptake by an identical quantity of dispersed cells. Bioflocculation is found to increase the rate of substrate transport to cells in permeable floes compared to dispersed cells, particularly for large‐molecular‐weight substrates and when bubbles are present.
Kinetics and regulation of β‐lactamase formation in methylotrophic bacterium
Authors: Samuelov Nissim S. 
Published: December 2004

AbstractThe regulation and kinetics of formation of an inducible, cell‐bound oxacillin‐hydrolyzing β‐lactamase (M‐OXA) by a methanol‐grown Pseudomonas strain were investigated in batch, chemostat, and two‐stage continuous cultures. The extent to which enzyme production occurs declines at increased growth rates, and the rate of M‐OXA β‐lactamase production follows a kinetic pattern that is partially growth independent and partially inversely growth linked. Growth and enzyme formation are regulated differently by medium constituents. The initial steps of M‐OXA β‐lactamase synthesis takes place during the exponential growth phase, and active enzyme is produced by induced nonproliferating cells, probably through a turnover mechanism.
Mathematical modeling for mixed culture growth of two bacterial populations with opposite substrate preferences
Authors: Kim Sun U. , Kim Daniel C. , Dhurjati Prasad 
Published: December 2004

AbstractAn unstructured mathematical model is proposed for mixed culture growth of two different bacterial species that exhibit “opposite” substrate preferences in response to the “same” environmental conditions. The model incorporates enzymatic control mechanisms such as induction, repression, and inhibition in the microorganisms as manifested in their preferential utilization of substrates and microbial interactions such as amensalism and competition. The model predicts cell mass, substrate concentrations, dissolved oxygen tension, as well as key enzyme levels. The predictions of the model are compared with experimental data for pure culture growth and for mixed culture growth on two substrates, glucose and citrate, in a batch reactor.
High‐Density culture of mouse–human hybridoma in serum‐free defined medium
Authors: Takazawa Yoshiharu , Tokashiki Michiyuki , Murakami Hiroki , Yamada Koji , Omura Hirohisa 
Published: December 2004

AbstractMouse–human hybridoma 4H11 cells producing anti‐Pseudomonas sp. monoclonal antibody (IgA) grew in a serum‐free medium supplemented with insulin, transferrin, ethanolamine, and selenite (ITES). The hybridoma could be applied to high‐density culture in a serum‐free medium supplemented with ITES, 0.5% BSA, egg yolk VLDL, and artificial blood FC‐43 in a culture vessel equipped with hollow‐fiber modules for medium exchange. Total cell density reached 1.1 × 107 cells/mL (viable cell density was 7.6 × 106 cells/mL), and the IgA productivity was around 20 μg/106 cells/day in the serum‐free medium, which corresponded to the levels in serum‐supplemented medium.
Fed‐batch fermentation for the production of α‐amylase by Bacillus amyloliquefaciens
Authors: Yoo Young J. , Cadman Theodore W. , Hong Juan , Hatch Randolph T. 
Published: December 2004

AbstractFed‐batch cultures were performed to maximize the α‐amylase activity in a bioreactor. Kinetic equations containing a catabolite repression effect were used to model the enzyme formation from Bacillus amyloliquefaciens. Fed‐batch culture experiments were performed using maltose to implement the optimal feeding strategy. Optimal fed‐batch culture based on sequential parameter estimation was performed successfully using off‐line analysis while the fermentation was in progress. The enzyme activity from the fed‐batch culture employing maltose was higher than that of the batch culture by 60%. Enzyme production using starch showed similar trends to those obtained using maltose.
Influence of the water activity of a solid substrate on the growth rate and sporogenesis of filamentous fungi
Authors: Gervats P. , Molin P. , Grajek W. , Bensoussan M. 
Published: December 2004

AbstractThe water activity (aw) of substrates has been related to the mycelial growth and the sporogenesis of two molds. In the absence of other limiting factors, optimal aw values were determined for growth and sporogenesis as 0.99 and 0.98, respectively, for Trichoderma viride TS and 0.97 and 0.96 for Penicillium roqueforti. In all cases, the accuracy of the optimal value would justify the regulation of this parameter. A model was proposed which establishes a relationship between the mycelial growth and the water activity value of the substrate.