bluuebunny/crossref_metadata_2025_split huggingface dataset:
Economic evaluation of preconcentration in production of ethanol from dilute sugar solutions
Authors: Zacchi G. , Axelsson A. 
Published: December 2004

AbstractThe economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated. Two methods, evaporation and reverse osmosis, are compared. A computer program to determine the optimal preconcentration conditions for glucose solutions of 1.5–16 wt% has been developed. It was used to compute the fractional cost for labor and maintenance, preconcentration, fermentation, and distillation. Preconcentration with evaporation resulted in a higher total cost, compared with no preconcentration, for all cases studied, although a six‐effect unit was used. Reverse osmosis was found to be economically feasible for preconcentration to about 5–10 wt % depending on the concentration of the feed.
Bioactive polymers. 56: Urease immobilization on carboxymethylcellulose
Authors: Dumitriu Severian , Popa Marcel , Artenie Vlad , Dan Florin 
Published: December 2004

AbstractThis article reports on the reaction of urease immobilization through its covalent bonding on carboxymethylcellulose. The reaction is activated by dicyclohexylcarbodiimide. The coupling reaction is influenced by the enzyme–support and activator–support ratios, as well as by duration. Starting from a rotating, composed experimental program of the second order, the function correlating the activity of the immobilized enzyme with the reaction parameters is established. Immobilized urease exhibits thermal stability higher than that of free enzyme, regarding both pH and the inhibiting action of some metal ions or organic substances. The stability over time of the immobilized urease is high, its enzymatic activity being maintained at over 85% of the initial value three months after synthesis.
Theoretical analysis of G6P production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow‐fiber reactor
Authors: Ishikawa Haruo , Tanaka Takenori , Takase Susumu , Hikita Haruo 
Published: December 2004

AbstractThe performance of an ultrafiltration hollow‐fiber reactor, in which the enzymatic synthesis of glucose 6‐phosphate from glucose and cofactor ATP and the enzymatic regeneration of ATP from ADP and acetyl phosphate are performed simultaneously, was analyzed theoretically. A simple analytical model in which the liquid flowing in the fiber tubes is assumed to be plug flow, and the radial concentration gradients in the tube and shell sides are both neglected, could simulate the reactor performance with satisfactory accuracy. The simulation elucidated the effects of the reactor configurations and various operational conditions on glucose conversion, ATP recycle number, and space–time yield. If the fiber tubes, through which the permeability of the relevant components such as substrates is high, were packed as much as possible in the reactor, good reactor performance could be expected. Furthermore, with a sufficiently high enzyme concentration, low ATP concentration in the feed solution, and appropriate space velocity, good space–time yield with high glucose conversion and with very high ATP recycle number is theoretically possible.
Continuous production of 3‐fluoro‐L‐alanine with alanine dehydrogenase
Authors: Ohshima Toshihisa , Wandrey Christian , Conrad Dietrich 
Published: December 2004

AbstractAlanine dehydrogenase catalyzed the conversion of 3‐fluoropyruvate into 3‐fluoro‐L‐alanine in the presence of NADH and ammonia. The optimum pH of the reaction was 7.8. The Km values of the enzyme for 3‐fluoropyruvate, polyethylene glycol‐bound NADH, and ammonia were 2.94, 0.56, and 105mM, respectively. 3‐Fluoro‐L‐alanine was selectively and continuously produced from 3‐fluoropyruvate and ammonium formate in an enzyme membrane reactor by the multienzyme reaction system of alanine dehydrogenase and formate dehydrogenase with a simultaneous coenzyme regeneration. The average conversion and the space–time yield were 73% and 75 g/L day, respectively, with operation of the reactor for 4 days. Alanine dehydrogenase and formate dehydrogenase consumed were 11, 370 and 22, 950 units/kg 3‐fluoro‐L‐alanine, respectively. The cycle number was 3150 mol/mol NAD.
Esterification‐coupled extraction of organic acids: Partition enhancement and underlying reaction and distribution equilibria
Authors: Aires‐Barros M. R. , Cabral J. M. S. , Willson R. C. , Hamel J.‐F. P. , Cooney C. L. 
Published: December 2004

AbstractA novel means of extracting carboxylic acids from aqueous solutions is described which involves the use of a lipolytic enzyme to convert the acid to a more hydrophobic ester. A water‐immiscible long‐chain alcohol serves both as a reactant in esterifying the acid, and as a solvent for extraction of the ester. Radiochemical tracer studies of the underlying reaction and extraction equilibria established that a low equilibrium concentration of ester (0.04–0.5mM) in the presence of water is counterbalanced by the high distribution coefficient of the ester (220–3380, wt. basis). The net result is a substantial (4‐ to 15‐fold) increase in the apparent distribution coefficient of the acid; 80%–95% of the extracted acid is in the esterified form. The method is applicable to a variety of alcohols and acids.
Integral kinetics of α‐galactosidase purified from Glycine max for simultaneous hydrolysis of stachyose and raffinose
Authors: Porter Jill E. , Herrmann Klaus M. , Ladisch Michael R. 
Published: December 2004

Abstractα‐Galactosidase from soybean (Glycine max) was purified by a five‐step procedure. The enzyme's natural substrates, raffinose and stachyose, have Km's of 3. 0 mM and 4. 79 mM, respectively. The products, galactose and sucrose, were measured after separation by liquid chromatography. Galactose is a competitive product inhibitor of stachyose and raffinose hydrolysis with a Ki of 0. 12 mM. We determined these parameters by an integral kinetic approach. Stachyose hydrolysis gives a nearly constant level of raffinose shortly after hydrolysis begins. Thus, cleavage of the first α‐(1,6)‐bond in the tetrasaccharide is the rate‐limiting step. Since the stachyose hydrolysis yields raffinose, soybean α‐galactosidase simultaneously hydrolyzes two substrates. We present a novel approach for analyzing simultaneous substrate hydrolysis with competitive product inhibition by a modified integral rate expression. The experimentally found kinetic parameters are confirmed by solving the simultaneous equations which describe the hydrolysis. This technique may be applicable to other hydrolytic enzymes with multiple substrates.
Morphological measurements on filamentous microorganisms by fully automatic image analysis
Authors: Packer H. L. , Thomas C. R. 
Published: December 2004

AbstractCharacterization of mycelial morphology is important for physiological and engineering studies of filamentous fermentations, and in the design and operation of such fermentations. Image analysis has been developed as a method for this characterization, and has been shown to be faster and generally more accurate than previous methods. A fully automatic system has been developed, in which speed is gained, but with loss of accuracy in some cases. The method has been tested on Streptomyces clavuligerus and Penicillium chrysogenum P1 batch fermentations. It has also been tested on a fed‐batch Penicillium chrysogenum P2 fermentation, in which the medium contained solid ingredients. Fully automatic image analysis for morphological characterization of filamentous microorganisms is an important development which will make practical many engineering and physiological studies of such fermentations that have so far not been completely satisfactory.
Pellet formation and cellular aggregation in Streptomyces tendae
Authors: Vecht‐Lifshitz S. E. , Magdassi S. , Braun S. 
Published: December 2004

AbstractIn submerged cultures, Streptomyces tendae tended to form fluffy spherical pellets of the noncoagulative type. An increase in the average pellet size could be attained by decreasing any of the following: shear rate, pH, temperature, or inoculum size. Conditions leading to oxygen limitation tended to reduce the average pellet size and induced pulpy growth, whereas oxygen sufficiency seemed to induce pellet formation. Factors inducing pellet formation simultaneously increased cell wall hydrophobicity. It is therefore proposed that the main forces inducing cellular aggregation in S. tendae are hydrophobic interactions of cell walls, and these interactions are controlled by availability of dissolved oxygen.
Effects of stirring and sparging on cultured hybridoma cells
Authors: Gardner A. R. , Gainer J. L. , Kirwan D. J. 
Published: December 2004

AbstractThe response of hybridoma cells to fluid shear caused by stirring and sparging has been investigated in a 2‐L turbine‐agitated bioreactor. Viable cell count, lactate dehydrogenase (LDH) release, and antibody secretion were measured over the course of batch culture experiments under varied conditions of stirring and gas sparging. The effectiveness of Pluronic F68 as a protective agent in sparged cultures was also studied. Growth was found to be unaffected by stirring of the culture under surface aerated conditions, but gas sparging had a significant detrimental effect on growth and antibody production. The effect of sparging was reduced when cultures were supplemented with Pluronic at a level of 0.4% (w/v). Experimental data were analyzed through formulation of models for LDH release and antibody production. Rates of cell lysis could be estimated by correlating extracellular LDH levels through the model for LDH release. The lysis rate estimated for sparged conditions was sufficiently large to approximately account for the observed decrease in the specific growth rate of the culture. The presence of Pluronic apparently interfered with the LDH release mechanism, so precise estimation of lysis rates under these conditions was not possible. Sparging was found not to have a detrimental effect on antibody production in cultures without Pluronic added. Specific antibody production rates in cultures supplemented with Pluronic were about 25% higher than in sparged cultures without Pluronic added.
Oxygen and carbon dioxide mass transfer and the aerobic, autotrophic cultivation of moderate and extreme thermophiles: A case study related to the microbial desulfurization of coal
Authors: Boogerd F. C. , Bos P. , Kuenen J. G. , Heijnen J. J. , van der Lans R. G. J. M. 
Published: December 2004

AbstractMass transfers of O2, CO2, and water vapor are among the key processes in the aerobic, autotrophic cultivation of moderate and extreme thermophiles. The dynamics and kinetics of these processes are, in addition to the obvious microbial kinetics, of crucial importance for the industrial desulfurization of high‐pyritic coal by such thermophiles. To evaluate the role of the temperature on the gas mass transfer, kLa measurements have been used to supplement the existing published data. Oxygen mass transfer from gas (air) to liquid (5 mM H2SO4 in water) phase as a function of the temperature has been studied in a laboratory‐scale fermentor. At 15, 30, 45, and 70°C, (kLa)o values (for oxygen) were determined under three different energy input conditions by the dynamic gassing in/out method. The (kLa)o was shown to increase under these conditions with increasing temperature, and straight lines were obtained when the logarithm of (kLa)o was plotted against the temperature. By multiplying the equilibrium concentration of O2 in water with (kLa)o maximal, O2 transfer capacities were calculated. It appeared that in finite of a decreased solubility of O2 at elevated temperature in mechanically mixed fermentors the calculated transfer capacities showed only minor changes for the range between 15 and 70°C. However, in an air‐mixed fermentor the transfer capacity of O2 decreased slowly but steadily.Carbon dioxide mass transfer was predicted by calculations on the basis of the data for oxygen transfer. The maximal CO2 transfer capacity, calculated as the product of the equilibrium CO2 concentration times (kLa)c, decreased slowly as the temperature increased over the range 15–70°C under all three energy input conditions. Subsequent process design calculations showed that for aerobic, autotrophic cultures, CO2 limitation is more likely to occur than O2 limitation.
Formation of CC bonds by mandelonitrile lyase in organic solvents
Authors: Wehtje Ernst , Adlercreutz Patrick , Mattiasson Bo 
Published: December 2004

AbstractMandelonitrile lyase (EC 4.1.2.10) catalyzes the formation of D‐mandelonitrile from HCN and benzaldehyde. Mandelonitrile lyase was immobilized by adsorption to support materials, for example, Celite. The enzyme preparations were used in diisopropyl ether for production of D‐mandelonitrile. In order to obtain optically pure D‐mandelonitrile it was necessary to use reaction conditions which favor the enzymatic reaction and suppress the competing spontaneous reaction, which yields a racemic mixture of D, L‐mandelonitrile. The effects of substrate concentrations, water content, and support materials on both the spontaneous and enzymatic reactions were studied. The enzymatic reaction was carried out under conditions where the importance of the spontaneous reaction was negligible and high enantiomeric purity of D‐mandelonitrile was achieved (at least 98% enantiomeric excess). The operational stability of the enzyme preparations was studied in batch as well as in continuous systems. It was vital to control the water content in the system to maintain an active preparation. In a packed bed reactor the enzyme preparations were shown to be active and stable. The reactors were run for 50 h with only a small decrease in product yield.
Kinetics of CO2 hydration in fermentors: pH and pressure effects
Authors: Yegneswaran P. K. , Gray M. R. , Thompson B. G. 
Published: December 2004

AbstractFluctuations in pH and head‐space pressure in a fermentor introduce temporary changes in off‐gas CO2 concentrations. These changes are quantified using a simple model based on kinetics of CO2 hydration and gas–liquid mass transfer. The model is verified experimentally. An eigenvalue analysis of the model indicates that mass transfer is the parameter which controls the dynamics of CO2 equilibration.
A comparison of mathematical model predictions to experimental measurements for growth and recombinant protein production in induced cultures of Escherichia coli
Authors: Betenbaugh Michael J. , Dhurjati Prasad 
Published: December 2004

AbstractRecombinant cell growth and protein synthesis by a recombinant Escherichia coli under various inducing conditions are compared to the predictions of a mathematical model. The mathematical model used was a combination of two literature models: (1) an empirical kinetic model for recombinant growth and product formation and (2) a genetically structured model of the lac promoter‐operator on a multicopy plasmid. The experimental system utilized was recombinant E. coli CSH22 bearing the temperature‐sensitive plasmid pVH106/172, which codes for the synthesis of β‐galactosidase and the other lac operon genes under the control of a lac promoter. Mathematical model predictions for recombinant β‐galactosidase yield and specific growth rate were compared with fermentation measurements of these same quantities for conditions of chemical induction with cyclic AMP and IPTG, copy number amplification (by shifting culture temperature), and combined chemical induction and copy number amplification. The model successfully predicted experimental product yields for most cases of chemical induction even though the product yields varied from 0.34 × 103 to 1500 × 103 units/g cell mass. The kinetic model also correctly predicted a decline in the specific growth rate with increasing levels of plasmid and recombinant protein. The model was less successful at predicting product amplification at high copy numbers. A comparison of model predictions and experimental results was also used to investigate some of the assumptions used in constructing the mathematical models.
Countercurrent multistage fluidized bed reactor for immobilized biocatalysts: I. Modeling and simulation
Authors: Vos Henk J. , Groen Dick J. , Potters Jacques J. M. , Luyben Karel Ch. A. M. 
Published: December 2004

AbstractFor the application of immobilized enzymes, fixed bed reactors are used almost exclusively. Fixed bed reactors have specific disadvantages, especially for processes with a deactivating catalyst. Therefore, we have studied a novel reactor type with continuous transport of the immobilized biocatalyst. Flow of biocatalyst is countercurrent to the substrate solution. Because of a stagewise reactor design, back‐mixing of biocatalyst is very limited and transport is nearly plug flow. The reactor operates at a constant flow rate and conversion, due to constant holdup of catalytic activity. The reactor performance is compared with a configuration of fixed bed reactors. For reactions in the first‐order regime, enzyme requirements in this new reactor are slightly less than for fixed bed processes. The multistage fluidized bed appears to be an attractive reactor design to use biocatalyst to a low residual activity. However, nonuniformity of the particles might affect plug flow transport of the biocatalyst. A laboratory scale reactor and experiments are described in Part II1 of this series. Hydrodynamic design aspects of a multistage fluidized bed are discussed in more detail in Part III.2
Mechanisms for biopolymer accumulation in immobilized Acinetobacter calcoaceticus system
Authors: Wang Sy‐Dar , Wang Daniel I. C. 
Published: December 2004

AbstractThe gram‐positive bacteria, Acinetobacter calcoaceticus, is capable of accumulating biopolymer in the carrier matrix of an immobilized cell system. Several possible mechanisms for the biopolymer accumulation are evaluated. It appears that direct solid surface polymer adsorption and polymer diffusion limitation within the pore space are minor factors in biopolymer accumulation. Calculations demonstrate that the cell bound polymer to dry cell weight ratio is much higher for immobilized cells than for free cells. The higher cell‐bound polymer to dry‐cell‐weight ratio for immobilized cells as well as the accumulation of the immobilized cells in the Celite matrix are believed to be the main factors for biopolymer accumulation in the Carrier matrix. Further studies reveal that the cell‐bound polymer to dry‐cell‐weight ratio is strongly affected by shear forces. At zero shear stress, such as would be present in the carrier matrix, cell bound polymer to dry cell weight ratio can be as high as 1.6. As the shear stress increases, this ratio decreases. When shear stress increases above 5 dyn/cm2, a level equivalent to the shear experienced by free cells in a stirred tank fermentation, cell‐bound polymer decreases to less than 20% of dry cell weight. A macroscopic model is developed to describe the effect of shear stress on the cell‐bound polymer to dry‐cell‐weight ratio.
A new biosensor for specific determination of glucose or fructose using an oxidoreductase of Zymomonas mobilis
Authors: Park Je‐Kyun , Kim Hak‐Sung 
Published: December 2004

AbstractCells of Zymomonas mobilis were permeabilized with toluene in order to utilize the enzymes, glucose–fructose oxidoreductase and gluconolactonase, inside the intact cells. Permeabilized cells were immobilized in a gelatin membrane, and a whole cell enzyme electrode was constructed by fixing the membrane on pH electrode. The biosensor developed was used for specific determination of glucose or fructose by detecting the production rate of hydrogen ion. Optimum conditions for biosensor response were pH 6.2 and temperature of 39 °C. The biosensor was highly specific and reproducible, and calibration curves for glucose and fructose were excellent, being linear up to 5 and 50 g/L, respectively.
A balanced DO‐stat and its application to the control of acetic acid excretion by recombinant Escherichia coli
Authors: Konstantinov Konstantin , Kishimoto Michimasa , Seki Tatsuji , Yoshida Toshiomi 
Published: December 2004

AbstractDuring fed‐batch cultivation of a recombinant Escherichia coli AT2471 harboring plasmid pSY130–14 for phenylalanine production, a large amount of acetic acid was excreted by the cells and accumulated in the culture medium. Acetic acid concentration reached 30–35 g/L at the end of a process conducted without special precautions for the reduction of this excretion. Cell growth stopped when acetic acid concentration was about 15 g/L, resulting in poor growth, 16 g/L cell concentration, and poor production — 8 g/L phenylalanine. A novel control strategy, called a balanced DO‐stat. was developed to prevent acetic acid excretion. It represents a model‐independent two‐loop control structure, which is simple, reliable, and convenient for computer application. Using the balanced DO‐stat, implemented in a computer control system, acetic acid concentration was kept at zero during the entire cultivation period. As a result, the cell concentration increased to 36 g/L and phenylalanine concentration reached 24 g/L. Aside from the phenylalanine fermentation, the proposed control approach might be applied to cultivation of other bacterial and yeast strains which have similar mechanism of the excretion of fermentative by‐products.
Foam fractionation of globular proteins
Authors: Brown Lynn , Narsimhan Ganesan , Wankat P. C. 
Published: December 2004

AbstractFoam fractionation of bovine serum albumin (BSA) was studied as a model system for potato wastewater. The effects of feed concentration, superficial gas velocity, feed flow rate, bubble size, pH, and ionic strength on the enrichment and recovery of BSA were investigated in a single‐stage continuous foam fractionation column. Enrichments ranged from 1.5 to 6.0 and recoveries from 5 to 85%. The feed concentrations were varied from 0.01 to 0.2 wt %, and enrichments were found to increase with lower feed concentrations. Enrichments also increased with lower superficial gas velocities and larger bubble sizes. At sufficiently low feed flow rates, enrichment was found to increase with an increase in the flow rate, eventually becoming insensitive to the feed flow rate at higher values. The pH was varied from 3.5 to 7.0 and ionic strength from 0.001M to 0.2M. The effects of pH and ionic strength were found to be coupled with bubble size. A minimum bubble size was found at pH 4.8, the isoelectric point of BSA, resulting in a minimum in the enrichment. Bubble size, and thus enrichment, was found to increase as the ionic strength decreased from 0.2M to 0.01M. Previous models1,2 for the hydrodynamics of foam column were extended for a singlestage continuous foam fractionation column for the prediction of enrichment and recovery. The model assumed adsorption equilibrium, infinite surface viscosity, and bubbles of the same size. Though coalescence was formally accounted for in the model by considering bubble size as a function of foam height, calculations for the experimental runs were performed only for the case of no coalescence. Quantitative predictions of enrichment and recovery could not be made with a single representative bubble size because of the broad inlet bubble size distribution as well as broadening of the distribution as a result of coalescence. The experimental enrichments were higher and recoveries were lower than the model predictions, the discrepancy being more pronounced at lower feed concentrations because of increased coalescence. The higher enrichments are due to the predominant effect of internal reflux as a result of coalescence whereas the lower recoveries are a result of detrimental effects of broadening bubble size distributions.