bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of enzyme concentration on the rate of the hydrolysis of cellulose
Authors: Sattler W. , Esterbauer H. , Glatter O. , Steiner W. 
Published: December 2004

AbstractThe relationship among extent of hydrolysis, reaction time, and enzyme dosage was investigated. For this, Sigmacell 50 and pretreated poplar wood (20 g/L) was hydrolyzed with varying dosages of cellulases from three different sources (5 to 100 FPU/g) for time periods ranging from 2 to 94 h. It was found that the formation of glucose can be described by summation of two parallel first order reactions. The extent of hydrolysis at fixed time increases with increasing enzyme dosage in a hyperbolic function. From the empirical data it is possible to calculate the fractions of easily and difficult hydrolyzable cellulose and the digestability which could maximally be obtained at infinite enzyme loadings. In the system Sigmacell 50 and Celluclast the easily and difficult hydrolyzable components are 43.0 and 57.0%, respectively, and the maximum digestability at 94 h is 82.6%. Poplar wood, steam treated at 200°, 220°, and 240°C, showed with Celluclast at 24 h a maximum digestability (weight percentage of wood degraded to glucose) of 43.9, 64.9, and 68.0%. The relationships derived from experimental data allow one to compare objectively the effectiveness of different cellulase enzymes and different pretreatments.
Design of a lamella settler for biomass recycling in continuous ethanol fermentation process
Authors: Tabera J. , Iznaola M. A. 
Published: December 2004

AbstractThe design and application of a settler to a continuous fermentation process with yeast recycle were studied. The compact lamella‐type settler was chosen to avoid large volumes associated with conventional settling tanks. A rationale of the design method is covered. The sedimentation area was determined by classical batch settling rate tests and sedimentation capacity calculation. Limitations on the residence time of the microorganisms in the settler, rather than sludge thickening considerations, was the approach employed for volume calculation. Fermentation rate tests with yeast after different sedimentation periods were carried out to define a suitable residence time. Continuous cell recycle fermentation runs, performed with the old and new sedimentation devices, show that lamella settler improves biomass recycling efficiency, being the process able to operate at higher sugar concentrations and faster dilution rates.
Dynamic modeling of immobilized cell reactor: Application to ethanol fermentation
Authors: Nakasaki Kiyohiko , Murai Takeji , Akiyama Tetsuo 
Published: December 2004

AbstractA mathematical model has been developed for the unsteady‐state operation of an immobilized cell reactor. The substrate solution flows through a mixed‐flow reactor in which cells immobilized in gel beads are retained. The substrate diffuses from the external surface of the gel beads to some internal location where reaction occurs. The product diffuses from the gel beads into liquid medium which flows out of the reactor. The model combines simultaneous diffusion and reaction, as well as cell growth, and it can predict how the rates of substrate consumption, product formation, and cell growth vary with time and with initial conditions. Ethanol fermentation was chosen as a representative reaction in the immobilized cell reactor, and numerical calculations were carried out. Excellent agreement was observed between model predictions and experimental data available in the literature.
Characterization of production of free gluconic acid by Gluconobacter suboxydans adsorbed on ceramic honeycomb monolith
Authors: Shiraishi Fumihide , Kawakami Koei , Kono Seiji , Tamura Akihiko , Tsuruta Satoshi , Kusunoki Koichiro 
Published: December 2004

AbstractGluconobacter suboxydans IFO 3290 was immobilized by adsorption on ceramic honeycomb monolith and continuous production of free gluconic acid from glucose was performed in an aerated reactor. The effects of reactor residence time, aeration rate, and glucose concentration were investigated on the gluconic acid yield. Observation of SEM photographs revealed that the cells were adsorbed with a high density not only on the outer surface of the support but also on the inner surface of large pores. From measurement of the number of the adsorbed cells, it was elucidated that the biofilm comprised a monolayer or bilayer of the cells. Maximum specific rate of growth was estimated for the free and adsorbed cells, and the adsorbed cells were found to grow at a fast rate compared with the free cells. In the continuous fermentation performed for one month at the glucose concentration of 100 kg/m3, reactor residence time of 3.5 h and aeration rate of 900 cm3/min, the activity of the adsorbed cells was appreciably stable. The high productivity of 26.3 kg/(m3‐reactor · h) was attained with the gluconic acid yield of 84.6% and glucose conversion of 94%.
Further kinetic characterization of alginate‐entrapped cells of Mucuna pruriens L.
Authors: Pras Niesko , Hesselink Paul G. M. , Guikema Wiebout M. , Malingré Theo M. 
Published: December 2004

AbstractAlginate‐entrapped cells of Mucuna pruriens L. hydroxylate L‐tyrosine, tyramine, para‐hydroxyphenylpropionic acid, and para‐hydroxyphenylacetic acid to their corresponding catechols, which were released into the incubation medium. Michaëlis‐Menten kinetics was applied for each bioconversion. The apparent affinity constants were comparable with the affinity constants obtained with a homogenate directly prepared from the cells used for entrapment and with a derived partly purified phenoloxidase. The values found for the apparent maximum rates of bioconversion of the entrapped cells were ca. 50% of the values of the maximum rates of bioconversion of the cell homogenate, indicating that the entrapped cell system was not operating optimally. The effective diffusivities of the substrates and products were measured with alginate‐entrapped, inactivated cells. From the five inactivation methods tested, glutaric aldehyde treatment was chosen as the general procedure. Calculated effective diffusivities for the monophenols and catechols demonstrated that these compounds could diffuse freely into and out of the beads. For each bioconversion, the observable modulus was calculated from the initial rate of bioconversion and the effective diffusivity of the substrate. The resulting values indicated that the diffusional supply rate of the substrates was not the limiting factor, except for the conversion of tyramine for which a modulus higher than one was obtained. Analogously, the observable moduli were calculated for oxygen, which was utilized for bioconversion and cell respiration, and these values pointed towards strong oxygen limitation in all cases. The bioconversion rates of the entrapped cells increased with decreasing cell aggregate size. Therefore, it was concluded that direct cell‐matrix contact determined the amount of phenoloxidase involved in the bioconversions. The bioconversion rate on a protein basis was constant with enhancement of the bead charge and thus, in spite of limitations, the mixing conditions as such were relatively optimal. In conclusion, the nonoptimal efficiency of the plant cell system studied was caused by oxygen limitation and a partial phenoloxidase participation, but not by mass transfer limitations for substrates and products with the exception of the conversion of tyramine into dopamine.
Characteristics of immobilized lipase‐catalyzed hydrolysis of olive oil of high concentration in reverse phase system
Authors: Kang Sung Tae , Rhee Joon Snick 
Published: December 2004

AbstractCandida rugosa lipase immobilized by adsorption on swollen Sephadex LH‐20 could almost completely hydrolyze 60% (v/v) olive oil in isooctane. Kinetic analysis of the lipase‐catalyzed hydrolysis reaction was found to be possible in this system. Amount of fatty acids produced was linearly proportional to the enzyme concentration of 720 μg/g wet gel. The specific enzyme activity was 217 units/mg protein at 60% (v/v) olive oil concentration. When the initial rate is plotted versus concentration of olive oil, this system did not follow Michaelis‐Menten kinetics. Maximum activity was obtained at pH 7, but optimum temperature shifted towards higher one with the increase of olive oil concentration. Among the various chemical compounds tested, Hg2+ and Fe2+ inhibited the lipase seriously. As the concentration of olive oil increased, the rate of the hydrolysis also increased, but degree of the hydrolysis was observed to decrease. The supply of water from the inside of the gel to the surface of the gel was the main factor for the control of the rate of hydrolysis in batch hydrolysis. The immobilized lipase was used to hydrolyze olive oil two times. Achievement of chemical equilibrium took a longer time with the addition of water and the degree of hydrolysis decreased in the second consecutive trial. After the second hydrolysis trial, the gels were regenerated in a packed column first by eluting out both residual fatty acids around the gel particles and the accumulated glycerol with ethanol and then with 0.05M phosphate buffer, pH 7. The immobilized lipase on the regenerated gel showed the same hydrolysis activity as the original one.
Effect of number of turbine impellers on surface aeration in laboratory fermentor
Authors: Veljković Vlada , Skala Dejan 
Published: December 2004

AbstractThe effect of one and two four‐flat‐bladed turbine impellers on the surface aeration intensity in a laboratory tormentor was investigated at different agitation speeds and sparge rates. The surface aeration was found to be generally more intensive with two impellers for the same other operating conditions because of higher power consumption and the position of the upper impeller closer to the free liquid surface. The surface aeration intensity was successfully correlated in terms of power consumption and sparge rate. The aeration number alone cannot be used for general predicting surface aeration intensities.
Biotransformation of acrylonitrile to acrylamide using immobilized whole cells of Brevibacterium CH1 in a recycle fed‐batch reactor
Authors: Hwang Jun Sik , Chang Ho Nam 
Published: December 2004

AbstractAcrylamide was produced from acrylonitrile using immobilized Brevibacterium CH1 cells that were isolated from soil and found to possess nitrile hydratase activity. The reaction conditions and stability of the enzyme activity were studied. The conversion yield was nearly 100%, including a trace amount of acrylic acid. This strain showed strong activity of nitrile hydratase toward acrylonitrile and extremely low activity of amidase toward acrylamide. A packed bed reactor was operated in a fed‐batch manner for acrylamide production of high concentration. The acrylonitrile concentration was maintained below 3% and the operating temperature at 4°C to minimize enzyme deactivation.
Medium‐induced inhibition of microbial adsorption to nickel and activated charcoal
Authors: Protheroe R. G. , Cumming R. H. , Matchett A. 
Published: December 2004

AbstractEquilibrium adsorption studies on Escherichia coli and Saccharomyces sp. revealed the capacity and affinity of these organisms for the surfaces of powdered charcoal and nickel. In simple salt solutions both organisms readily adsorbed to each solid with an affinity and maximum loading capacity individual to each cell–solid combination. In the presence of common growth media (lab‐lemco, nutrient broth, peptone, and yeast extract, individually at a concentration of 1.3%), each medium substantially inhibited adsorption. Each medium contained a protein‐aceous constituent as determined by ultraviolet (UV) analysis. The degree of inhibition was relative to medium concentration present during assay. Cell wall extracts from whole‐yeast cells also effectively inhibited adsorption. Cells adsorbed in the presence of sodium chloride solutions were susceptible to subsequent desorption by nutrient broth.
Dependence of in vivo inactivation kinetics of gramicidin S synthetase on cell physiology
Authors: Tasker James C. , Agathos Spiros N. 
Published: December 2004

AbstractGramicidin S synthetase, the enzyme complex catalyzing the biosynthesis of the antibiotic gramicidin S in Bacillus brevis, is subject to O2‐dependent in vivo inactivation during exponential aerobic growth after reaching a peak in specific activity. The five amino acid substrates of the synthetase are capable of stabilizing its activity to varying degrees in whole cells shaken aerobically. Depending on the time of cell harvesting before, during, or after the peak in intracellular gramicidin S synthetase specific activity, the enzyme has a long, medium, or short half‐life, respectively. The kinetic profiles of gramicidin S synthetase in B. brevis cells indicate that both the kinetics of synthetase loss and the degree of its amino‐acid‐mediated stabilization are a strong function of the cells' physiological development.
Improvement of aerobic treatment process by cross‐linked polyvinylpyridine
Authors: Kawabata Nariyoshi , Oda Masakatsu 
Published: December 2004

AbstractIn continuous aerobic treatment of artificial sewage by activated sludge, the rate of removal of chemical oxygen demand (COD) was markedly enhanced by the presence of cross‐linked poly‐4‐vinylpyridine (PVP). The concentration of dissolved oxygen (DO) was also low in the presence of PVP. The extent of improvement in COD removal increased with increases in substrate load and the surface area of the PVP in the working space of the test apparatus. These results suggest an increase of the bacterial population resulting from the presence of the PVP. However, formation of measurable biofilm was not detected on the surface of the PVP during continuous aerobic treatment.
Optimization of fermentation processes using recombinant Escherichia coli with the cloned trp operon
Authors: Park Tai Hyun , Seo Jin‐Ho , Lim Henry C. 
Published: December 2004

AbstractOptimal operating conditions have been determined for recombinant Escherichia coli cells in a fed‐batch and two‐stage continuous fermentors. The model expression system used in this article was the E. coli trp promoter cloned on plasmids. Model equations for cell growth and cloned‐gene expression have been formulated and used to evaluate process performances under different operating modes. The operating variables manipulated for maximum performance include the timing of IAA addition to derepress transcription from the trp promoter. The total operating period and the nutrient concentration profile during fermentations. For a fed‐batch mode, the performance was significantly improved by adjusting the IAA addition (environmental switch) time relative to the total operation period. It was found that the optimal switching time exists for a given total operation period. For a two‐stage continuous fermentation system, the productivity is more sensitive to the combination of the dilution rates than to the volume ratio of two reactors. In general, as long as the down time is less than the total operation time in the fed‐batch mode, the fed‐batch mode gives higher productivity than the two‐stage continuous system.
Assessment of macroenergetic parameters for an anaerobic upflow biomass bed and filter (UBF) reactor
Authors: Guiot S. R. , Podruzny M. F. , McLean D. D. 
Published: December 2004

AbstractThis article reports the steady‐state performance of two hybrid anaerobic digesters treating soluble synthetic sugar wastes of 1 and 0.5% strength and the assessment of the associated macroenergetic parameters (growth yield, so‐called maintenance coefficient). A theoretical development shows a “nongrowth” parameter concept to be more appropriate than maintenance or decay. Combined energy and mass balances are used to develop a model for growth rate which compares well with experimental data. The COD removal efficiency had no significant effect on growth yield and the maintenance parameter, although a dual combined balance indicated the possibility of such an effect. Macroenergetic parameters did not vary significantly with the specific feeding rate of the system. We thus conclude that a single model may be used over a broad range of feeding and performance conditions.
Extraction of monocrotaline from Crotalaria spectabilis using supercritical carbon dioxide and carbon dioxide–ethanol mixtures
Authors: Schaeffer Steven T. , Zalkow Leon H. , Teja Amyn S. 
Published: December 2004

AbstractMonocrotaline, a pyrrolizidine alkaloid of chemotherapeutic interest, was successfully extracted from the crushed seeds of Crotalaria spectabilis using supercritical carbon dioxide and ethanol mixtures. Overall solubilities of the plant material in the supercritical fluid phase were as high as 1.1 mass percent, and monocrotaline solubilities were as high as 0.07 mass percent. The solubility of monocrotaline in the presence of other plant material was smaller by 50 to 98% compared with the solubility of pure monocrotaline in the supercritical fluid. Also, it was found that the extraction of the complex plant material was time‐dependent after approximately one percent of the original mass of the material had been extracted.
Adsorption equilibrium in immunoaffnity chromatography with antibodies to synthetic peptides
Authors: Kondo Akihiko , Takamatsu Hiroyuki , Katoh Shigeo , Sada Eizo 
Published: December 2004

AbstractThe effects of charged residues in peptide antigens on the binding characteristics of polyclonal antipeptide antibodies were studied using immunoadsorbents prepared by coupling the antibodies to CNBr‐activated Sepharose 4B. Among the antipeptide antibodies, an antibody to the peptide without charged residues showed the most stable interaction with the peptide to the changes in pH. Conversely, the binding affinity of antibodies to the pep‐tides with histidine residues having a unique pKa value of 6.0 decreased steeply with pH at around 6.0. The binding affinity of an antibody to the peptide with many charged residues decreased steeply with an increase in the ionic strength (adjusted by NaCl). Since circular dichroism (CD) spectrum measurements indicate that these peptides show disordered structures in the pH range of adsorption measurement, the dependence of peptide‐antibody interaction on environmental conditions is attributed to the characteristics of side chains of the peptides. These results indicate that the dependence of the binding affinity of antipeptide antibodies on pH and the ionic strength is dominantly affected by the number and the pKa values of charged residues in the peptides.
Production of glycerides from glycerol and fatty acid by immobilized lipases in non‐aqueous media
Authors: Ergan F. , Trani M. , André G. 
Published: December 2004

AbstractImmobilized Mucor miehei lipase catalyzes synthesis reactions between glycerol and oleic acid. No organic solvent is necessary to solubilize the substrates, which allows for the use of a reaction medium solely composed of the necessary substrates. Water produced in the reaction evaporates due to the high temperature used for the process. A conversion of 86% of oleic acid into triolein is obtained when using the substrates in stoichiometric amounts. Varying the ratio of glycerol over oleic acid allows for the preferential synthesis of one of the glycerides. Some batch reactors have been set up using different means of removing the water: spontaneous evaporation, molecular sieves, vacuum, and dry air bubbling.
Extractive acetonobutylic fermentation by coupling ultrafiltration and distillation
Authors: Minier M. , Grateloup R. , Blanc‐Ferras E. , Goma G. 
Published: December 2004

AbstractAn extractive acetonobutylic fermentation process is developed by integrating bioproduction, Ultrafiltration, and distillation, providing simultaneous retention of biomass, selective removal of inhibitors from the permeate, as well as separation and purification of acetone–butanol–ethanol solvents. Successive batch fermentations were performed with normal pressure distillation (98°C), which permitted prolonging and enhancing (by a factor of 3) solvent production, with very few volume exchanges of medium (average dilution rate ws 0.002 h−1), and recovering on‐line concentrated solvents. Different operating conditions were also tested in order to study the presence of extracellular autolytic enzymes as inhibition factors: It was shown that, (1) extracellular autolytic activity remains low during the larger part of fermentations, even without enzyme‐inactivating thermotreatment in the distillation boiler, and (2) high‐temperature distillation causes deleterious effects to the culture medium for long duration treatments. Progressive improvements of the process were achieved, first, by managing continuous runs, providing a minimum renewal of the culture medium and, mainly, by decreasing temperature and pressure of distilation. Solvent productivity then reached 2.6 g/L h for a 0.036 h−1 average dilution rate, corresponding to a feed concentration of 156 g/L glucose actually consumed.
The effect of agitation on the morphology and penicillin production ofPenicillium chrysogenum
Authors: Smith J. J. , Lilly M. D. , Fox R. I. 
Published: December 2004

AbstractPenicillium chrysogenumstrain P1 was grown on complex media in 10 and 100 L agitated fermenters at various aeration rates and stirrer speeds. Samples were removed at intervals for measurements of the culture morphology. At high stirrer speeds (1000 and 1200 rpm) in 10‐L fermentations the rate of decrease in the mean effective hyphal length was faster and the rate of penicillin production was lower than fermentations done at 800 rpm. At similar power inputs per unit volume in 100‐L fermentations, the change in mean effective hyphal length was less and higher penicillin production rates were observed. This work comparing the results at two scales has shown that neither of the concepts of impeller tip speed or the dissipation rate of turbulence have general validity as a measure of hyphal damage. Our results are reasonaby well correlated by groups similar to circulation rate (ND/V) with lower circulation rates being beneficial. An adaptation of the van Suijdam and Metz relationship, expressed asP/Dtc, was most successful. Our data are insufficient to demonstrate the generality of the relationship but do support the concept of a dispersion zone around the impellers in which mycelia may be damaged. The greater the frequency of circulation of mycelia through the zone the greater the damage and the lower the rate of penicillin synthesis by the culture.
Effects of spatial heterogeneity on the dynamics of a microbial feeding interaction
Authors: Tsangaropoulou Esperia , Pavlou Stavros 
Published: December 2004

AbstractA mathematical model for an ideal chemostat in which one microbial population feeds on another and where Monod's model is used for the specific growth rates of both populations predicts a less stable behavior for the system than the one observed experimentally. Various factors have been proposed as being the reason for the increased stability of such systems. In this work, the effect of spatial heterogeneity on the dynamics of the microbial feeding interaction is studied. It is concluded that spatial heterogeneity has a stabilizing effect on the system. This effect combined with other factors could be the reason for the increased stability observed in systems where a microbial feeding interaction occurs.