bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production L‐tryptophan by Escherichia coli cells
Authors: Bang Won‐Gi , Lang Siegmund , Sahm Hermann , Wagner Fritz 
Published: December 2004

AbstractWhole cells of Escherichia coli B 10 having high tryptophan synthetase activity were used directly as an enzyme source to produce L‐tryptophan from indole and L‐ or D,L‐serine. This strain is tryptophan auxotrophic, which is tryptophanase negative and, in addition, L‐ and D‐serine deaminase negative under production conditions. To avoid inhibition of tryptophan synthetase by a high concentration of indole, nonaqueous organic solvents, Amberlite XAD‐2 adsorbent, and nonionic detergents were used as reservoirs of indole in the reaction mixture for the production of L‐tryptophan. As a result, different effects were observed on the production of L‐tryptophan. Particularly, among the nonionic detergents, Triton X‐100 was very efficient. Using Triton X‐100 for production of L‐tryptophan from indole and L‐ or D,L‐serine by whole cells of Escherichia coli B 10, 14.14 g/100 mL and 14.2 g/100 mL of L‐tryptophan were produced at 37°C for 60 h.
Continuous production of L‐tryptophan from indole and L‐serine by immobilized Escherichia coli cells
Authors: Bang Won‐Gi , Behrendt Ulrich , Lang Siegmund , Wagner Fritz 
Published: December 2004

AbstractEscherichia coli B 10, which has high activity of tryptophan synthetase, was grown in a 50‐L batch culture in order to determine in which growth phase the cells have the highest specific tryptophan productivity. Accordingly, whole cells of the stationary phase were used for immobilization in polyacrylamide beads. After immobilization, these immobilized cells had 56% activity of tryptophan synthetase compared with that of free cells. First, the properties of immobilized cells were investigated. Next, discontinuous productions of L‐tryptophan were carried out by using immobilized cells. In discontinuous production of L‐tryptophan by the batch, the activity remaining of immobilized cells was 76–79% after 30 times batchwise use. In continuous production of L‐tryptophan with a continuous stirred tank reactor (CSTR), the activity remaining of the immobilized cells was 80% after continuous use for 50 days. The maximum productivity of L‐tryptophan in this CSTR system was 0.12 g tryptophan L−1 h−1.
Effect of chemical modification of cellulose on the activity of a cellulase from Aspergillus niger
Authors: Boyer Rodney F. , Redmond Molly A. 
Published: December 2004

AbstractFive chemically modified forms of cellulose were prepared, characterized, and tested as substrates for a homogeneous glucanohydrolase from A. niger. The relative order of reactivity at pH 4.0 was DEAE = PEI > benzyl DEAE > cellulose > P > CM.The following abbreviations are used throughout the article: (RBB) Remazol brilliant blue R; (DEAE) diethylamino ethyl; (PEI) polethyleneimine; (CM) carboxymenthyl; (P) phospho; (DS) degree of RBB dye substitution of cellulose, in mol dye/100 glucose.
This indicates that positively charged cellulose substrates are more susceptible to hydrolysis by the cellulase. This observation strengthens an earlier proposal that caroxyl groups on the enzyme are involved in substrate binding and catalytic action. Chemical modification is suggested as a method to increase the rate of enzymatic hydrolysis of cellulose, a process now in the commercial development stage.
Some fluidization characteristics of biological beds
Authors: Hermanowicz S. W. , Ganczarczyk J. J. 
Published: December 2004

AbstractThe free‐fall terminal velocity of particles coated with a nitrifying biofilm was investigated. The drag force exerted by the liquid on a biocoated particle was found larger than that for an uncoated particle. A new formula for the drag coefficient was proposed. The wet density of biofilm was estimated as 1.14 g/cm3. A proposed modification of the Zaki‐Richardson method was successfully used for calculations of the porosity of a fluidized bed.
Production of biomas and β‐D‐galactosidase by Candida pseudotropicalis grown in continuous culture on whey
Authors: Gomez Amand , Castillo Francisco J. 
Published: December 2004

AbstractThe production of biomass and β‐D‐galactosidase by the lactose‐utilizing yeast Candida pseudotropicalis NCYC 744 in whey medium was studied. Apparent optimization of growth conditions and medium was done in continuous culture. Optimaql pH and temperature were 2.6 and 36–38°C, respectively, Limitations in Cu, Zn, and possbily Mn were detected in deproteinized whey medium. Additions of tryptophan estimulated growth of the yeast. Under optimal conditions in medium supplemented with excess tryptophan, Cu, Zn, and Mn the maximum values obtained: yeast concentration, 4.6 g/L; yeast productivity, 1.4 g/L h (at D = 0.35 h−1); enzyme volumetric productivity, 2100 U/L h (at D = 0.25 h−1); maintenance coefficient, 5–10 mg lactose/g cell h; saturation constant (Ks) for lactose, 4.76mM; maximum specific growth rate, (μmax), 0.47 h−1. No significant increase in specific enzyme activity (U/mg cell) was observed after medium optimiztion evidencing the importance of regulatory controls in enzyme synthesis.
Oxygen electrode dynamics: Three‐layer model—chemical reaction in the liquid film
Authors: Linek V. , Sinkule J. , Vacek V. 
Published: December 2004

AbstractA general model of the transient behaviour of an oxygen probe is derived on more general assumptions than those previously considered. The present state of the art is shorly discussed in its relation to the newly derived equations: (1) the reducibility of the three‐layer diffusional model to two‐layer ones is discussed, and the two‐layer model considering the membrane and the liquid film is verified experimentally, (2) experimental and theoretical treatments of transient probe characteristics determination are examined, and (3) the influence of chemical reactions of the first order as well as of zero order (microorgaganism respiration) in measured media on transientd probe characteristics is quantified.
Dependence of biological treatment rate on species composition in activated sludge or biofilm. II: From models to theory
Authors: Vavilin V. A. 
Published: December 2004

AbstractTraditional biological treatment models are “deduced” from formal chemical kinetics or dynamics of pure microorganism cultures growth. The best formal models give reasonable approximations of the biological treatment model with an ecosystem adaptation (ESA model). The model presented here explains some features of the biological treatment mechanism that cannot be described by formal models.
Mass transfer parameters in an immobilized glucoamylase column by pulse response analysis
Authors: Sirotti David A. , Emery Alden 
Published: December 2004

AbstractPulses of several nonreacting solutes were fed to a column containing immobilized enzyme catalyst beads. The response curves were recorded, and their first and second moments were determined by numerical integration. From the moment analysis, the void volume, internal porosity, and tortuosity of the support were calculated.
A Process for large‐scale isolation of β‐galactosidase from E. coli in an aqueous two‐phase system
Authors: Veide Andres , Smeds Anna‐Lisa , Enfors Sven‐Olof 
Published: December 2004

AbstractA method suitable for large‐scale isolation of β‐galactosidase from a suspension of disintegrated E. coli cells has been developed. In an aqueous two‐phase system consiting of PEG 6000 and potassium phosphate, all cell debris and the major part of the proteins and nucleic acids were partitioned to the denser salt phase. Seventy‐five percent of the β‐galactosidase was recovered in the lighter PEG phase, giving a purification ratio of about 12.
Occurrence of glutamate dehydrogenase isoenzymes during growth of Oocystis alga
Authors: Lee B. H. , Picard G. A. 
Published: December 2004

AbstractOocystis sp., a unicellular green alga, contained two glutamate dehydrogenase isoenzymes: one was specific for NADH and the other for NADPH. Activity staining after gel electrophoresis indicated that one component in NADH‐GDH was not specific for the cofactor and three components in NADPH‐GDH. The optimal concentration of substrate, purification procedure and kinetic properties of both glutamate dehydrogenase (GDH) enzymes in vitro are presented. The kinetics of growth, nutrient removal and enzyme activities for Oocystis growing in wastewater showed that ammonia was preferentially utilized over nitrate and the medium was depleted before the maximum population was obtained in indoor culture. There was a sharp increase in NADPH‐GDH activity following the exhaustion of ammonia from the medium but NADH‐GDH activity remained unchanged. The NADPH‐GDH activity at the outset increased exponentially with time in greenhouse culture but then decreased sharply accompained by a rapid increase in biomass and nitrite concentration. The Km values for ammonia in this algal GDH was high, while glutamate synthase activity was not detected; this suggests that Oocystis may adapt to conditions of ammonia limitation by producing large quantities of NADPH‐GDH instead of using glutamate synthase pathway.
Modeling of experiments on biofilm penetration effects in a fluidized bed nitrification reactor
Authors: Denac M. , Uzman S. , Tanaka H. , Dunn I. J. 
Published: December 2004

AbstractA four‐component, diffusion‐reaction model with double Michaelis‐Menten kinetics was used to describe the experimental data obtained from a laboratory biofilm, fluidized‐bed nitrification reactor. Theory and experiment demonstrated that the stoichiometric ratio (3.5 mg O2/mg NH‐N) can be employed as a criterion to determine whether the limiting substrate is oxygen or ammonia. For the present work, in the range of concentrations where limitation occurred, 4 mg/L NH‐N and 14 mg/L O2, the ratio of oxygen to ammonia in the bulk liquid determined which substrate was penetration‐limiting—O2 if <3.5 and NH if > 3.5. Halforder kinetics with respect to the limiting substrate described the apparent overall rates. Simulations provided biofilm concentration profiles which demonstrated the role of the oxygen‐ammonia ratio. Experiments indicated that, generally, high NO concentrations can be expected. These depend on the residence time, biofilm area, and oxygen concentration. This dependency was investigated with the model, as was the parametric sensitivity with respect to the saturation constants. Particularly important for the NO levels were the ratios of the saturation constants for oxygen.
Immobilization of glucoamylase and glucose oxidase in activated carbon: Effects of particle size and immobilization conditions on enzyme activity and effectiveness
Authors: Bailey James E. , Cho Y. K. 
Published: December 2004

AbstractGlucoamylase and glucose oxidase have been immobilized on carbodiimide‐treated activated carbon particles of various sizes. Loading data indicate nonuniform distribution of immobilized enzyme within the porous support particles. Catalysts with different enzyme loading and overall activities have been prepared by varying enzyme concentration in the immobilizing solution. Analysis of these results by a new method based entirely upon experimentally observable catalyst properties indicates that intrinsic catalytic activity is reduced by immobilization of both enzymes. Immobilized glucoamylase intrinsic activity decreases with increasing enzyme loading, and similar behavior is suggested by immobilized glucose oxidase data analysis. The overall activity data interpretation method should prove useful in other immobilized enzyme characterization research, especially in situations where the intraparticle distribution of immobilized enzyme is nonuniform and unknown.
Least‐squares estimation of batch culture kinetic parameters
Authors: Ong S. L. 
Published: December 2004

AbstractThis article concerns the development of a simple and effective least‐squares procedure for estimating the kinetic parameters in Monod expressions from batch culture data. The basic approach employed in this work was to translate the problem of parameter estimation to a mathematical model containing a single decision variable. The resulting model was then solved by an efficient one‐dimensional search algorithm which can be adapted to any microcomputer or advanced programmable calculator. The procedure was tested on synthetic data (substrate concentrations) with different types and levels of error. The effect of endogeneous respiration on the estimated values of the kinetic parameters was also assessed. From the results of these analyses the least‐squares procedure developed was concluded to be very effective.
Rotating drum fermentor for plant cell suspension cultures
Authors: Tanaka Hideo , Nishijima Fuyuhiko , Suwa Mitsuru , Iwamoto Tetsuya 
Published: December 2004

AbstractA rotating drum fermentor designed for plant cell suspension cultures was constructed and tested. The oxygen transfer coefficient (kLa) and power requirements in the fermentor were determined with the water system under various conditions and the relationship between them in the fermentor was clarified. Also, the relationship between kLa and the apparent viscosity in the fermentor was investigated in the cell suspension system. The rotating drum fermentor was found to be superior to the mechanically agitated fermentor in the capacity of oxygen supply under high viscosity and low hydrodynamic stress conditions. This finding was also confirmed by the experiments with plant cell suspension cultures.
Enzyme electrode for specific determination of L‐lysine
Authors: Romette J. L. , Yang J. S. , Kusakabe H. , Thomas D. 
Published: December 2004

AbstractL‐Lysine α‐oxidase from Trichoderma viride Y244‐2 is immobilized in a gelatin support and fixed on a pO2 sensor. The enzyme electrode obtained is used in a continuous flow system in order to measure the concentration of L‐lysine in a fermentor. The sample oxygen‐content dependance of the signal is minimized because of the enzyme support properties. The enzyme electrode response is set for lysine concentration from 0.2mM to 4mM. The specificity of lysine is tested with other amino acids. The enzyme membrane for lysine electrode can be used 3000 times or stored six months with good stability.
Catalytic solvent delignification of agricultural residues: Organic catalysts
Authors: Ghose T. K. , Pannir Selvam P. V. , Ghosh P. 
Published: December 2004

AbstractThe effects of moderate‐temperature aqueous butanol pretreatment of rice straw on several organic catalysts have been studied. Maximum delignification was obtained with an aromatic organic acid catalyst. Presoaking of straw in aqueous improved delignification, particularly in high solid–liquid rations. However, due to the difficulty of penetration of lignin into the solvent phase, an increase in the solid‐liquid ratio appears to affect delignification. A two‐stage catalytic solvent process involving presoaking at 80°C followed by delignification at 120°C resulted in 83% removal of lignin in aqueous‐butanol, whereas 75% lignin removal was possible in ethanol. Higher reduction in the crystallinity was possible with etanol. Lignin produced by the solvent process offers desirable physical properties for polymer applications compared to Kraft lignin.
A kinetic model for the activated sludge process which considers diffusion and reaction in the microbial floc
Authors: Benefield Larry , Molz Fred 
Published: December 2004

AbstractA mathematical model has been developed which describes substrate removal, oxygen utilization, and biomass production in an aggregated microbial suspension containing the substrate as a soluble biodegradable material and a uniform floc size. It is applicable to both steady‐state and transient conditions. The model, consisting of three partial differential equations and two ordinary differential equations, takes into account the flow pattern in the reactor, intraparticle mass transport of oxygen and substrate, and biochemical reaction by individual cells embedded in the floc. Efficient numerical solution of the coupled nonlinear equations is obtained using an implicit finite difference approach for both the reactor and floc equations. A convergent solution is realized through block interation utilizing the tridiagonal algorithm. Results indicate that a unifying theory of activated sludge dynamics will have to consider coupling between floc chemical kinetics and changes in the bulk liquid characteristics. Floc size emerges as an important influence on system performance. It appears necessary to distinguish between a system response caused by diffuslonal resistances and nutrient limitations within the floc and a response caused by physiological adaption when analyzing the transient behavior of an activated sludge process. Future research should be devoted to rigorous laboratory determinations of model parameters along with extensions to include limitations of nutrients other than orgabnic carbon and oxygen.
Effect of gamma‐ray irradiation on alcohol production from corn
Authors: Han Y. W. , Cho Y. K. , Ciegler A. 
Published: December 2004

AbstractCracked corn was irradiated with gamma rays at 0–100 Mrad and the effects of the irradiation on sugar yield, susceptibility to enzymatic hydrolysis of starch, yeast growth, and alcohol production were studied. Gamma irradiation at 50 Mrad or greater produced a considerable amount of reducing sugar but little glucose. At lower dosages, gamma irradiation significantly increased the susceptibility of corn starch to enzymatic hydrolysis, but dosages of 50 Mrad or greater decomposed the starch molecules as indicated by the reduction in iodine uptake. About 12.5% reducing sugar was produced by amylase treatment of uncooked, irradiated corn. This amount exceeded the level of sugar produced from cooked (gelatinized) corn by the same enzyme treatment. The yeast numbers in submerged cultivation were lower on a corn substrate that was irradiated at 50 Mrad or greater compared to that on an unirradiated control. About the same level of alcohol was produced on uncooked, irradiated (105−106 rad) corn as from cooked (121°C for 30 min) corn. Therefore, the conventional cooking process for gelatinization of starch prior to its saccharification can be eliminated by irradiation. Irradiation also eliminated the necessity of sterilization of the medium and reduced the viscosity of high levels of substrate in the fermentation broth.
Theory and applications of unstructured growth models: Kinetic and energetic aspects
Authors: Esener A. A. , Roels J. A. , Kossen N. W. F. 
Published: December 2004

AbstractMicrobial kinetics and energetics are discussed in connection with the formulation of unstructured growth models. The development of microbial energetics and the use of macroscopic methods in the study of microbial growth are briefly evaluated. The general approach to the modelling of microbial growth has been critically discussed and a strategy for the formulation of unstructured models is presented. A simple unstructured model based on Monod kinetics and the linear relation for substrate consumption is evaluated with reference to extensive experimental and simulation data obtained in batch, fed‐batch, and continuous cultivation modes. Choice for a kinetic expression is discussed and has been shown not to be critical in most situations. It is shown that during growth in batch mode, the behavior of the system is rigidly fixed by the kinetic parameter: the maximum specific growth rate. The energetic parameters have minimal influence. In continuous cultivation the behavior is fixed by the energetic parameters: the maximum yield and the coefficient of maintenance. Implications of these observations have also been discussed. The linear relation for substrate consumption is tested with continuous culture data. It is shown that significant deviations at low growth rates cannot be fully accounted by the loss of viability. The situations where unstructured models will be adequate or not for system description, are evaluated and checked experimentally. Influence of an environmental factor, the temperature, on the unstructured model parameters is also quantitatively described. It is concluded that the art of unstructured model building has already reached its maturity and that now much effort should be channelled into the development and verification of structured models.
Effect of glucose and other sugars on the β‐1,4‐glucosidase activity of Thermomonospora fusca
Authors: Ferchak John D. , Pye E. Kendall 
Published: December 2004

AbstractThe cell‐associated β‐glucosidase activity of Thermomonospora fusca, strain YX, showed both PNPGase and cellobiase activities. The cellobiase activity was found by HPLC assay to have very low product inhibition, whereas the PNPGase activity was more significantly inhibited. Of the various sugars and sugar analogs tested for inhibition of the PNPGase activity, gluconolactone had the greatest effect. The low product inhibition of the cellobiase activity was further demonstrated by the production of glucose syrups to 20% concentration from both cellobiose and swollen cellulose (Avicel). This characteristic is of practical importance in the development of a commercial process for the production of glucose syrups from cellulose. Growth experiments gave further evidence for the probability of separate enzymes for the PNPGase and cellobiase activities.
Reaction characteristics of an immobilized yeast producing ethanol
Authors: Furusaki Shintaro , Seki Minoru , Fukumura Kenichi 
Published: December 2004

AbstractThe reaction behavior of Saccharomyces formaosensis imobilized by polyacrylamide gel is presented. Two types of the immobilized yeast are studied, i. e. the immobilized resting yeast and the immobilized growing yeast. For both of the yeast, reaction retes are expressed by the Michaelis‐Menten type equation with a linear ethanol inhibition factor. The Michaelis constants aere close each other, but considerably larger that of native S. cerevisiae. Distribution of the growing yeast cell inside the carrier gel is presented. It is found that the cell density is somewhat higher near the surface of the carrier.
Preparation of immobilized α‐amylase covalently attached to granular polyacrylonitrile
Authors: Handa Takashi , Hirose Akira , Akino Toshiro , Watanabe Kosuke , Tsuchiya Haruo 
Published: December 2004

AbstractIn this report, α‐Amylase originating from Bacillus subtilis (liquefying type) was immobilized on partially imidoesterized polyacrylonitrile (PAN) by covalent bonding. For the preparation of immobilized α‐amylase, which has a high activity and high stability to repeated use, the optimum conditions for the preparation reaction were investigated. The optimum conditions for the preparation reaction were quantified on the basis of the enzymatic activity, the preservation of the activity during repeated use in batch process and the protein content on the support. Further‐more, enzymatic properties of immobilized α‐amylase prepared at optimum conditions were compared with the native enzyme. The optimum temperature and reaction time for the imidoes‐terification reaction were 30°c and 6 h, respectively, whereas those of the amidinatin reaction were 30–40°C and more than 3 h, respectively; the optimum pH range was 9–10. Immobilized α‐amylase prepared at the optimum conditions was very stable against the repeated use and had more than 90% of relative to activity of the first use after the tenth procedure. The initial reaction rate of immobilized α‐amylase was lower than native α‐amylase, but same amount of reducing sugars were produced after the reaction passed for more than 90 min. The immobilized α‐amylase was less stabel at the high temperature and the more basic media. However, after long incubation time, immobilized α‐amylase was more stable than the native enzyme in exposure to heat and a storng base.