bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inner filter effects and their interferences in the interpretation of culture fluorescence
Authors: Srinivas S. P. , Mutharasan R. 
Published: December 2004

AbstractInner filter effects and their interferences in the measurement and interpretation of culture fluorescence are discussed. An approximate light intensity model for a typical open‐ended culture fluorescence measuring device is developed for calculating the fluorescence response of a component of interest in a general three component solution. The model is tested using well de fined synthetic fluorescent systems. The model is then extended for correlating culture fluorescence with cell density and metabolic state of microbial cultures based on a lumping approximation. The extended model has been utilized to derive culture fluorescence parameters of yeast culture at three distinct metabolic states.
Production and application of methylotrophic yeast Pichia pastoris
Authors: Duff Sheldon J. B. , Murray William D. 
Published: December 2004

AbstractPichia pastoris is a methylotrophic yeast that makes use bf the enzyme alcohol oxidase to catalyze the first step of the dissimilatory pathway that enables it to grow on methanol. Because of its stability and low substrate specificity, alcohol oxidase is of considerable interest for a range of biotechnological processes. Various feeding regimes were evaluated in an effort to increase the biomass concentration and productivity that could be achieved from fermentations using this organism. Through continuous or semicontinuous feeding, biomass concentrations were increased 10‐fold over those achieved in batch fermentations. In subsequent trials, nongrowing whole cells were applied successfully to convert ethanol to acetaldehyde. Quantitative conversions of 20‐g/L solutions of ethanol have been achieved in 2 h, and acetaldehyde concentrations of up to 35 g/L have been achieved using extended reaction times of 5 h. The conversion reaction was limited by end product inhibition and by acetaldehyde holdup within the yeast cells.
Kinetics of microbial growth on mixtures of pentachlorophenol and chlorinated aromatic compounds
Authors: Klec̆ka Gary M. , Maier Walter J. 
Published: December 2004

AbstractBatch experiments were conducted to examine the effects of several substrate analogs on the degradation of pentachlorophenol by an enrichment culture of pentachlorophenol‐utilizing bacteria. The presence of substrate analogs which were unable to serve as a carbon source for growth of the culture (e.g., 3,5,6,‐trichloro‐2‐pyridinol, 2,4‐dichlorophenoxyacetic acid) decreased the rate of pentachlorophenol degradation. The presence of a utilizable substrate analog (e.g., phenol, 2,4,5‐trichlorophenol) also inhibited the initial rate of pentachlorophenol degradation; however, the overall removal rate was accelerated due to an increase in cell mass concentration as a result of simultaneous growth on both substrates. These effects were shown to be predicted by a mathematical model based on a modified Monod equation. Kinetic parameters obtained from the results of laboratory studies can be used for further process analysis to define the optimal conditions for the biological treatment of complex mixtures of phenolic compounds.
Kinetics of bilirubin oxidase and modeling of an immobilized bilirubin oxidase reactor for bilirubin detoxification
Authors: Million Claudy J. P. , Klibanov Alexander M. , Langer Robert 
Published: December 2004

AbstractThe unbound bilirubin concentration and the enzymatic rate of bilirubin degradation by bilirubin oxidase in bilirubin‐serum albumin solutions have been investigated experimentally and theoretically. A stoichiometric bilirubin‐serum albumin binding analysis shows that the unbound bilirubin concentration depends only on the molar ratio of the total bilirubin concentration to the total serum albumin concentration. From the theoretical analysis and the measured unbound bilirubin concentrations, serum albumin may be modelled as a molecule having two binding sites, primary and secondary, with stoichiometric equilibrium constants of K1 = 6 × 107M−1 and K2 = 4.5 × 106M−1, respectively. The rate of total bilirubin degradation in bilirubin‐serum albumin mixtures is zero order. An immobilized bilirubin oxidase reactor model, which shows good agreement with experimental bilirubin conversions, is presented. At a flow rate of 1 mL/min with a 8‐mL reactor volume, a 50% bilirubin conversion per pass was observed with an inlet bilirubin concentration of 350μM and a serum albumin concentration of 500μM.
Experimental simulation of oxygen profiles and their influence on baker's yeast production: II. Two‐fermentor system
Authors: Sweere A. P. J. , Janse L. , Luyben K. Ch. A. M. , Kossen N. W. F. 
Published: December 2004

AbstractA reactor configuration consisting of two reactors with an exchange flow was used for the experimental simulation of large‐scale conditions. The influence of fluctuations in oxygen concentration on the growth and metabolite production of baker's yeast was investigated by sparging one fermentor with air and one with nitrogen gas. It was found that the biomass yield decreased and the metabolite formation increased with rising circulation time (longer oxygen‐unlimited and oxygen‐limited periods). Not only was the performance of the oxygen‐limited fermentor characterised by (partly) reductive metabolism, but that of the oxygen‐unlimited fermentor as well. The results of the experiments in this reactor system were compared with those from the experiments carried out in a one‐fermentor system with periodically changing oxygen concentrations. The formation of acetic acid, which is characteristic for transient states, showed a distinct difference between the two reactor systems.
Semicontinuous diffusion fermentation of fodder beets for fuel ethanol and cubed protein feed production
Authors: Gibbons William R. , Westby Carl A. , Arnold Eugene 
Published: December 2004

AbstractA novel, semicontinuous diffusion fermentation system was used to produce fuel ethanol and a cubed protein feed (CPF) from fodder beets at an intermediate scale. In the process, fodder beet cubes were augered diagonally upward against a flow of 0.26N H2SO4 and yeast in a tubular fermentor. Exiting one end of the fermentor was CPF, while fermented beer [6–9% (v/v) ethanol] exited the other end. Retention times for beer and CPF were 264 and 72 h, respectively. Contamination was controlled by maintaining the fermentation pH between 2.1 and 2.6 using H2SO4. Production costs for a greatly scaled‐up (times 1400) conceptual version of this system (using a continuous rather than a semicontinuous processing mode) were projected by calculation to be $0.529/L for 95% ethanol (net of a $0.112/L credit for CPF). The calculated energy balance (energy output‐energy input ratio) was estimated to be 3.04. In calculating the energy balance, the output energy of the CPF and input energy for growing the fodder beets were not included. A design for the scaled‐up plant is provided.
Study of fermentation behavior and formulation of a semidefined nutrient medium based on acid‐production measurements in Z. mobilis cultures
Authors: Veeramallu Uday , Agrawal Pramod 
Published: December 2004

AbstractBatch fermentations of glucose to ethanol by Z. Mobilis.(ATCC 10988) were examined in several semidefined nutrient media. The measurement of acid produced by the microorganism was used to study its transient fermentation characteristics. Limitation of nitrogen source in the semidefined medium of Rogers and coworkers2 was found to limit the growth of this microorganism in the late stages of batch fermentations, when the initial glucose concentration was 75 g/L and higher. The microorganism exhibits a preference for inorganic nitrogen over preformed organic nitrogen provided by yeast extract. The microbial growth occurs exponentially in the presence of ammonium sulfate and yeast extract. However, in the absence of ammonium sulfate, the growth occurs in a linear fashion. The “linear” growth phase is characterized by poor cell‐mass yields, and during this phase, growth and ethanol production are decoupled. An improved semi‐defined growth medium is established which supports better growth rate and cellular yield, without affecting the ethanol yield.
Characteristic reaction paths of biochemical reaction systems with time scale separation
Authors: Liao James C. , Lightfoot Edwin N. 
Published: December 2004

AbstractA technique has been developed for characterizing the in vivo behavior of key enzymes from intermediate measurements. The technique is based on the identification of characteristic reaction paths, and it depends on the time scale separation characteristics of the systems. It is shown that useful information can be obtained from the phase plots of properly selected intermediate pairs or combinations which typically show process insensitive algebraic relations approached on time scales short compared to those of most practical interest. These characteristic reaction paths provide useful global measures of enzyme activity. The mathematical basis of reaction path analysis is investigated using linear transformation techniques. General theorems are developed predicting the existence of characteristic reaction paths as asymptotic limits whenever there is effective time scale separation. These limits are reached when fast reactions are relaxed, and available evidence suggests that these conditions will occur for the majority of reaction networks.
Application of characteristic reaction paths: Rate‐limiting capability of phosphofructokinase in yeast fermentation
Authors: Liao J. C. , Lightfoot E. N. , Jolly S. O. , Jacobson G. K. 
Published: December 2004

AbstractThe intracellular rate‐limiting capability of phosphofructokinase in baker's yeast (Saccharomyces cerevisiae) fermentation is investigated using the reaction path analysis discussed by Liao and Lightfoot in a previous article. It is found that the yeast cells under our experimental conditions indeed exhibit the characteristic behavior, and the characteristic reaction path on the G6P‐ATP phase plot is determined for cells fed with different sugars, cells of different strains, and cells in the transition period following rehydration. Results suggest that phosphofructokinase does not limit the CO2 production rate of the cells under investigation. However, it is not present in a great excess either: ca. 80% of phosphofructokinase activity is utilized by the glycolytic pathway of the cell under investigation.
Simultaneous measurements of oxygen diffusion coefficients and solubilities in fermentation media with polarographic oxygen electrodes
Authors: Ju Lu‐Kwang , Ho Chester S. , Baddour Raymond F. 
Published: December 2004

AbstractA membrane‐covered oxygen electrode was used to measure oxygen diffusion coefficients and solubilities in aqueous glucose solutions and various fermentation media following a newly developed methodology. The fermentation media studied were tryptic soy broth and those for fermentations of Penicillium chrysogenum, Saccharomyces cerevisiae, and Micrococcus glutamicus. The experimental results of oxygen diffusion coefficients and solubilities in glucose solutions were in good accord with the literature data. As for the fermentation media, both oxygen diffusion coefficients and solubilities were found to decrease with an increased fractional composition of these media, and log‐additive behaviors of the oxygen diffusion coefficients and solubilities in fermentation media were observed.
Controlling fermentation of lignocellulose hydrolysates in a continuous hollow‐fiber reactor using biosensors
Authors: Mandenius Carl Fredrik 
Published: December 2004

AbstractFermentation of lignocellulose hydrolysates as spent sulfite liquor or as hydrolysate from sulfur‐dioxide‐treated wood to ethanol has been controlled by using biosensors for glucose and ethanol. Yield and productivity were studied with respect to concentration level of the metabolites in a continuous hollow‐fiber reactor. High constant yield was achieved by controlling the glucose to low concentration levels. Reduced productivity were obtained when fermenting at high ethanol concentrations as an effect of inhibition of the yeast cells. The observations emphasize the advantage of controlling the process to favorable concentrations of monosaccharides and ethanol.
Optimization of microalgal production in a shallow outdoor flume
Authors: Laws Edward A. , Taguchi Satoru , Hirata Janice , Pang Lance 
Published: December 2004

AbstractThe marine diatom Cyclotella cryptica was grown over a period of 13 months in a 48‐m2 shallow outdoor flume. The use of foil arrays at intervals of 1.2 m to effect systematic vertical mixing in the flume was found to significantly enhance microalgal production (p = 0.006). Average photosynthetic efficiencies (based on visible irradiance) with and without the foil arrays in place were 9.6 ± 0.8 and 7.5 ± 0.5% (±95% confidence intervals), respectively. A cost–benefit analysis indicated that the foil arrays were cost‐effective if the value of the algae exceeded about $2.28 kg1 of ash‐free dry weight (AFDW). Parallel experiments performed in four 9.2‐m2 flumes showed that production was maximized when the cells were grown on a 2‐day batch cycle between harvests rather than on a 1‐ or 3‐day batch cycle. The optimum initial concentration (immediately after harvesting) of the algae was negatively correlated with the time interval between harvests and ranged from approximately 39 g AFDW/m3 on a 3‐day cycle to 213 g AFDW/m3 on a 1‐day cycle. The increase in production resulting from growth on a 2‐day rather than a 1‐day batch cycle was about 19% and was statistically significant at p = 0.0003. Growth of C. cryptica over a total period of 122 days during the 13‐month study in the 48‐m2 flume under near‐optimal conditions (2‐day batch cycle, initial concentration 155 g AFDW/m3) resulted in an average production rate (±95% confidence interval) of 29.7 ± 2.7 g AFDW/m2 d.
Limited modifications of soya proteins by immobilized subtilisin: Comparison of products from different reactor types
Authors: Herbert A. B. , Dunnill P. 
Published: December 2004

AbstractA comparison of different immobilized enzyme reactors has been made for the limited modification of soya storage proteins and the products compared with those from action of the soluble enzyme. Clarified total water extracts of soya protein were subjected to the action of subtilisin in a soluble and immobilized form. The sodium dodecyl sulfate (SDS) electrophoresis patterns of soya proteins modified by enzyme in the two forms differed for unbuffered soya protein at the same pH of 8.0. However, identical patterns could be obtained by a downward adjustment of the pH of soya protein treated with immobilized enzyme. The same SDS electrophoresis pattern could be obtained for a packed column of immobilized enzyme and a well‐mixed vessel by buffering. Operation of the column reactor at higher superficial linear velocities (above 1.47 cm/min), higher protein concentrations (8.8% w/v), and prolonged periods (24 h) led to a bed compression attributed to the protein coating of the support.
A batch reactor mass transfer kinetic model for immobilized biomass biosorption
Authors: Tsezos M. , Noh S. H. , Baird M. H. I. 
Published: December 2004

AbstractInactive cells of Rhizopus arrhizus have been immobilized into the form of particles of desirable particle size using a proprietary immobilization technique. The immobilized biomass particles are porous and are members of a new generation of biological origin adsorbents. The uranium adsorptive behavior of the biosorbent particles was modeled using a batch reactor mass transfer kinetic model of the biosorption process. The model successfully predicts the batch reactor adsorbate (uranium) concentration profiles and has provided significant insights on the way biosorbents function.
Operation of a three‐phase biofilm fluidized sand bed reactor for aerobic wastewater treatment
Authors: Ryhiner G. , Petrozzi S. , Dunn I. J. 
Published: December 2004

AbstractA biofilm fluidized sand bed column reactor (14 L) has been operated in the three‐phase mode on a soluble glucose‐yeast hydrolysate substrate in which the biofilm‐sand phase (1‐2.5 L) was suspended by direct aeration of the bed. Within two weeks a tight biofilm was formed whose activity resulted in a 90% reduction, with loads of 10.7 kg TC/m3day. The residence time was 1 h. The biofilm remained intact during operation with high residence times (up to 23 h) over three weeks. Oxygen transfer coefficients varied with aeration rate and sand quantity between 0.02 and 0.04 s−1 during non growth conditions; they decreased with increasing amounts of clean sand and were higher and relatively independent of the sand fraction with biofilm‐covered sand. Aeration rates used in the 14 L reactor were 23‐40 L/min (2.4‐4.1 cm/s) and were sufficient to suspend 78‐92% f the biofilm‐covered sand. Clean sand was 50‐75% suspended. Oxygen uptake rates varied between 15.4 and 23.1 mol/m3 h.
The use of image analysis for morphological measurements on filamentous microorganisms
Authors: Adams H. L. , Thomas C. R. 
Published: December 2004

AbstractCharacterization of mycelial morphology is important for the design and operation of filamentous fermentations. Initial investigations have been made of semiautomated image analysis as a replacement for a digitizing‐table method. It was shown that the image analysis method was more precise than the digitizing‐table method used, although this extra precision is unimportant in this application. On average, image analysis gave mean hyphal lengths 6% greater than digitizing, because the latter used chord lengths to represent are lengths. For short branches image analysis was less accurate. In time and convenience the image analysis method had an overwhelming advantage, and this advantage might be enhanced by full automation. The resulting ability to characterize mycelial morphology rapidly would permit such characterization to be used routinely in studies of filamentous fermentations.
A stirred bath technique for diffusivity measurements in cell matrices
Authors: Chresand Thomas J. , Dale Bruce E. , Hanson Shari L. , Gillies Robert J. 
Published: December 2004

AbstractA stirred bath technique was developed for determining effective diffusivities in cell matrices. The technique involves cell immobilization in a dilute gel which has negligible effect on solute diffusion. Agar and collagen were tested as immobilizing gels. Agar gel was shown to have minor interactions with the diffusion of various biological molecules, and was used for immobilization of Ehrlich Ascites Tumor (EAT) cells. Diffusivities of glucose and lactic acid were measured in EAT matrices for cell loadings between 20 and 45 vol %. Treatment with glutaraldehyde was effective in quenching the metabolic activity of the cells while preserving their physical properties and diffusive resistance. The measured data agree favorably with predictions based on Maxwell's equation for effective diffusion in a periodic composite material. The stirred bath technique is useful for diffusivity determinations in immobilized matrices or free slurries, and is applicable to both microbial and mammalian cell systems.
Centrifugal dewatering of acid casein curd: Effect of casein manufacturing and centrifugation variables on curd compression in a laboratory centrifuge
Authors: Munro P. A. , Van Til H. J. 
Published: December 2004

AbstractData relevant to curd compression in a horizontal, solid bowl decanter centrifuge have been obtained by studying the dewatering of acid casein curd in a batch laboratory centrifuge. Analysis of curd compression under centrifugal force predicts a moisture content gradient in the dewatered curd from a maximum at the curd–liquid interface to a minimum at the centrifuge bowl wall. This moisture content gradient was also measured experimentally, and its practical implications are discussed. Increases in centrifugal force, centrifugation time, and centrifugation temperature all caused a marked de crease in dewatered curd moisture content, whereas in creases in precipitation pH and maximum washing temperature caused a smaller decrease in dewatered curd moisture content.
Bacterial deposition on and detachment from surfaces in turbulent flow
Authors: Hermanowicz S. W. , Danielson R. E. , Cooper R. C. 
Published: December 2004

AbstractA number of experimental studies on deposition and detachment of bacterial cells of Pseudomonas sp. was performed in an inclined plate apparatus 2.3 m long. In each run, ca. 108cells were introduced into a layer of flowing water at Reynolds numbers of ca. 1000 and 1300. After a preset time, the flow was stopped and the position of attached cells measured. Spatial pattern of attached cells was initially aggregative and remained so for lower flow rates. For higher flow rates the pattern tended towards randomness, perhaps as a result of cell detachment. Overall sticking efficiency of cells was very small (ca. 10−5).
Dynamics of foreign protein secretion from Saccharomyces cerevisiae
Authors: Park Seujeung , Ramirez W. Fred 
Published: December 2004

AbstractA mathematical model describing the dynamics of foreign protein secretion from yeast cells is developed. The secretion events, which are a series of complicated enzymatic reactions and carrier‐involved transport, are lumped to a practically applicable model structure, based on the major interactions between the heterologous polypeptides and the host cell's secretory machinery through the pathway. The developed model structure predicts that the secretion rate constant is represented as a saturated form with respect to the host cell's specific growth rate. The validity of the proposed model structure is tested by generating dynamic response data to a step input of cycloheximide. The model system used in the experiment is SEY2102‐s21, which has an integrated copy of a yeast secretion‐mutant invertase that simulates well typical gene cassettes designed to secrete mature foreign proteins utilizing the yeast cell's secretion signals. Protein quantification is done by gel electrophoresis followed by immuno‐blot on nitrocellulose filters and subsequent scanning with a reflectance densitometer. Experimental data confirm the proposed model structure.
Modeling of contact‐inhibited animal cell growth on flat surfaces and spheres
Authors: Cherry Robert S. , Papoutsakis Eleftherios Terry 
Published: December 2004

AbstractA model of contact‐inhibited growth of cells on flat and spherical surfaces is presented. It shows that contact inhibition does not significantly affect the calculated growth rate of cells unless they are allowed to multiply a large amount from the original seeding density. Microcarriers seeded at low densities require long times to reach confluence because contact inhibition becomes important. In systems with both growth and separate cell death, the equilibrium fraction of holes in the confluent monolayer is below 8% if the death rate is less than half the growth rate, but increases rapidly as the death rate increases from that value.