bluuebunny/crossref_metadata_2025_split huggingface dataset:
Continuous proteolysis with a stabilized protease. II. Continuous experiments
Authors: Boudrant J. , Cheftel C. 
Published: December 2004

AbstractBatch proteolysis experiments were performed in order to choose a protein–protease system to prepare a correct hydrolysate suitable for the enrichment of soft‐drinks. The system eventually studied was casein–Alcalase.Comparative batch and continuous proteolysis of casein by Alcalase showed that the reaction, which does not exactly follow first order kinetics with respect to the substrate concentration, is inhibited by the reaction products. Furthermore, experiments were done in order to determine the reaction conditions (pH 8.8 in the reactor, casein concentration 5%, 40°C). Determining the molecular weight of Alcalase (43,000) suggested the choice of ultrafiltration membrane PM 30.Studies of continuous proteolysis with the chemically stabilized enzyme retained by the ultrafiltration reactor showed that protease reuse for seven days at 40°C is possible and that the growth of microorganisms is practically inhibited under these conditions. Gel chromatography showed the molecular weight range of the peptides to be less than 2,000. Triangular taste tests showed that the threshold identification concentration of the dry hydrolysate in orange juice is about 0.65%.
Modelling Xanthomonas campestris batch fermentations in a bubble column
Authors: Pons A. , Dussap C. G. , Gros J. B. 
Published: December 2004

AbstractRate and yield expressions relating to biomass and xanthan formation and to nitrogen, glucose, and oxygen consumption were established for Xanthomonas campestris batch fermentations in a bubble column. Microbial growth was described by the logistic rate equation, characterized by a maximum specific growth rate μM = 0.5 h−1 and a maximum attainable cell concentration provided by nitrogenous compounds. With regard to carbon metabolism, the decrease with time in experimental yields and in the experimental specific rates of xanthan production and glucose assimilation demonstrated the inadequacy of the Luedeking–Piret model. These decreases were connected to the simultaneous drop in dissolved‐oxygen tension observed during xanthan synthesis. The knowledge of metabolic pathways and energetic balance were used to establish the relationships between substrate utilization, ATP generation, and xanthan production. The model was structured by assuming the oxygen limitation of both the respiration rate and the efficiency of the oxidative phosphorylation mechanism (P/O ratio). Consequently, the specific rates and yield expressions became dependent on the dissolved‐oxygen tension, i.e., of the volumetric oxygen transfer in the fermentor.
Transient method for proposing the mechanisms of reactions over immobilized enzymes
Authors: Wu Jau‐Yann , Weng Hung‐Shan 
Published: December 2004

AbstractThe transient response method is introduced to elucidate the mechanism of reaction over immobilized enzyme. Glucose oxidation over the glucose oxidase that was immobilized on ion‐exchange resin using glutaraldehyde as a linking agent is selected as an example here. The transient responses of a fixed‐bed reactor to step increases and decreases in glucose, oxygen, and gluconolactone feed concentrations have been monitored and interpreted. From some responses, we have found that gluconolactone is formed in the reaction of glucose with adsorbed oxygen, while hydrogen peroxide is formed in the reaction of oxygen with adsorbed glucose. Combining all information from interpreting the responses with the literature, a mechanistic picture can be obtained as follows:

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An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the presence of Thiobacillus ferrooxidans
Authors: Pesic B. , Oliver D. J. , Wichlacz P. 
Published: December 2004

AbstractThe oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+ < 0.001M, T < 25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression:

Below pH = 2.2, the oxidation rate is independent of H+ Concentration.
Impossibility of coexistence of three pure and simple competitors in configurations of three interconnected chemostats
Authors: Chang Shiuan‐Wu , Baltzis B. C. 
Published: December 2004

AbstractIt is well established that pure and simple microbial competitors cannot coexist at a steady state if their environment is homogeneous. For the case of two microbial populations competing purely and simply in two interconnected chemostats having time‐invariant input(s), it is known from the literature that a stable steady state of coexistence arises in domains of the operating parameters space and is attributed to the spatial heterogeneities of the system, which allow a different species to have the competitive advantage in each one of the two sub‐environments. This article investigates whether the aforementioned result can be extended to the case of three species competing in three interconnected vessels. By studying all possible alternate configurations of the three‐chemostat system, it is shown that coexistence of the three species is impossible, except possibly for some discrete values of the operating parameters. Some potential explanations for the results are discussed.
Transient responses of hybridoma cells to nutrient additions in continuous culture: I. Glucose pulse and step changes
Authors: Miller William M. , Wilke Charles R. , Blanch Harvey W. 
Published: December 2004

AbstractGlucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady‐state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100–200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by‐product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day−1. The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.
Different modes of hydrocarbon uptake by two Pseudomonas species
Authors: Goswami Pranab , Singh H. Devendra 
Published: December 2004

AbstractThe mode of n‐hexadecane uptake by two organisms—Pseudomonas M 1 and Pseudomonas N 1—was studied. During the growth of Pseudomonas M 1 on n‐hexadecane, no extracellular biosurfactant/bioemulsifier was produced, no significant n‐hexadecane pseudosolubilization was observed, and the reduction of surface and interfacial tensions in the cell‐free culture broth was negligible. EDTA, a known inhibitor of hydrocarbon pseudosolubilization, did not inhibit the growth of the organism on n‐hexadecane. Normal hexadecane‐grown cells showed strong surface‐active properties and capacity to adhere firmly to hydrocarbon phase. It was concluded that in this organism, surface‐active properties of the cells facilitate attachment of cells to the hydrocarbon–water interface generated by agitation, and promote substrate uptake and growth; no hydrocarbon pseudosolubilization or extracellular mediator is involved in the substrate uptake. Pseudomonas N 1 grew on n‐hexadecane much faster than Pseudomonas M 1. Growth of this organism on n‐hexadecane was associated with the extracellular production of biosurfactant–bioemulsifier and n‐hexadecane pseudosolubilizing factor; the growth was strongly inhibited by 5 mM EDTA, indicating that hydrocarbon pseudosolubilization was the dominant factor in substrate uptake. The rate of n‐hexadecane pseudosolubilization was high enough to account for the substrate up take rate. Hydrocarbon emulsifying and n‐hexadecane pseudosolubilizing factors were isolated and tentatively characterized as lipoprotein and glycoprotein, respectively. Both factors act in a synergistic manner to provide enhanced hydrocarbon transport to cells through pseudosolubilization. It is proposed that this facility of mediated hydrocarbon transport is the basis for the relatively fast rate of growth of Pseudomonas N 1 on hydrocarbon.
Cellulase production by Trichoderma reesei when cultured on xylose‐based media supplemented with sorbose
Authors: Schaffner D. W. , Toledo R. T. 
Published: December 2004

AbstractThe ability of L‐sorbose to stimulate cellulase production In shake flask culture of Trichoderma reesei was examined in mineral salts media (initial pH 5.0) containing either 1.0% D‐xylose, 1.0% cellulose, and/or 0.1, 0.3, or 0.5% L‐sorbose. When sorbose was the only carbon source, growth was limited, little substrate was utilized, pH increased, and cellulase activity was not apparent. The other carbon sources promoted good growth, pH dropped sharply to 2.5–3.0, substrate was utilized rapidly, and cellulase activity was detected. After three weeks of fermentation, twice as much cellulase activity was detected in the medium containing only cellulose as the carbon source, as compared to xylose as the carbon source. Cellulase activity was higher when media contained xylose supplemented with sorbose compared to xylose as the only carbon source. At 0.3 and 0.5% levels of sorbose supplementation of xylose‐based media, cellulase activity was similar to that in cellulose‐based media.
An alternate method for estimation of cell growth kinetics from batch cultures
Authors: Lee Jeewon , Chang Hsiao‐Lung , Parulekar Satish J. , Hong Juan 
Published: December 2004

AbstractAn alternative to estimation of cell growth kinetics via continuous culture experiments is proposed in this article. The method employed is based on batch culture experiments with very small inocula (initial cell concentrations being typically less than 5000 cells/mL). Such low initial cell concentrations result in extended exponential cell growth phase during which culture conditions remain unchanged, thereby permitting precise estimation of specific cell growth rates from batch experiments especially for fast‐growing microorganisms such as Bacillus species. The effectiveness and utility of this approach are demonstrated via several experiments conducted with a wild‐type strain (Bacillus subtilis TN106) and a recombinant strain (B. subtilis TN106[pAT5]). True establishment of exponential growth phase requires insignificant variance of most of the culture conditions during the initial growth phase. Satisfaction of this requirement is demonstrated for microbial systems investigated here. This approach is especially well suited for recombinant microorganisms containing segregationally unstable plasmids, since estimation of growth kinetics of these from continuous cultures is very difficult and highly unreliable due to continual reversion of recombinant ceils to plasmid‐free host cells unless some selection pressure is applied at levels sufficient to keep the presence of plasmid‐free cells minimal.
Kinetic study of hybridoma cell growth in continuous culture. I. A model for non‐producing cells
Authors: Frame Kelly K. , Hu Wei‐Shou 
Published: December 2004

AbstractThe kinetic behavior of a nonproducing hybridoma clone AFP‐27‐NP was investigated in continuous culture under glucose‐limited conditions. A total of more than 21, 000 h of cultures were operated at dilution rates ranging from 0.01 to 0.06 h−1. The viable cell concentrations, dead cell concentrations, and cell volumes all varied with the dilution rate. A steady‐state model was developed based on the biomass concentration and the glucose concentration. The specific growth rate as a function of glucose concentration is described by a model similar to the Monod model with a threshold glucose concentration and a minimum specific growth rate incorporated; the model is meaningful only at glucose concentrations and specific growth rates above these levels. A death rate is included in the model which is described by an inverted Monod‐type function of glucose concentration. The yield coefficient based on glucose is constant in the lower range of specific growth rates and changes to a new constant value in the upper region of specific growth rates. No maintenance term for glucose consumption was needed; in the plot of specific glucose consumption rate vs. specific growth rate, the line intercepted the specific growth rate axis at a value close to the minimum growth rate. The values for the model parameters were determined from regression analysis of the steady‐state data. The model predictions and experimental results fit very well.
Some considerations for optimization of desorption chromatography
Authors: Gu Tingyue , Tsai Gow‐Jen , Tsao George T. 
Published: December 2004

AbstractThe effect of isotherm parameters of a displacer on the efficiency of desorption Chromatography has been investigated numerically. A general nonlinear multicomponent rate equation model with Langmuir isotherm was used in this study. It was found that the best displacer in this kind of operation is usually not the one that is more strongly adsorbed than the adsorbates when the operation is to displace and concentrate the adsorbates from a saturated or partially saturated column and to minimize the amount of displacer used. The desorption Chromatography is different from the classical displacement development in both operational purpose and the requirement for the displacer. The desorption Chromatography in industrial practice was also analyzed and discussed for the case in which the displacer is introduced in either the same or the reverse flow direction after an incomplete frontal adsorption operation.
Model of oxygen transport limitations in hollow fiber bioreactors
Authors: Piret James M. , Cooney Charles L. 
Published: December 2004

AbstractAxial and radial oxygen depletion are believed to be critical scale‐limiting factors in the design of cell culture hollow fiber bioreactors. A mathematical analysis of oxygen depletion has been performed in order to develop effectiveness factor plots to aid in the scaling of hollow fiber bioreactors with cells immobilized in the shell‐side. Considerations of the lumen mass transport resistances and the axial gradients were added to previous analyses of this immobilization geometry. An order of magnitude analysis was used to evaluate the impact of the shell‐side convective fluxes on the oxygen transport. A modified Thiele modulus and a lumen and membrane resistance factor have been derived from the model. Use of these terms in the effectiveness factor plots results in a considerable simplification of the presentation and use of the model. Design criteria such as fiber dimensions and spacing, reactor lengths, and recycle flow rates can be selected using these plots. Model predictions of the oxygen limitations were compared to experimental measurements of the axial cell distributions in a severely oxygen limited hollow fiber bioreactor. Despite considerable uncertainty in our parameters and nonidealities in hollow fiber geometry, the cell distribution correlated well with the modeling results.
Simultaneous saccharification and fermentation of cellulose to lactic acid
Authors: Abe Shin‐ichiro , Takagi Motoyoshi 
Published: December 2004

AbstractRecent interest in the industrial manufacture of ethanol and other organic chemicals from biomass has led to the utilization of surplus grain and cane juice as a fermentation feedstock. Since those starting materials are also foods, they are expensive. As an alternative, cellulosic substances—the most abundant renewable resources on earth1—have long been considered for conversion to readily utilizable hydrolyzates.2, 3For the production of ethanol from cellulose, we have proposed the simultaneous saccharification and fermentation (SSF) process.4 In SSF, enzymatic cellulose hydrolysis and glucose fermentation to ethanol by yeast proceed simultaneously within one vessel. The process advantages—reduced reactor volume and faster saccharification rates—have been confirmed by many researchers.5–8 During SSF, the faster saccharification rates result because the glucose product is immediately removed, considerably diminishing its inhibitory effect on the cellulase system.9To effectively apply the SSF method to produce substances fermented from glucose, several conditions should be satisfied. One is coincident enzymatic hydrolysis and fermentation conditions, such as pH and temperature. The other is that cellulase inhibition by the final product is less than that by glucose and/or cellobiose. One of us has reported that acetic acid, citric acid, itaconic acid, α‐ketoglutaric acid, lactic acid, and succinic acid scarcely inhibit cellulase.10 This suggests that if the microorganisms which produce these organic acids were compatible with cellulase reaction conditions, the organic acids could be produced efficiently from cellulosic substrates by SSF.In this article, the successful application of SSF to lactic acid production from cellulose is reported. Though there have been several reports of direct cellulose conversion to organic acids by anaerobes such as Clostridium, only trace amounts of lactic acid were detected in the fermentation medium among the low‐molecular‐weight fatty acid components.11–13 Lactic acid is one of the most important organic acids and has a wide range of food‐related and industrial applications.
Use of fluorometry for monitoring and control of a bioreactor
Authors: Li Jain‐Ke , Humphrey Arthur E. 
Published: December 2004

AbstractA new fluorescent bioreactor monitoring probe—multiple excitation fluorometric system (MEFS)—has been developed. This probe was compared to the commercially available BioChem Technology FluroMeasure system (NADH probe). In this task the fluorescence behavior of three model fermentation systems, ethanol fermentation by Candida utilis, phenol fermentation by Pseudomonas putida, and glucose fermentation by Saccharomyces cerevisiae, were examined. The results indicated that the fluorescence intensity and behavior of various cellular fluorophors vary significantly between the different fermentation systems. Monitoring a fermentation process using only NAD(P)H fluorescence provided limited information. The NAD(P)H fluorescence was found not to be the best fluorescence signal for monitoring cell concentrations. The best way of monitoring a bioreactor by fluorometry may be to monitor several fluorophors in the whole culture broth simultaneously and to relate these fluorescence signals to various biological parameters.
Optimization of batch processes involving simultaneous enzymatic and microbial reactions
Authors: Asenjo J. A. , Sun W.‐H. , Spencer J. L. 
Published: December 2004

AbstractTwo general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
Extractive fermentation for lactic acid production
Authors: Yabannavar V. M. , Wang D. I. C. 
Published: December 2004

AbstractLactic acid extractive fermentation was demonstrated using Alamine 336 in oleyl alcohol at acidic pH. The use of an efficient extraction system was possible through employment of the cell immobilization procedure. Process modeling was performed to relate the various process parameters such as flow rate, concentration, and pH. In experiments with 15% Alamine 336/oleyl alcohol, the bioreactor operation resulted in a higher productivity (12 g/L gel h) compared to that of a control fermentation (7 g/L gel h). Strategies for optimizing the extractive fermentation process were proposed considering both productivity and product recovery.
Optimization of L‐malic acid production by Aspergillus flavus in a stirred fermentor
Authors: Battat Emil , Peleg Yoav , Bercovitz Amir , Rokem J. Stefan , Goldberg Israel 
Published: December 2004

AbstractEffects of various nutritional and environmental factors on the accumulation of organic acids (mainly L‐malic acid) by the filamentous fungus Aspergillus flavus were studied in a 16‐L stirred fermentor. Improvement of the molar yield (moles acid produced per moles glucose consumed) of L‐malic acid was obtained mainly by increasing the agitation rate (to 350 rpm) and the Fez+ ion concentration (to 12 mg/L) and by lowering the nitrogen (to 271 mg/L) and phosphate concentrations (to 1.5 mM) in the medium. These changes resulted in molar yields for L‐malic acid and total C4 acids (L‐malic, succinic, and fumaric acids) of 128 and 155%, respectively. The high molar yields obtained (above 100%) are additional evidence for the operation of part of the reductive branch of the tricarboxylic acid cycle in L‐malic acid accumulation by A. flavus. The fermentation conditions developed using the above mentioned factors and 9% CaCO3 in the medium resulted in a high concentration (113 g/L L‐malic acid from 120 g/L glucose utilized) and a high overall productivity (0.59 g/L h) of L‐malic acid. These changes in acid accumulation coincide with increases in the activities of NAD+‐malate dehydrogenase, fumarase, and citrate synthase.