bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanistic analysis of complex enzyme deactivations: Influence of various parameters on series‐type inactivations
Authors: Sadana Ajit , Henley James P. 
Published: May 2005

AbstractA series‐type enzyme deactivation model is used to model and to quantitate some more complex enzyme deacti‐vations. The influence of temperature, pH, immobilization, chemical modifier (inhibitor or protector), substrate, and metal ion on the inactivation kinetics and on the parameter values is examined. In some cases the influence of two parameters on enzyme inactivations is presented. This provides further physical insights into enzyme inactivation and stabilization processes.
Investigations of oxygen transfer into Penicillium chrysogenum pellets by microprobe measurements
Authors: Wittier Rüdiger , Baumgartl Horst , Lübbers Dietrich Werner , Schügerl Karl 
Published: May 2005

AbstractA microcoaxial needle sensor with a tip diameter of ca. 0.7 μm was used as a microprobe to measure profiles of dissolved oxygen tension (DOT) within fixed pellets of Penicillium chrysogenum as a function of the DOT level around the pellet, in the presence and absence of bulk convective flow and turbulence. The investigations indicate that the oxygen transfer mechanism is complex. The results were interpreted by assuming the penetration convective flow into the entire pellet and penetration of turbulence into the outer range. A model was developed which was able to describe the measured DOT profiles very well. The model takes into account molecular and turbulent diffusion as well as convective flow as transfer mechanisms inside of the pellet. Structures of pellets used for microprobe measurements were evaluated by histological investigations. Considerable variations of mycelial density with radius within the pellets were found.
Thin‐film antimony–antimony‐oxide enzyme electrode for penicillin determination
Authors: Flanagan M. T. , Carroll N. J. 
Published: May 2005

AbstractA potentiometric penicillinase electrode is reported in which the base pH transducer is a thin‐film anti‐mony–antimony‐oxide electrode deposited by vacuum evaporation. Several enzyme immobilization procedures have been examined and a crosslinked protein film found to be the most appropriate to this type of sensor. The use of an adjacent antimony–antimony‐oxide track as a pseudoreference electrode was successfully demonstrated. The overall response was shown to be independent of the stirring rate above 100 rpm, but the kinetics of the response were found to depend markedly on the stirring rate. The intrinsic linear response range was 3 × 10−4Mto 7 × 10−3M penicillin G. Linearizing transforms that extend the useful range were examined.
Effect of pH oscillations on a competing mixed culture
Authors: Davison Brian H. , Stephanopoulos Gregory 
Published: May 2005

AbstractTwo microorganisms, E. coli and S. cerevisiae, competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a Chemostat. Pure culture experiments found S. cerevisiae to be insensitive to pH between 5 and 4.3 with a maximum specific growth rate (μmax) of 0.4/hr; while μmax of E. coli decreased from 0.6 h−1 at pH 5 to 0.1 h−1 at pH 4.3. Steady‐state and cross‐inoculation chemostat runs at a dilution rate of 0.17 h−1 confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D =0.17 h−1 with 1 g per liter glucose feed. The 16 h/16 h cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 h pH 5/14 h pH 4.3 cycle was found to be stable with smaller yeast concentrations. A 6 h/6 h cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus, varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.
Characteristics of lipase‐catalyzed hydrolysis of olive oil in AOT–isooctane reversed micelles
Authors: Han Daeseok , Rhee Joon Shick 
Published: May 2005

AbstractCandida rugosa lipase solubilized in organic solvents in the presence of both surfactant and water could catalyze the hydrolysis of triglycerides, and kinetic analysis of the lipase‐catalyzed reaction was found to be possible in this system. Among eight organic solvents tested, isooctane was most effective for the hydrolysis of olive oil in reversed micelles. Temperature effect, pH profile, Km,app and Vmax,app were determined. Among various chemical compounds, Cu2+, Hg2+, and Fe3+ inhibited lipase severely. But the enzyme activity was restorable partially by adding histidine or glycine to the system containing these metal ions. The enzyme activity was dependent on R (molar ratio of water to surfactant) and maximum activity was obtained at R = 10.5. Upon addition of glycerol to the reversed micelles, lipase activity was affected in a different fashion depending on the R values. Stability of the lipase in reversed micelles was also dependent on R, and it was most stable at R = 5.5.
Biohydrogenation of unsaturated fatty acids by a mixed culture of rumen microorganisms
Authors: Kellens M. J. , Goderis H. L. , Tobback P. P. 
Published: May 2005

AbstractThe biohydrogenation of C‐18 unsaturated fatty acids was examined in a mixed culture of microorganisms prepared by inoculating a proper growth medium with a sample of rumen fluid. Some major factors influencing the hydrogenation capacity have been investigated. The age of the mixed culture, the type of inoculum used, the concentration of substrates as well as the presence of sterile rumen fluid in the growth medium were found to be important factors determining biohydrogenation behavior. It could be shown that the mixed microbial culture, which had been grown for about 24 h on a medium similar to that of Bryant and Robinson, contained sterile rumen fluid (10% v/v), and had been inoculated with a sample of the whole untreated rumen content, had the best biohydrogenation capacity. The culture was able to carry out the complete conversion of linoleic and linolenic acid to stearic acid.
Stabilization of κ‐carrageenan gel with polymeric amines: Use of immobilized cells as biocatalysts at elevated temperatures
Authors: Chao K. C. , Haugen M. M. , Royer G. P. 
Published: May 2005

AbstractSpherical beads of κ‐carrageenan containing entrapped cells were prepared in a two‐step process. First, the beads were formed by dispersing a warm carrageenan cell suspension into stirring oil. After cooling (gelation) the beads were cured by treatment with amines. Ten amines of various sizes and structures were tested. We evaluated the mechanical strength and the applicability of aminetreated gels as immobilization matrices. The results of critical compression tests indicate that linear and branched polyethylenimines (PEI) are both good curing agents. PEI treated carrageenan beads also exhibited superior resistance to heat and abrasion. Furthermore, PEI polymers were demonstrated to be effective in stabilizing the lactase activity of the free and immobilized Bacillus stearothermophilus cells. The immobilized cell preparations of Saccharomyces cerevisiae, B. stearothermophilus, and Flavobacterium sp. were treated with branched PEI and evaluated for the activity of invertase (EC 3.2.1.26), lactase (EC 3.2.1.23), and glucose isomerase (EC 5.3.1.18), respectively, in a packed bed reactor at 60°C. The apparent half‐lives were 108, 39, and 64 days, respectively.
Measurement of interfacial areas in aerobic fermentations by ultrasonic pulse transmission
Authors: Stravs Andrej A. , Pittet Alain , von Stockar Urs , Reilly Peter J. 
Published: May 2005

AbstractThe penetration of ultrasonic waves through opaque media and the large difference in the acoustic properties between air bubbles and the fermentation broth were used to measure the energy attenuation of pulsed ultrasound by the bubbles as the waves passed through the broth. This leads to an on‐line determination of the specific interfacial area provided information is available about the holdup or bubble mean diameter. This article gives the principle of the method and demonstrates how the measured interfacial area may be used in evaluating the mass transfer coefficient of a fermentation system in a bubble column.
Coimmobilization of substrate and biocatalyst: A method for bioconversion of poorly soluble substances in water milieu
Authors: Kaul Rajni , Adlercreutz Patrick , Mattiasson Bo 
Published: May 2005

AbstractCoimmobilization of biocatalyst and substrate was studied as a method to increase the conversion rate in systems with substrates of extremely low solubility in water. The system studied was the conversion of hydrocortisone to prednisolone by Arthrobacter simplex. As a matrix for coimmobilization, alginate turned out to be superior to agar and agarose. After the reaction was complete, the beads were solubilized, andthe cells recovered for reuse, by centrifugation, whereas the prednisolone was extracted from the supernatant.
An investigation of the efficacy of biological additives for the suppression of pyritic sulphur during simulated froth flotation of coal
Authors: Stainthorpe A. C. 
Published: May 2005

AbstractThe biological molecule responsible for the suppression of pyritic sulfur in fine coal simulated froth flotation treated with bacteria was identified. Protein was found to be the most effective agent in pyrite suppression of the three cell components (protein, lipid, and carbohydrate) assayed. Coal recovery and ash removal of the flotation process were only slightly reduced by this treatment. Other protein‐containing materials were evaluated for their ability to suppress pyrite flotation. Whey was found to be the most cost‐effective flotation additive of those assayed. The sulfur content of the whey‐treated float was reduced by 84.0% in a synthetically prepared fractionated coal (10.7% sulfur), by a raw whey dosage of 20 μL/g coal. The inorganic sulfur component of a natural high sulfur coal fraction (10.9%) was completely depressed by this whey addition. The effect of particle size and pulp density upon the process were investigated.
Osmotic, biomass, and oxygen effects on the growth rate of Fusarium oxysporum using a dissolved‐oxygen‐controlled turbidostat
Authors: de la Broise Denis , Durand Alain 
Published: May 2005

AbstractThe system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady‐state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus, Fusarium oxysporum 47 isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to ‐25 bars. Increasing biomass concentration in the range 0.1‐1.0 g/L appears to depress markedly the maximum growth rate.
Effect of environmental growth conditions on plasmid stability, plasmid copy number, and catechol 2,3‐dioxygenase activity in free and immobilized Escherichia coli cells
Authors: Sayadi S. , Nasri M. , Barbotin J. N. , Thomas D. 
Published: May 2005

AbstractIn order to better understand the high plasmid stability in immobilized recombinant E. coli cells, the effects of dilution rate on the pTG201 plasmid stability, the copy number, and the catechol 2,3‐dioxygenase (encoded by XyIE gene) production were, at first, studied in free E. coli W3101 continuous cultures in minimal media. It was found that decreasing specific growth rate increased the plasmid copy number and the catechol 2,3‐dioxygenase activity but the stability decreased. In continuous culture with immobilized cells, an increase was shown in plasmid copy number and catechol 2,3‐dioxygenase activity probably due to the distribution of growth in the gel beads. Besides mechanical properties of gel beads which may allow limited cell divisions, the increase in plasmid copy number is involved in enhanced plasmid stability in immobilized cells. In the same way, an experiment conducted in LB medium dealing with competition between pTG201‐free and pTG201‐containing E. coli B cells was described. It was shown that the competition was not more pronounced in gel bead compared to a free system. The effects of nutritional limitations on pTG201 plasmid stability and catechol 2,3‐dioxygenase activity during chemostat cultivations in free and immobilized E. coli B cells were also investigated. It was found that immobilization of cells increased the stability of pTG201 even under glucose, nitrogen, or phosphate limited cultures. However in the case of magnesium depleted culture, pTG201 was shown to be relatively instable and a decrease in viable cell number during the immobilized continuous culture was observed. By contrast to the free system, the catechol 2,3‐dioxygenase activity increased in immobilized cells under all culture conditions used.
Destruction and formation of toxins by one bacterial species affect biodegradation by a second species
Authors: Murakami Yoshitaka , Alexander M. 
Published: May 2005

AbstractTwo strains of Pseudomonas able to grow on phenol or p‐nitrophenol (PNP) were isolated from sewage. Pseudomonas sp. PN101 mineralized and formed nitrite from PNP but did not mineralize phenol, and Pseudomonas sp. PH111 mineralized phenol but not PNP. Phenol increased the lag period before Pseudomonas sp. PN101 grew on and mineralized PNP, but this toxicity was reduced by inoculation of the medium with Pseudomonas sp. PH111. PNP inhibited growth of Pseudomonas sp. PH111 and slightly increased the length of the acclimation period for the mineralization of phenol by the bacterium. Inoculation of Pseudomonas sp. PN101 into solutions containing PNP and phenol increased the lag period prior to growth of Pseudomonas sp. PH111 on phenol and markedly lengthened the lag period for its mineralization of phenol. Coinciding with this delay in the onset of phenol degradation was the accumulation of an organic compound formed from PNP by Pseudomonas sp. PN101. This compound was not mineralized by the phenol‐degrading bacterium. The data suggest that bacteria may interact during the decomposition of chemical mixtures by destroying or by forming toxins that affect the biodegradation of individual components of those mixtures.
Performance of a membrane reactor for cellobiose hydrolysis
Authors: Pizzichini M. , Fabiani C. , Adami A. , Cavazzoni V. 
Published: May 2005

AbstractA continuous enzymatic hollow fiber reactor (HFR), obtained by immobilizing cellobiose active cells into the shell side of hollow‐fiber modules, was studied. The HFR yield was monitored by glucose analysis resulting from hydrolysis of cellobiose. The residence time of substrate in the bioreactor to obtain convenient hydrolysis yields was calculated from tests carried out by varying the reactor dilution rate in the range 0.001–0.004 L/min. The glucose yield was measured for 300 h (continuous substrate flux). The yield decreased from 40 to 15%. This decrease was due to the loss of specific activity in the operating conditions and to the pressure drop increase from 0.2 to 1.7 atm. The pressure drop increase is in turn dependent on the cell loading (0.2–2.1 g dry cell) and the substrate flux.
α‐Factor directed expression of the human epidermal growth factor in Saccharomyces cerevisiae
Authors: Coppella Steven J. , Dhurjati Prasad 
Published: May 2005

AbstractExpression kinetics of the human Epidermal Growth Factor (hEGF) from the α‐factor prepro region in a 2‐μm based plasmid was studied in Saccharomyces cerevisiae. Production of hEGF was highly medium de pendent as a chemically defined, nonenriched media had a significantly lower yield than did enriched media. Also cells grown on yeast nitrogen base without amino acids with casamino acids degraded the hEGF after cell growth as opposed to a yeast extract, peptone, and dextrose (YEPD) medium, which elicited no measurable extracellular proteolysis of the hEGF. α‐factor directed production kinetics of hEGF on the YEPD medium were growth associated, secretion limitations and extracellular degradation were negligible, and the hEGF was nearly 100% selectively secreted. With sufficient agitation, shake flask experiments were representative of aerated controlled batch fermentations. No effect of high cell density was observed on cell growth or hEGF production kinetics. The hollow fiber bioreactor had no direct effect on the substrate or protein yields of S. cerevisiae, however the low oxygen transfer capacity of the membrane was not sufficient to support respiration.
Transient kinetics of hybridoma growth and monoclonal antibody production in serum‐limited cultures
Authors: Dalili Mina , Ollis David F. 
Published: May 2005

AbstractA quantitative study of the influence of initial serum concentration on hybridoma growth rate, maximum viable and total cell yield, and specific antibody production rate is presented. The specific growth rate varied in a Monod fashion with initial serum levels (2–10% FCS), giving Km = 1.6 v/v% and μmax = 0.92 d−1. The maximum cell yields (total and viable) were linear with initial serum level, indicating stoichiometric as well as kinetic limitation by serum component(s). The specific antibody production rate for each individual run fitted well to a non‐growth‐associated model. However, the non‐growth‐associated parameter varied monotonically with initial serum concentration, suggesting the catalytic role of serum component(s) in antibody production. Also, glutamine was utilized inefficiently, with at least a third of it secreted back into the culture supernate in the form of glutamate. While very simple model equations describe the specific growth and product formation rate for an individual batch run, the larger picture indicates need for a more detailed unstructured or structured model.
Induction of T4 DNA ligase in a recombinant strain of Escherichia coli
Authors: Whitney Gordon K. , Glick Bernard R. , Robinson Campbell W. 
Published: May 2005

AbstractThe kinetics of cell growth and foreign protein production, as well as factors affecting protein stability, were studied and optimized in batch and fed‐batch fermentations of a recombinant strain of Escherichia coli. The pL promoter from bacteriophage lambda under the control of a temperature‐sensitive cl represser, with the entire construct integrated into the E. coli chromosome through the use of a defective bacteriophage lambda lysogen, was used to direct the synthesis of T4 DNA ligase. The biphasic fermentations consisted of a primary growth phase at 30°C followed by an induction phase which was initiated by shifting the temperature to 42°C. In the fed‐batch fermentations, additional nutrients were added at the time of initiating induction. Maintenance of sufficiently high concentrations of the organic substrates (glucose and casamino acids) during the induction phase was required for continued cell growth at 42°C. Such growth was essential for T4 DNA ligase formation and in vivo stability. Hence, fed‐batch fermentations produced the highest yield of the foreign protein Commensurate with providing lower total amounts of substrates. In such cases, high cell densities (6 g dry wt/L) with substantial intracellular levels of T4 DNA ligase (4.6% total cellular protein, or 2.7% of the dry biomass) were achieved.
Adaptive on‐line optimizing control of bioreactor systems
Authors: Shi Zhongping , Shimizu Kazuyuki , Watanabe Norihiro , Kobayashi Takeshi 
Published: May 2005

AbstractSeveral on‐line optimizing control strategies were proposed and tested by computer simulation for the efficient operation of bioreactors. The control task was divided into two, one of which was to search for the optimal operating point and passed the set point to the lower layer of which task was to make the process output follow the set point as soon as possible. It was shown to be effective for the upper layer to express the objective function as a polynomial with respect to the measurement variable and to make use of it for finding the optimum point. Noting that the major dynamic characteristics of bioreactor system is the time‐varying and nonlinear nature, the adaptive type control system is in evitable. It was shown to be quite effective to use discrete type self‐tuning PID controller and the optimal controller compensated for the interaction between the control loops.Application was made to the cell recycle system for the production of lactic acid and baker's yeast cultivation. I was found from the former application that the control quality can be significantly improved by incorporating the decoupling strategy into the lower layer closed‐loop system. It was also found from the latter application that the initial startup period can be significantly reduced by making use of the rough mathematical model.
A mathematical model for the growth of a single cell of E. coli on a glucose/glutamine/ammonium medium
Authors: Shu J. , Shuler M. L. 
Published: May 2005

AbstractExtension of a single cell model of E. coli B/r to make predictions of culture response to variations in glutamine/glucose/ammonium ion concentrations is described. A biphasic glutamine transport system, a nitrogen metabolism scheme that includes glutamate dehydrogenase (GDH), glutamine synthetase/glutamate synthase (GS/GOGAT), the glutaminase routes, and a transaminase mechanism for glutamine carbon usage are added to the prototype model. The predictions of the extended model with regard to nutrient concentrations and cell size compare well with the experimental data and the prototype model predictions, demonstrating the capability of the integrated kinetic model to illustrate important enzymological interactions in a biological system. The discrepancies between the experimental data and the model predictions on growth yield suggest that a more detailed regulatory system of the TCA cycle is required for a more accurate energy budget.
Batch and continuous 2‐heptanone production by Ca‐alginate/Eudragit RL entrapped spores of Penicillium roquefortii
Authors: Larroche Christian , Gros Jean‐Bernard 
Published: May 2005

AbstractThe synthesis of 2‐heptanone from octanoic acid by Caalginate/Eudragit RL entrapped spores of Penicillium roquefortii is performed in batch and continuous reactions. The measurement of the HCI solution needed to overcome the pH increase during the course of a reaction allows continuous monitoring of the reaction progress of batch as well as continuous processes without any aliquot sampling. The hydration of the biocatalyst prior to a bioconversion performance is of major importance to achieve reproducible results. A continuous reaction carried out at pH 6.5 for one month demonstrates the feasibility of such a process and shows that the reaction occurs with a Michaelian behavior, with KM = 1.82 mmol/L and rsm = 0.82 mmol/L h, and no intraparticle diffusion limitation is found. The complex behavior of the spores during batch reactions makes this kind of operation unsuitable for kinetic studies.