bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental investigation of the external nitrification biological nutrient removal activated sludge (ENBNRAS) system
Authors: Hu Zhi‐rong , Sötemann S. , Moodley R. , Wentzel M. C. , Ekama G. A. 
Published: May 2003

AbstractA systematic lab‐scale experimental investigation is reported for the external nitrification (EN) biological nutrient removal (BNR) activated sludge (ENBNRAS) system, which is a combined fixed and suspended medium system. The ENBNRAS system was proposed to intensify the treatment capacity of BNR‐activated sludge (BNRAS) systems by addressing two difficulties often encountered in practice: (a) the long sludge age for nitrification requirement; and (b) sludge bulking. In the ENBNRAS system, nitrification is transferred from the aerobic reactor in the suspended medium activated sludge system to a fixed medium nitrification system. Thus, the sludge age of the suspended medium activated sludge system can be reduced from 20 to 25 days to 8 to 10 days, resulting in a decrease in reactor volume per ML wastewater treated of about 30%. Furthermore, the aerobic mass fraction can also be reduced from 50% to 60% to <30% and concommitantly the anoxic mass fraction can be increased from 25% to 35% to >55% (if the anaerobic mass fraction is 15%), and thus complete denitrification in the anoxic reactors becomes possible. Research indicates that both the short sludge age and complete denitrification could ameliorate anoxic aerobic (AA) or low food/microorganism (F/M) ratio filamentous bulking, and hence reduce the surface area of secondary settling tanks or increase the treatment capacity of existing systems. The lab‐scale experimental investigations indicate that the ENBNRAS system can obtain: (i) very good chemical oxygen demand (COD) removal, even with an aerobic mass fraction as low as 20%; (ii) high nitrogen removal, even for a wastewater with a high total kjeldahl nitrogen (TKN)/COD ratio, up to 0.14; (iii) adequate settling sludge (diluted sludge volume index [DSVI] <100 mL/g); and (iv) a significant reduction in oxygen demand. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 260–273, 2003.
Expression of a synthetic copy of the bovine chymosin gene in Aspergillus awamori from constitutive and pH‐regulated promoters and secretion using two different pre‐pro sequences
Authors: Cardoza R. E. , Gutiérrez S. , Ortega N. , Colina A. , Casqueiro J. , Martín J. F. 
Published: May 2003

AbstractA copy of the bovine chymosin gene (chy) with a codon usage optimized for its expression in Aspergillus awamori was constructed starting from synthetic oligonucleotides. To study the ability of this filamentous fungus to secrete bovine prochymosin, two plasmids were constructed in which the transcriptional, translational, and secretory control regions of the A. nidulans gpdA gene and pepB genes were coupled to either preprochymosin or prochymosin genes. Secretion of a protein enzymatically and immunologically indistinguishable from bovine chymosin was achieved in A. awamori transformants with each of these constructions. In all cases, the primary translation product (40.5 kDa) was self‐processed to a mature chymosin polypeptide having a molecular weight of 35.6 kDa. Immunological assays indicated that most of the chymosin was secreted to the extracellular medium. Hybridization analysis of genomic DNA from chymosin transformants showed chromosomal integration of prochymosin sequences and, in some transformants, multiple copies of the expression cassettes were observed. Expression from the gpdA promoter was constitutive, whereas expression from the pepB promoter was strongly influenced by pH. A very high expression from the pepB promoter was observed during the growth phase. The A. awamori pepB gene terminator was more favorable for chymosin production than the S. cerevisiae CYC1 terminator. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 249–259, 2003.
Lipase‐catalyzed ethanolysis of fish oils: Multi‐response kinetics
Authors: Torres Carlos F. , Moeljadi Marlina , Hill Charles G. 
Published: May 2003

AbstractThe kinetics of the lipase‐catalyzed (Pseudomonas cepacia) ethanolysis of fish oil has been studied in a batch reactor using menhaden oil, tuna oil, and acylglycerol mixtures derived from menhaden oil. Multi‐response models derived from a generalized Michaelis–Menten mechanism were developed to describe the rates of formation of ethyl esters of the primary fatty acids present in the precursor oil. A first‐order model for deactivation of the lipase was fit simultaneously to one of the data sets. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 274–281, 2003.
Kinetic modeling of the light‐dependent photosynthetic activity of the green microalga Chlorella vulgaris
Authors: Yun Yeoung‐Sang , Park Jong Moon 
Published: May 2003

AbstractLight‐dependent photosynthesis of Chlorella vulgaris was investigated by using a novel photosynthesis measurement system that could cover wide ranges of incident light and cell density and reproduce accurate readings. Various photosynthesis models, which have been reported elsewhere, were classified and/or reformulated based upon the underlying hypotheses of the light dependence of the algal photosynthesis. Four types of models were derived, which contained distinct light‐related variables such as the average or local photon flux density (APFD or LPFD) and the average or local photon absorption rate (APAR or LPAR). According to our experimental results, the LPFD and LPAR models could predict the experimental data more accurately although the APFD and APAR models have been widely used for the kinetic study of microalgal photosynthesis. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 303–311, 2003.
Inhibitory effect of carbon dioxide on the fed‐batch culture of Ralstonia eutropha: Evaluation by CO2 pulse injection and autogenous CO2 methods
Authors: Shang Longan , Jiang Min , Ryu Chul Hee , Chang Ho Nam , Cho Soon Haeng , Lee Jong Won 
Published: May 2003

AbstractIn order to see the effect of CO2 inhibition resulting from the use of pure oxygen, we carried out a comparative fed‐batch culture study of polyhydroxybutyric acid (PHB) production by Ralstonia eutropha using air and pure oxygen in 5‐L, 30‐L, and 300‐L fermentors. The final PHB concentrations obtained with pure O2 were 138.7 g/L in the 5‐L fermentor and 131.3 g/L in the 30‐L fermentor, which increased 2.9 and 6.2 times, respectively, as compared to those obtained with air. In the 300‐L fermentor, the fed‐batch culture with air yielded only 8.4 g/L PHB. However, the maximal CO2 concentrations in the 5‐L fermentor increased significantly from 4.1% (air) to 15.0% (pure O2), while it was only 1.6% in the 30‐L fermentor with air, but reached 14.2% in the case of pure O2. We used two different experimental methods for evaluating CO2 inhibition: CO2 pulse injection and autogenous CO2 methods. A 10 or 22% (v/v) CO2 pulse with a duration of 3 or 6 h was introduced in a pure‐oxygen culture of R. eutropha to investigate how CO2 affects the synthesis of biomass and PHB. CO2 inhibited the cell growth and PHB synthesis significantly. The inhibitory effect became stronger with the increase of the CO2 concentration and pulse duration. The new proposed autogenous CO2 method makes it possible to place microbial cells under different CO2 level environments by varying the gas flow rate. Introduction of O2 gas at a low flow rate of 0.42 vvm resulted in an increase of CO2 concentration to 30.2% in the exit gas. The final PHB of 97.2 g/L was obtained, which corresponded to 70% of the PHB production at 1.0 vvm O2 flow rate. This new method measures the inhibitory effect of CO2 produced autogenously by cells through the entire fermentation process and can avoid the overestimation of CO2 inhibition without introducing artificial CO2 into the fermentor. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 312–320, 2003.
Model‐based analysis of anaerobic acetate uptake by a mixed culture of polyphosphate‐accumulating and glycogen‐accumulating organisms
Authors: Zeng Raymond J. , Yuan Zhiguo , Keller Jürg 
Published: May 2003

AbstractAn increasing number of studies shows that the glycogen‐accumulating organisms (GAOs) can survive and may indeed proliferate under the alternating anaerobic/aerobic conditions found in EBPR systems, thus forming a strong competitor of the polyphosphate‐accumulating organisms (PAOs). Understanding their behaviors in a mixed PAO and GAO culture under various operational conditions is essential for developing operating strategies that disadvantage the growth of this group of unwanted organisms. A model‐based data analysis method is developed in this paper for the study of the anaerobic PAO and GAO activities in a mixed PAO and GAO culture. The method primarily makes use of the hydrogen ion production rate and the carbon dioxide transfer rate resulting from the acetate uptake processes by PAOs and GAOs, measured with a recently developed titration and off‐gas analysis (TOGA) sensor. The method is demonstrated using the data from a laboratory‐scale sequencing batch reactor (SBR) operated under alternating anaerobic and aerobic conditions. The data analysis using the proposed method strongly indicates a coexistence of PAOs and GAOs in the system, which was independently confirmed by fluorescent in situ hybridization (FISH) measurement. The model‐based analysis also allowed the identification of the respective acetate uptake rates by PAOs and GAOs, along with a number of kinetic and stoichiometric parameters involved in the PAO and GAO models. The excellent fit between the model predictions and the experimental data not involved in parameter identification shows that the parameter values found are reliable and accurate. It also demonstrates that the current anaerobic PAO and GAO models are able to accurately characterize the PAO/GAO mixed culture obtained in this study. This is of major importance as no pure culture of either PAOs or GAOs has been reported to date, and hence the current PAO and GAO models were developed for the interpretation of experimental results of mixed cultures. The proposed method is readily applicable for detailed investigations of the competition between PAOs and GAOs in enriched cultures. However, the fermentation of organic substrates carried out by ordinary heterotrophs needs to be accounted for when the method is applied to the study of PAO and GAO competition in full‐scale sludges. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 293–302, 2003.
Effects of buffering conditions and culture pH on production rates and glycosylation of clinical phase I anti‐melanoma mouse IgG3 monoclonal antibody R24
Authors: Müthing Johannes , Kemminer Sven E. , Conradt Harald S. , Šagi Dijana , Nimtz Manfred , Kärst Uwe , Peter‐Katalinić Jasna 
Published: May 2003

AbstractR24, a mouse IgG3 monoclonal antibody (MAb) against ganglioside GD3 (Neu5Acα8Neu5Acα3Gal β4Glcβ1Cer), can block tumor growth as reported in a series of clinical trials in patients with metastatic melanoma. The IgG molecule basically contains an asparagine‐linked biantennary complex type oligosaccharide on the CH2 domain of each heavy chain, which is necessary for its in vivo effector function. The purpose of this study was to investigate the biotechnological production and particularly the glycosylation of this clinically important MAb in CO2/HCO3− (pH 7.4, 7.2, and 6.9) and HEPES buffered serum‐free medium. Growth, metabolism, and IgG production of hybridoma cells (ATCC HB‐8445) were analyzed on a 2‐L bioreactor scale using fed‐batch mode. Specific growth rates (μ) and MAb production rates (qIgG) varied significantly with maximum product yields at pH 6.9 (qIgG = 42.9 μg 10−6 cells d−1, μ = 0.30 d−1) and lowest yields in pH 7.4 adjusted batches (qIgG = 10.8 μg 10−6 cells d−1, μ = 0.40 d−1). N‐glycans were structurally characterized by high pH anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD), matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF), and electrospray‐ionization quadrupole time‐of‐flight (ESI‐QTOF) mass spectrometry (MS). The highest relative amounts of agalacto and monogalacto biantennary complex type oligosaccharides were detected in the pH 7.2 (46% and 38%, respectively) and pH 6.9 (44% and 40%, respectively) cultivations and the uppermost quantities of digalacto (fully galactosylated) structures in the pH 7.4 (32%) and the HEPES (26%) buffered fermentation. In the experiments with HEPES buffering, antibodies with a molar Neu5Ac/Neu5Gc ratio of 3.067 were obtained. The fermentations at pH 7.2 and 6.9 resulted in almost equal molar Neu5Ac/Neu5Gc ratios of 1.008 and 0.985, respectively, while the alkaline shift caused a moderate overexpression of Neu5Ac deduced from the Neu5Ac/Neu5Gc quotient of 1.411. Different culture buffering gave rise to altered glycosylation pattern of the MAb R24. Consequently, a detailed molecular characterization of MAb glycosylation is generally recommended as a part of the development of MAbs for targeted in vivo immunotherapy to assure biochemical consistency of product lots and oligosaccharide‐dependent biological activity. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 321–334, 2003.
Properties of a novel magnetized alginate for magnetic resonance imaging
Authors: Shen Feng , Poncet‐Legrand Celine , Somers Sat , Slade Andrea , Yip Christopher , Duft Andy M. , Winnik Françoise M. , Chang Patricia L. 
Published: May 2003

AbstractImplanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once implanted, these microcapsules cannot be assessed without invasive surgery. We now report the preparation and characterization of a novel ferrofluid to render these microcapsules visible with magnetic resonance imaging (MRI). The ferrofluid was prepared as a colloidal iron oxide stabilized in water by alginate. The presence of iron particles in the ferrofluid was verified with chemical titration, dynamic light scattering, and magnetization measurement. The microcapsules fabricated with various concentrations of the ferrofluid in the core, or on the surface of alginate microcapsules, or both, all produced microcapsules with smooth surfaces as shown with light and scanning electron microscopy. However, at the nanoscale level, as revealed with atomic force microscopy, the ferrofluid‐fabricated microcapsules demonstrated increased granularity, particularly when the ferrofluid was used to laminate the surface. From the force spectroscopy measurements, these modified microcapsules showed increasing surface rigidity in the following order: traditional alginate < ferrofluid in the core < ferrofluid on the surface. Although the mechanical stability of low‐concentration ferrofluid (0.1%) microcapsules was reduced, increasing concentrations, up to 20%, were able to improve stability. When these ferrofluid microcapsules were examined with MRI, their T2 relaxation time was reduced, thereby producing increased contrast readily detectable with MRI, whereas the traditional alginate microcapsules showed no difference when compared with water. In conclusion, such ferrofluid‐enhanced alginate is suitable for fabricating microcapsules that offer the potential for in vivo tracking of implanted microcapsules without invasive surgery. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 282–292, 2003.
Production of savinase and population viability of Bacillus clausii during high‐cell‐density fed‐batch cultivations
Authors: Christiansen Torben , Michaelsen Søren , Wümpelmann Mogens , Nielsen Jens 
Published: May 2003

AbstractThe growth and product formation of a Savinase‐producing Bacillus clausii were investigated in high‐cell‐density fed‐batch cultivations with both linear and exponential feed profiles. The highest specific productivity of Savinase was observed shortly after the end of the initial batch phase for all feed profiles applied and, in addition, there was a time‐dependent decrease in specific productivity. The specific glucose uptake rate increased with time for constant specific growth rate indicating that the maintenance requirements increased with time, possibly due to a decreasing K+ concentration. The physiological state of the cells was monitored during the cultivations using a flow cytometry assay based on the permeability of the cell membrane to propidium iodide. In the latter parts of the fed‐batch cultures with a linear feed profile, a large portion of the cell population was found to have a permeable membrane, indicating a large percentage of dead cells. By assuming that only cells with a nonpermeable membrane contributed to growth and product formation, the physiological properties of this subpopulation were calculated. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 344–352, 2003.
Multicriteria optimization of biochemical systems by linear programming: Application to production of ethanol by Saccharomyces cerevisiae
Authors: Vera Julio , De Atauri Pedro , Cascante Marta , Torres Néstor V. 
Published: May 2003

AbstractIn this study we present a method for simultaneous optimization of several metabolic responses of biochemical pathways. The method, based on the use of the power law formalism to obtain a linear system in logarithmic coordinates, is applied to ethanol production by Saccharomyces cerevisiae. Starting from an experimentally based kinetic model, we translated it to its power law equivalent. With this new model representation, we then applied the multiobjective optimization method. Our intent was to maximize ethanol production and minimize each of the internal metabolite concentrations. To ensure cell viability, all optimizations were carried out under imposed constraints. The different solutions obtained, which correspond to alternative patterns of enzyme overexpression, were implemented in the original model. We discovered few discrepancies between the S‐system‐optimized steady state and the corresponding optimized state in the original kinetic model, thus demonstrating the suitability of the S‐system representation as the basis for the optimization procedure. In all optimized solutions, the ATP level reached its maximum and any increase in its activity positively affected the optimization process. This work illustrates that in any optimization study no single criteria is of general application being the multiobjective and constrained task the proper way to address it. It is concluded that the proposed multiobjective method can serve to carry out, in a single study, the general pattern of behavior of a given metabolic system with regard to its control and optimization. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 335–343, 2003.
Continuous cultivations of a Penicillium chrysogenum strain expressing the expandase gene from Streptomyces clavuligerus: Growth yields and morphological characterization
Authors: Robin J. , Lettier G. , McIntyre M. , Noorman H. , Nielsen J. 
Published: May 2003

AbstractThe growth stoichiometry of a Penicillium chrysogenum strain expressing the expandase gene from Streptomyces clavuligerus was determined in glucose‐limited chemostat cultivations using a chemically defined medium. This strain produces adipoyl‐7‐aminodeacetoxycephalosporanic acid (ad‐7‐ADCA) when it is fed with adipic acid. The biomass yield and maintenance coefficients for the strain were similar to those found for penicillin‐producing strains of Penicillium chrysogenum. The maximum specific growth rate in the chemostat was found to be 0.11 h−1. Metabolic degradation of adipate was found to take place in significant amounts only at dilution rates below 0.03 h−1. After three to five residence times, adipate degradation and ad‐7‐ADCA production disappeared, and this allowed determination of the biomass yield coefficient on adipate. The morphology was measured at different dilution rates and the mean total hyphal length and mean number of tips both increased with an increase in dilution rate from 0.015 to 0.065 h−1. Both variables decreased when the dilution rate was increased above 0.065 h−1. A correlation between mean total hyphal length and productivity of ad‐7‐ADCA was found. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 361–368, 2003.
Continuous cultivations of a Penicillium chrysogenum strain expressing the expandase gene from Streptomyces clavuligerus: Kinetics of adipoyl‐7‐aminodeacetoxycephalosporanic acid and byproduct formations
Authors: Robin J. , Bruheim P. , Nielsen M. L. , Noorman H. , Nielsen J. 
Published: May 2003

AbstractThe production kinetics of a transformed strain of Penicillium chrysogenum expressing the expandase gene from Streptomyces clavuligerus was investigated in chemostat cultivations. The recombinant strain produces adipoyl‐7‐aminodeacetoxycephalosporanic acid (ad‐7‐ADCA) as the major product; however, during the cultivations, the appearance of a major unknown and poorly secreted product was observed. Investigations using high‐performance liquid chromatography (HPLC) and liquid chromatography–mass spectroscopy (LC‐MS) showed that this byproduct has a six‐membered dihydrothiazine ring, which is characteristic for cephalosporins. The byproduct may be formed via isopenicillin N by as‐yet unknown mechanisms, but involving expandase. It is likely that the unknown compound (UC) is deacetoxycephalosporin C (DAOC). Investigation of the instability of the various β‐lactams produced showed higher instability for compounds with a five‐membered thiazolidine ring than those with a six‐membered dihydrothiazine ring. Furthermore, secretion of products and byproducts was shown to be quite different. The productivity was studied as a function of the dilution rate in the range 0.015 to 0.090 h−1. The specific productivity of total β‐lactams was compared with that of the penicillin‐G‐producing host strain, and it was found to be lower at dilution rates of <0.06 h−1. Quantification of the fluxes through the pathway leading to ad‐7‐ADCA showed a decrease in flux toward ad‐7‐ADCA, and an increase in flux toward UC as the dilution rate increased. Northern analysis of the biosynthetic genes showed that expression of the enzymes involved in the ad‐7‐ADCA pathway decreased as the dilution rate increased. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 353–360, 2003.
Synthesis, Receptor Binding, Molecular Modeling, and Proliferative Assays of a Series of 17α‐Arylestradiols
Authors: Foy Nicolas , Stéphan Elie , Vessières Anne , Salomon Emmanuel , Heldt Jan‐Martin , Huché Michel , Jaouen Gérard 
Published: June 2003

AbstractA series of new derivatives of estradiol substituted at position 17α by various aryls has been synthesized. This was made possible by efficient activation methods for the addition of aryllithiums to the carbonyl group at position 17 of estrone by using tetramethylethylenediamine (TMEDA) or BF3⋅OEt2. Their relative binding affinity (RBA) for the α and the β forms of the estrogen receptor (ER) have been measured. All except one of the compounds synthesized had an RBA value of around 10 % which indicates a level of tolerance towards the bulky substituent at position 17. The lipophilicity values measured for these compounds are higher than that found for estradiol (E2). A study of their proliferative/antiproliferative effects was carried out on hormone‐dependent (MCF7) and hormone‐independent (MDA‐MB231) breast cancer cell lines. It is interesting to note that all the compounds are estrogenic. The possibility of easily attaching an iodine at the end of a phenyl spacer opens up a route to new radiopharmaceuticals for use in radioimaging.