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Digitale Medien

Copolymerization kinetics of a model siloxane system (1997)

Rankin, Stephen E. ; Macosko, Christopher W. ; McCormick, Alon V.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1293-1302

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ISSN: 0887-624X

Schlagwort(e): methylethoxysilanes ; hydrolysis ; polycondensation ; sol-gel ; modeling ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Using 29Si NMR, we monitor the copolymerization of trimethylethoxysilane and dimethyldiethoxysilane (model compounds for more complex sol-gel copolymer systems) in a batch reactor. Under the chosen conditions, the extents of self- and cross-condensation reactions are readily determined. Using a nonideal polycondensation kinetic model, we show that the copolymerization rate coefficient for a pair of sites of differing functionality is bounded by their homopolymerization rate coefficients, lying closer to the larger one. This reactivity pattern generates a heterogeneous monomer distribution in the copolymerization products. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1293-1302, 1997

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

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2

Digitale Medien

Measurement and simulation of the morphological development of filamentous microorganisms (1992)

Yang, H. ; Reichl, U. ; King, R. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 39 (1992), S. 44-48

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ISSN: 0006-3592

Schlagwort(e): directional growth ; modeling ; morphology ; pellet formation ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Growth of Streptomyces tendae was investigated in submerged culture. Images of several mycelia were analyzed by means of an image-processing system. The studies revealed that tip growth angles and branching outgrowth angles could be regarded as normally distributed. Based on these results, a random model for directional growth of hyphal tips as well as directional growth of branches is proposed. This model shows curved elongation of hyphal tips, so that the morphological development of a mycelium up to the formation of a pellet is predicted, similar to that observed in nature.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260390108

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3

Digitale Medien

Xanthan production in bubble column and air-lift reactors (1992)

Suh, Ii-Soon ; Schumpe, Adrian ; Deckwer, Wolf-Dieter

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 39 (1992), S. 85-94

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ISSN: 0006-3592

Schlagwort(e): xanthan ; bubble column ; air life ; mixing ; oxygen transfer limitation ; modeling ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: A bubble column (0.05 m3) and an air-lift fermentor (1.2 m3) were used for the production of the exocellular microbial polysaccharide xanthan with Xanthomonas campestris in a synthetic medium. Upon oxygen depletion in the liquid, the xanthan production rate dropped sharply and then became a linear function of the oxygen transfer rate. The volumetric mass transfer coefficients for oxygen conformed to the correlation of Suh et al. Using this correlation in combination with the model for xanthan batch fermentation suggested by Peters et al., the xanthan fermentations in the bubble column were well described. The model also correctly predicted the time course of the molecular weight of the polysaccharide even when a complex medium was used. In the air-lift fermentor, however, the xanthan production rate and the xanthan yields with respect to oxygen and glucose were lower than expected at the overall oxygen transfer rate. The poor performance of the air lift was traced back to the lack of any oxygen supply in the downcomer.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260390113

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4

Digitale Medien

Solute exclusion from cellulose in packed columns: Process modeling and analysis (1992)

Neuman, R. P. ; Walker, L. P.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 40 (1992), S. 226-234

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ISSN: 0006-3592

Schlagwort(e): cellulose ; solute exclusion ; modeling ; surface area ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: In this investigation, process modeling and analysis were used to explore the behavior of solute exclusion from cellulose in packed columns. The study focused on modeling the effects of dispersion, mass transport, and pore diffusion. Three mathematical models were used to predict the behavior of the columns: an equilibrium model, a mass transfer model, and a combined mass transfer and pore diffusion model. Computer implementations of these models were tested against experimental conditions where cellulose particle size and solution velocity were used to either amplify or minimize dispersion or skewness in the elution curves. For small cellulose particles (200-300 mesh), all three models accurately predicted the shape of the elution curve and the particle porosity. For larger particles (45-60 mesh), the mass transfer model and the combined mass and pore diffusion model best represented the behavior of the column. At high solution velocities (0.63 cm3 min-1) and large particles, only the combined mass transfer and pore diffusion model accurately represent the column behavior. Sensitivity analysis revealed that the mass transfer coefficient had little effect on the elution curves for the range of values (10-6-10-3 cm s-1) calculated from the experimental data. The combined mass transfer and pore diffusion model presented in this article can be used to design solute exclusion measurement experiments for the larger cellulose particles found in a commercial cellulose-to-ethanol plant.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260400206

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5

Digitale Medien

Mechanism of insulin aggregation and stabilization in agitated aqueous solutions (1992)

Sluzky, Victoria ; Klibanov, Alexander M. ; Langer, Robert

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 40 (1992), S. 895-903

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ISSN: 0006-3592

Schlagwort(e): insulin aggregation kinetics ; protein stability ; stabilization strategies ; aggregation ; denaturation ; modeling ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Undesirable aggregation of aqueous insulin solutions remains a serious obstacle in the development of alternative methods of diabetes therapy. We investigated the fundamental nature of the aggregation mechanism and proposed stabilization strategies based on a mathematical model for the reaction scheme. Insulin aggregation kinetics in the presence of solid-liquid and air-liquid interfaces were monitored using UV spectroscopy and quasielastic light scattering (QELS). Experimental observations were consistent with our model of monomer denaturation at hydrophobic surfaces followed by the formation of stable intermediate species which facilitated subsequent macroaggregation. The model was used to predict qualitative trends in insulin aggregation behavior, to propose stabilization strategies, and to elucidate mechanisms of stabilization. In the absence of additives, insulin solutions aggregated completely (more than 95% of the soluble protein lost) within 24 h; with sugarbased nonionic detergents, no detectable loss occurred for more than 6 weeks. © 1992 John Wiley & Sons, Inc.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260400805

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6

Digitale Medien

Morphology of Trichoderma reesei QM 9414 in submerged cultures (1995)

Lejeune, R. ; Nielsen, J. ; Baron, G. V.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 47 (1995), S. 609-615

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ISSN: 0006-3592

Schlagwort(e): Trichoderma reesei ; image analysis ; morphology ; modeling ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The microscopic morphology of Trichoderma reesei QM 9414, growing in submerged culture, was studied by image analysis. The morphology was characterized by the total hyphal length, the total number of tips, the number of actively growing tips, and the length of the main hypha. To describe the growth of a single mycelium a simple model is set-up. The main features of the model are: (1) saturation type kinetics for the tip extension of the individual branches within the mycelium; and (2) random branching with a frequency function, which is proportional to the total hyphal length. The model is used to simulate a population of mycelia, where spore germination is described with a log-normal distribution. From the simulation of the population, the average properties of the mycelia, e.g., the average total hyphal length, are calculated, and by fitting the model to experimental data the model parameters are estimated. Finally, the distribution function with respect to the mycelia properties, that is, number of tips and total hyphal length, is calculated, and it corresponds well with the experimental determination of the distribution function. © 1995 John Wiley & Sons Inc.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260470513

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7

Digitale Medien

Modeling of an industrial alcohol fermentation and simuiation of the plant by a process simulator (1995)

Pascal, F. ; Dagot, C. ; Pingaud, H. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 46 (1995), S. 202-217

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ISSN: 0006-3592

Schlagwort(e): batch process ; steady-stage process ; fermentation ; modeling ; simulation ; ethanol ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The aim of the present study was the development of a general simulation module for fermentation within the framework of existing chemical process simulators. This module has been applied to an industrial plant which produces ethanol from beet molasses and fresh beet juice by Saccharomyces cerevisiae. An unstructured mechanistic model has been developed with kinetic laws that are based on a chemically defined reaction scheme which satisfies stoichiometric constraints. This model can be applied to different culture conditions and takes into account secondary byproducts such as higher alcohols. These byproducts are of prime importance and need to be correctly estimated because a sequence of distillation columns follow the fermentor in the plant. Important measurement campaigns have been performed on the plant to validate the model. Plant operation has been successfully simulated using the same kinetic model for both continuous and fed-batch modes of production. © 1995 John Wiley & Sons, Inc.

Zusätzliches Material: 12 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260460304

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8

Digitale Medien

A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: I. Coupling between light transfer and growth kinetics (1992)

Cornet, J. F. ; Dussap, C. G. ; Dubertret, G.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 40 (1992), S. 817-825

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ISSN: 0006-3592

Schlagwort(e): modeling ; kinetics ; cyanobacteria ; photobioreactors ; radiative transfer ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The study of the interactions between physical limitation by light and biological limitations in photobioreactors leads to very complex partial differential equations. Modeling of light transfer and kinetics and the assessment of radiant energy absorded in photoreactors require an equation including two parameters for light absorption and scattering in the culture medium. In this article, a simple model based on the simplified, monodimensional equation of Schuster for radiative transfer is discussed. This approach provides a simple way to determine a working illuminated volume in which growth occurs, therefore allowing indentification of kinetic parameters. These parameters might then be extended to the analysis of more complex geometries such as cylindrical reactors. Moreover, this model allows the behavior of batch or continuous cultures of cyanobacteria under light and mineral limitations to be predicted. © 1992 John Wiley & Sons, Inc.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260400709

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9

Digitale Medien

A unified stoichiometric model for oxidative and oxidoreductive growth of yeasts (1992)

Auberson, Lillian C. M. ; von Stockar, U.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 40 (1992), S. 1243-1255

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ISSN: 0006-3592

Schlagwort(e): calorimetry, Saccharomyces cerevisiae ; Kluyveromyces fragilis ; yeast metabolism ; modeling ; continuous culture ; respiratory capacity ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Yeasts degrade glucose through different metabolic pathways, where the choice of the pathway is dependent on the nature of the limitation in the various substrates. When oxygen is limiting in addition to glucose, yeasts often grow according to a mixture of oxidative and reductive metabolism. Oxygen may be limiting either by supply or by inherent biological restrictions such as the respiratory bottleneck in Saccharomyces cerevisiae or by both. A unified model incorporating both supply and biological limitations is proposed for the quantitative prediction of growth rates, consumption and production rates, as well as key metabolite concentrations during mixed oxidoreductive metabolism occuring as a result of such oxygen limitations. This simple unstructured model can be applied to different yeast strains while at the same time requiring a minimum number of measured parameters. “Estimators” are utilized in order to predict the presence of supply-side or biological limitations. The values of these estimators also characterize the relative importance of oxidative to total metabolism. Results from the aerobic and oxygen-limited chemostat cultures were used to corroborate the model predictions. During these experiments, the heat released by the yeast cultures was also monitored on-line. The model correctly predicted the overall stoichiometry, steady-state concentrations, and rates including heat dissipation rates measured in the various situations of oxygen limitations. Direct continuous measurements such as heat can be used in conjunction with the unified model for on-line proces control. © 1992 John Wiley & Sons, Inc.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260401014

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10

Digitale Medien

Development and experimental evaluation of a steady-state, multispecies biofilm model (1992)

Rittmann, Bruce E. ; Manem, Jacques A.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 39 (1992), S. 914-922

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ISSN: 0006-3592

Schlagwort(e): biofilm ; competition ; modeling ; multispecies ; nitrification ; species distribution ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: A steady-state model for quantifying the space competition in multispecies biofilms is developed. The model includes multiple active species, inert biomass, substrate utilization and diffusion within the biofilm, external mass transport, and detachment phenomena. It predicts the steady-state values of biofilm thickness, species distribution, and substrate fluxes. An experimental evaluation is carried out in completely mixed biofilm reactors in which slow-growing nitrifying bacteria compete with acetate-utilizing heterotrophs. The experimental results show that the model successfully describes the space competition. In particular, increasing acetate concentrations causes NH4+-N fluxes to decrease, because nitrifiers are forced deeper into the biofilm, where they experience greater mass-transport resistance.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260390906

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