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  • 1
    Electronic Resource
    Electronic Resource
    Flux Adaptations of Citrate Synthase—deficient Escherichia coli (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 745 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb44362.x
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  • 2
    Electronic Resource
    Electronic Resource
    Observing protein synthesis, export, and tryptophan incorporation by front-surface fluorescence (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 13-19 
    Details
    ISSN: 0006-3592
    Keywords: front-surface detection ; bacterial fermentations ; protein fluorescence ; diauxic growth ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Front-surface detection of emission from fluorophores in the presence and absence of light-scattering particles was contrasted to right-angle and wave-guide detection. We found that front-surface detection was the least prone to the reabsorption, inner-filtering, and scattering effects that can plague fluorescent measurements. Front-surface detection was thus used to assess the use of protein and ANS fluorescence as a means of monitoring events in bacterial fermentations. Protein fluorescence appeared to track well changes in optical density during balanced growth. However, during the lag associated with diauxic growth and after exposure to ampicillin, protein fluorescence became decoupled from cellular growth in a manner consistent with prior observations and the known effect of ampicillin on cells. ANS proved to be nontoxic and capable of reporting the occurrence of protein release from cells. The spectral shifts of tryptophan indicated that the incorporation of tryptophan into cellular protein can be monitored.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390104
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  • 3
    Electronic Resource
    Electronic Resource
    Cultivator for NMR studies of suspended cell cultures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1359-1366 
    Details
    ISSN: 0006-3592
    Keywords: NMR studies ; cell cultures ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When nuclear magnetic resonance (NMR) spectroscopy is employed for physiological experiments with suspended cells, providing for adequate nutrient and oxygen delivery is particularly important, because the inherent insensitivity of NMR requires that concentrated cell suspensions be used. In addition, it is desirable to be able to manipulate the growth rate of cells during a NMR experiment. To address these concerns, a continuous cell cultivator that provides convective oxygen and nutrient transport has been constructed for NMR experiments. The NMR detector coil is located within the cultivator volume. The location is advantageous because the rapid exchange of cells in and out of the coil leads to a small apparent spin lattice relaxation time, thus allowing for rapid pulsing and fast signal averaging. In this article we present the physical principles on which the cultivator's design is based. 31P spectra showing the response of continuously cultivated Saccharomyces cerevisiae cultures to a phosphate bolus and growth rate shift are then given. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260401110
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation and utilization of microsin promoter turn on in a chromosomal fusion (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 719-726 
    Details
    ISSN: 0006-3592
    Keywords: microsin B17 promoter ; fusion strain ; gene expression ; growth rate dependence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Prior work has demonstrated that the microsin antibiotics are produced by enteric bacteria when the growth medium is depleted of nutrients. Because the control loci could have biotechnical potential, and general stress-response phenomena are of importance to understanding how bacteria survive in natural and bioreactor environments, we examined further the growth rate dependence of gene expression under the control of the microsin B17 promoter. This work entailed performing batch and chemostat growth experiments with a strain of E. coli K-12 containing a mcbA-lacZ gene fusion in the chromosome. Our results indicate that when a culture is presented with excess respiratory substrate, a well defined growth rate exists, below which a significant induction event occurs. However, cultures that are fermenting or highly glycolytic tend to express poorly. Additionally, the utility of the fusion strain was examined by performing fed-batch cultivation experiments. We found that sustained production in a fed-batch reactor can be accomplished by using a straightforward, exponential nutrient feeding profile.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380705
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of regulatory mechanism on hyperbolic reaction network properties (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 166-178 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The notion that the regulated and flux-controlling enzyme in a metabolic network need not correspond suggests that the purpose of regulation may not be flux homeostasis under all physiological circumstances. Additionally, the fact that diversity in the function of intact metabolic networks exists suggests that in addition to time constant separation, other kinetic structure/regulatory mechanism patterns exist. In order to compliment and expand prior work on identifying kinetic structure-property relationships in networks, the present work explores in a general way how the control, dynamic, and energetic properties of metabolic networks depend on operating point, kinetic structure, and regulatory mechanism. The basic feature of trade-offs between properties is illustrated and used as a basis for indicating how particular subsets of structure, regulatory mechanism, and operating point emphasize certain properties that can be associated with a physiological function. Examples of scavenging trace metabolites and amphibolite coordination are proposed. Microstructure logic in terms of turnover number distributions as well as a potential mixed polynomial network analysis approach are also discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260360209
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  • 6
    Electronic Resource
    Electronic Resource
    Chemostat-cultivated Escherichia coli at high dilution rate: Multiple steady states and drift (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 179-190 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The representation of metabolic network reaction kinetics in a scaled, polynomial form can allow for the prediction of multiple steady states. The polynomial formalism is used to study chemostat-cultured Escherichia coli which has been observed to exhibit two multiple steady states under ammonium ion-limited growth conditions: a high cell density-low ammonium ion concentration steady state and a low cell density-high ammonium ion concentration steady state. Additionally, the low-cell-density steady state has been observed to drift to the high-cell-density steady state. Inspection of the steady-state rate expressions for the ammonium ion transport/assimilation network (in polynomial form) suggests that at low ammonium ion concentrations, two steady states are possible. One corresponds to heavy use of the glutamine synthetase-glutamate synthase (GLNS-GS) branch and the second to heavy use of the glutamate dehydrogenase (GDH) branch. Realization of the predicted intracellular steady states is also found to be dependent on the parameters of the transport process. Moreover, the two steady states differ in where their energy intensity lies. To explain the drift, GLNS, which is inducible under low ammonium ion concentrations, is suggested to be a “memory element.” A chemostat-based model is developed to illustrate that perturbations in dilution rate can lead to drift between the two steady states provided that the disturbance in dilution rate is sufficiently large and/or long in duration.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260360210
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  • 7
    Electronic Resource
    Electronic Resource
    Simple constrained-optimization view of acetate overflow in E. coli (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 732-738 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of acetate by aerobically growing E. coli is examined. The problem is formulated in terms of a flow network that has as its objective maximal ATP synthesis. It is found that when loads are imposed and flux constraints exist either at the level of NADH turnover rate or the activity of a key Krebs cycle enzyme, switching to acetate overflow is predicted. Moreover, the result found for the latter constraint can be shown to be formally equivalent to a correlation experimentally determined for the specific rate of acetate production by E. coli K-12.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350711
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