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  • 1
    ISSN: 0006-3592
    Keywords: bioreactor ; tower loop bioreactor ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 437-450 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the cultivation of E. coli in an airlift tower-loop bioreactor, the following properties were measured: transverse profiles of Sauter bubble diameter, dS; local relative gas holdup, EG; bubble rise velocity, uBS; local mean velocity, ū turbulence intensity, u′; macrotime scale, TEL; dissipation time scale, τE; power spectrum, E(n); and energy dissipation spectrum D(n) at different distances from the aerator. The influence, distance from the aerator, absence and/or presnece of cells, and batch and/or continuous-culture operation on the behavior of the two-phase system are discussed on the basis of these properties.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0006-3592
    Keywords: bioreactor ; tower loop bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Investigations were carried out in a 9 m high, 4 m3 volume, pilot plant airlift tower loop bioreactor with a draft tube. The reactor was characterized by measuring residence time distributions of the gas phase using pseudostochastic tracer signals and a mass spectrometer and by evaluating the mixing in the liquid phase with single-pulse tracer inputs. The local gas holdup and the bubble size (piercing length) were measured with two-channel electrical conductivity probes. The mean residence times and the intensities of the axial mixing in the riser and downcomer and the circulation times of the phases as well as the fraction of the recirculated gas phase were evaluated. The gas holdup in the riser is nearly uniform along the reactor. In the downcomer, it diminishes from top to bottom. The liquid phase dispersion coefficients, DL, are smaller than those measured in the corresponding bubble columns. In the pilot plant with tap water the following relationship was found: DLr = cwSGn; with c = 203.4; n = 0.5;DLr(cm2 s-1;) and WSG(cm s-1) where DLr is the longitudinal dispersion coefficient in the riser and WSG is the superficial gas velocity. The gas phase dispersion coefficients in the riser of the pilot plant, DGr, are also enlarged with increasing superficial gas velocity, WSG, however, no simple relationship exists. Parameter DGr is the highest in the presence of antifoam agents, intermediate in tap water, and the smallest in ethanol solution.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3592
    Keywords: yeast cultivation ; airlift tower loop reactor ; pseudostochastic tracer signals ; axial mixing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Saccharomyces cerevisiae was cultivated in a 4-m3 pilot plant airlift tower loop reactor with a draft tube in batch and continuous operations and for comparison in a laboratory airlift tower loop reactor of 0.08 m3 volume. The reactors were characterized during and after the cultivation by measuring the distributions of the residence times of the gas phase with pseudostochastic tracer signals and mass spectrometer and by evaluating the mixing in the liquid phase with a pulse-shaped volatile tracer signal and mass spectrometer as a detector. The mean residence times and the intensities of the axial mixing in the riser and downcomer, the circulation times of the gas phase, and the fraction of the recirculated gas phase were evaluated and compared.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 52 (1996), S. 248-258 
    ISSN: 0006-3592
    Keywords: two-phase gas-liquid flow ; bubble columns ; dynamic three-dimensional numerical simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Detailed measurements of multiphase flows that prevail in bioreactors tell us that different transport mechanisms are dominating on different observation scales. The consequence in terms of reactor modeling is that the processes on different scales can be treated independently. A three-dimensional, dynamical model is presented that can be used to describe bubble column bioreactors on the reactor scale. It is based on the Navier-Stokes equation system. On the next smaller scale, the dynamics of the gas phase is described in a Lagrangian way, by tracking many bubble clusters or bubbles simultaneously on their way through the reactor. The model is capable of describing bubble columns of different size and can thus be used for scale-up. Its performance is demonstrated with a production-scale beer fermentor. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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