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  • 1
    Electronic Resource
    Electronic Resource
    Oxygen transfer in a multiple air-lift loop reactor (1995)
    Springer
    Bioprocess and biosystems engineering 12 (1995), S. 167-172 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Multiple Air-lift Loop reactor (MAL) is a new type of bioreactor, in which a series of airlifts with internal loops is incorporated into one vessel. As such, the MAL is an approximation of an aerated plug-flow fermenter. Gas/liquid oxygen transfer was studied as a function of the gas flow rate in a MAL. The second MAL-compartment in the series was investigated in particular, and a Rectangular Air-lift Loop reactor (RAL) was used as a reference. Both a dynamic and a steady-state method were used for the determination of the overall volumetric oxygen-transfer coefficient. Both methods gave the same results. The oxygen transfer coefficient in the second MAL-compartment was low compared to that of conventional internal-loop reactors. Wall effects probably caused bubble coalescence and a reduction in the oxygen transfer. For the RAL it was found that oxygen transfer was comparable to that in a bubble column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01767462
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen transfer in a multiple air-lift loop reactor (1995)
    Springer
    Bioprocess engineering 12 (1995), S. 167-172 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The Multiple Air-lift Loop reactor (MAL) is a new type of bioreactor, in which a series of airlifts with internal loops is incorporated into one vessel. As such, the MAL is an approximation of an aerated plug-flow fermentor. Gas/liquid oxygen transfer was studied as a function of the gas flow rate in a MAL. The second MAL-compartment in the series was investigated in particular, and a Rectangular Air-lift Loop reactor (RAL) was used as a reference. Both a dynamic and a steady-state method were used for the determination of the overall volumetric oxygen-transfer coefficient. Both methods gave the same results. The oxygen transfer coefficient in the second MAL-compartment was low compared to that of conventional internal-loop reactors. Wall effects probably caused bubble coalescence and a reduction in the oxygen transfer. For the RAL it was found that oxygen transfer was comparable to that in a bubble column. List of symbols A d [m2] cross-sectional downcomer area A r [m2] cross-sectional riser area a [m2 ⋅ m-3] specific gas/liquid interfacial surface area c l [mol ⋅ m-3] actual oxygen concentration in the liquid c s [mol ⋅ m-3] saturation oxygen concentration d b [m] mean bubble diameter H w [m] separator-wall height H l [m] liquid height above reactor base k ol [m ⋅ s-1] overall oxygen transfer coefficient R 2 [m] inner radius for the separator wall in the second MAL compartment T [°C] temperature t [s] time ν gs [m ⋅ s-1] superficial gas velocity w [m] separator-wall thickness α [–] overall gas holdup ρ [kg ⋅ m-3] density τ m [s] mixing time Φ l [m3 ⋅ s-1] liquid flow rate Subscripts d de-oxygenation vessel in incoming out outcoming r reactor
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01767462
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of low serum concentrations (0%-2.5%) on growth, production, and shear sensitivity of hybridoma cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 179-182 
    Details
    ISSN: 0006-3592
    Keywords: animal-cell culture ; hybridoma ; reduced serum content ; shear sensistivity ; bubble-column design ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a stirred culture of hybridoma cells, the effects of serum reduction from 2.5% to 0% on growth and monoclonal antibody porduction have been investigated. The shear sensitivity of cells from the same culture has been tested in a bubble column. Serum reduction does not greatly affect viable-cell concentrations, but cell specific monoclonal-antibody production rate shows a decreasing trend. A gradual increase in sensitivity for sparging, which is nor the result of a long-term biological effect, has beeen measured in a bubble column at decreasing fetal calf serum concentrations. Finally, the hypothetical killing-volume model describing the death rate of insect cells in bubble columns has now been completely validated for the pertinent hybridoma-cell line.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400125
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrodynamics and mixing in a multiple air-lift loop reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 994-1001 
    Details
    ISSN: 0006-3592
    Keywords: multiple air-lift loop reactor ; reactor series ; plug flow ; hydrodynamics ; modeling ; mixing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new bioreactor, in which a series of air-lift reactors with an internal loop is incorporated into one vessel, is introduced. With this multiple air-lift loop reactor (MAL) and approximation of an aerated plug-flow fermentor is strived for. Mixing, liquid velocity, and gas holdup were measured as a function of the gas flow rate in this new internal-loop reactor geometry. As a reference, hydrodynamics were also investigated in a conventional internal-loop reactor. A model description of the hydrodynamics in the second compartment of the MAL is given. This model is based on a two-phase, drift-flux model and a friction coefficient. Frictional losses were independent of the reactor bottom geometry, and were observed to increase with the gas flow rate as a result of the presence of stationary gas bubbles in the downcomer. The hydrodynamics and mixing of the second MAL compartment were comparable with those of conventional internal-loop reactors. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420810
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Hybridomas in a bioreactor cascade: modeling and determination of growth and death kinetics (1996)
    Springer
    Cytotechnology 21 (1996), S. 263-277 
    Details
    ISSN: 1573-0778
    Keywords: hybridomas ; serum-free medium ; monoclonal antibodies ; reactor series ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridomas were cultured under steady-state conditions in a series of two continuous stirred-tank reactors (CSTRs), using a serum-free medium. The substrate not completely converted in the first CSTR, was transported with the cells to the second one and very low growth rates, high death rates, and lysis of viable cells were observed in this second CSTR. These conditions are hardly accessible in a single vessel, because such experiments would be extremely time-consuming and unstable due to a low viability. In contrast to what is often observed in literature, kinetic parameters could thus be derived without the neccessity for extrapolation to lower growth rates. Good agreement with literature averages for other hybridomas was found. Furthermore, showing that the reactor series is a valuable research tool for kinetic studies under extreme conditions, the possibility to observe cell death under stable and defined steady-state conditions offers interesting opportunities to investigate apoptosis and necrosis. Additionally, a model was developed that describes hybridoma growth and monoclonal antibody production in the bioreactor cascade on the basis of glutamine metabolism. Good agreement between the model and the experiments was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365349
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    Paper (German National Licenses)
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