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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 34 (1995), S. 928-935 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 782 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-0778
    Keywords: batch culture ; conditioned medium ; growth ; hybridoma ; inoculum ; protein productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Apart from gas concentrations, temperature, and pH, generally only the initial conditions can be manipulated in batch culture. Inoculum size and initial conditioned medium concentration represent two important considerations for optimal batch production. Two hybridoma cell lines were used to assess the impact of these initial conditions on population growth and monoclonal antibody productivity in suspension batch culture. Varying initial cell concentration over the range of 1.0 × 105 cells mL-1 to 3.0 × 105 cells mL-1 did not affect maximum product titre or maximum volumetric cell-hours attained. Initial percent of conditioned medium up to 40 percent strongly impacted on population growth and productivity, with initial levels of 30 to 40% conditioned medium reducing or eliminating lag phase and increasing average viable cell density. However, specific productivity and product titre declined with increasing initial percent conditioned medium, even on a per volume of fresh medium basis. Glutamine and glucose depletion or ammonia toxicity could cause depressed product titres when conditioned medium is used. Glutamine and glucose levels can easily be replenished in conditioned medium at minimal cost, and ammonia can be removed. Specific productivity was higher during cyclic batch operating mode than during batch operating mode. This may be because cyclic batch operating mode results in an incidental volume of conditioned medium at the beginning of each cycle. A two stage, cyclic-batch/batch operating mode can be employed to fully utilize medium and maximize product titre.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cytotechnology 26 (1998), S. 139-152 
    ISSN: 1573-0778
    Keywords: batch kinetics ; cell cycle ; cell-hours ; hybridoma ; population parameters ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Several methods exist for assessing population growth and protein productivity in mammalian cell culture. These methods were critically examined here, based on experiments with two hybridoma cell lines. It is shown that mammalian cell culture parameters must be evaluated on the same basis. In batch culture mode most data is obtained on a cumulative basis (protein product titre, substrate concentration, metabolic byproduct concentration). A simple numerical integration technique can be employed to convert cell concentration data to a cumulative basis (cell-hours). The hybridoma lines used in this study included a nutritionally non-fastidious line producing low levels of MAb and a nutritionally fastidious hybridoma with high productivity. In both cases the cell-hour approach was the most appropriate means of expressing the relationship between protein productivity and cell population dynamics. The cell-hour approach could be used as the basis for all metabolic population parameter evaluations. This method has the potential to be used successfully for both prediction and optimization purposes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A wild-type A. niger strain was employed as a model to investigate the effect of cell immobilization on extracellular protease secretion during fermentation. A metal-coated pad of polyester latex felt was used to immobilize the cells in shake flasks. Compared with free suspension culture, the maximum specific activity of the extracellular protease from immobilized cells was reduced from 129 units/g to 28 units/g. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 241-251 
    ISSN: 0006-3592
    Keywords: immobilization ; plasmid stability ; recombinant yeast ; glucoamylase, bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A recombinant Saccharomyces cerevisiae C468/pGAC9 (ATCC 20690), which expresses Aspergillus awamori glucoamylase gene under the control of the yeast enolase I (ENO1) promoter and secretes glucoamylase into the extracellular medium, was used as a model system to investigate the effect of cell immobilization on bioreactor culture performance. Free suspension cultures in stirred-tank and airlift bioreactors confirmed inherent genetic instability of the recombinant yeast. An immobilized-cell-film airlift bioreactor was developed by employing cotton cloth sheets to immobilize the yeast cells by attachment. Enhanced enzyme productivity and production stability in the immobilized-cell system were observed. Experimental data indicated that the immobilized cells maintained a higher proportion of plasmid-bearing cells for longer periods under continuous operation. The higher plasmid maintenance with immobilized cells is possibly due to reduced specific growth rate and increased plasmid copy number. Double-selection pressure was used to select and maintain the recombinant yeast. The selected strain showed better production performance than the original strain. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 241-251, 1997.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 62 (1995), S. 327-332 
    ISSN: 0268-2575
    Keywords: airlift reactor ; gas-liquid separator ; hydrodynamics ; oxygen transfer ; wastewater treatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three geometric configurations of gas-liquid separators were used in split-channel airlift reactors (0·1 m3 liquid volume; riser-to-downcomer cross-sectional area ratio = 0·7; aspect ratio = 3.6) to test the effect of geometry on hydrodynamic performance and oxygen transfer behaviour. For otherwise fixed conditions, the design of gas-liquid separators affected the induced liquid circulation rate, the depth of penetration of the bubble layer in the downcomer, the gas holdup in the downcomer, the mixing time and the overall volumetric gas-liquid oxygen transfer coefficient. The gas holdup in the riser was only marginally affected by the design of the separator. The impact of the various separator designs on hydrodynamic behaviour could be explained as emanating from a combination of the gas-liquid separating ability of the design and its hydraulic resistance.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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