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  • 11
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    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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  • 14
    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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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Current microbiology 10 (1984), S. 265-268 
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Aspartate, glutamate, or dicarboxylic acids did not inhibit the activity of a highly purified but not homogeneous preparation of pyruvate carboxylase fromThiobacillus novellus. The only effective inhibitors were end-products of the reaction and to a lesser degree hydroxypyruvate. The latter has not been shown previously to regulate the enzyme's activity. Lineweaver-Burk plots revealed that it was uncompetitive with respect to acetyl CoA with a Kii of 3.6 mM, and noncompetitive with respect to bicarbonate, magnesium ATP, and pyruvate with respective Kii values of 7.1, 5.5, and 6.47 mM. The corresponding Kis values were 7.02, 5.4, and 4.25 mM. A mathematical model is presented that supports the findings.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 314-319 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methanogenesis was studied in downflow stationary fixed-film bioreactors. The support materials in this study included ceramic Raschig rings, hardwood chips, and sized charcoal. The performances of these support materials have been compared using both synthetic acid mixture and acid products obtained from paper mill sludge. Woodchips appeared to be the most promising support material: The maximum methane productivity of 3.56 L/L day at a nominal retention time of 0.78 day was obtained using initial total acid concentrations of 9.125 g/L. Higher productivity was achieved at the cost of efficiency of the process in terms of conversion of acids. From nitrogen balances, it was deduced that ammonia supplemented methane generation by supplying hydrogen for there duction of carbon dioxide.An ionic balance was developed to ascertain the relationship between the composition and the pH of the liquid and the mole fraction of carbon dioxide in the gas phase. From these ionic balance equations, it was possible to predict the gas phase composition at various retention times. The maximum error between the computed and the experimental values was less than 13%.
    Additional Material: 2 Ill.
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  • 17
    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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