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  • 1
    Electronic Resource
    Electronic Resource
    Perfusion-microcarrier cultivation of rCHO-cells in serum-free medium for production of human renin (1991)
    Springer
    Bioprocess and biosystems engineering 7 (1991), S. 63-69 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A recombinant CHO cell line producing human prorenin was cultivated on microcarriers in serum-free medium. Best growth was obtained when the cells were cultivated on a collagen coated microcarrier (Cytodex 3) using a serum-free medium (SF-02) supplemented with fibronectin. It was possible to reduce the necessary concentration of fibronectin in the feed medium from 10 μg/cm3 to 2 μg/cm3 during perfusion cultures in a spinner reactor equipped with an UF-membrane. Also in this system, the prorenin concentration increased up to 8 times higher compared to that in a conventional repeated-batch culture. The cells grew in multilayers on the microcarriers during the perfusion culture. The specific prorenin productivity was not significantly affected by the cell growth rate, and the secretion of prorenin continued even after the cells had ceased to grow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383580
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    High density fed-batch cultures for hybridoma cells performed with the aid of a kinetic model (1996)
    Springer
    Bioprocess and biosystems engineering 15 (1996), S. 117-124 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridoma fed-batch cultures with either standard medium as feed or concentrated medium as feed and removal of toxic metabolites through dialysis were performed by using model calculations for “a priori” determination of process parameters. In a first step a kinetic model for specific growth and death rate, respectively as well as for substrate uptake and metabolite production rates was formulated. In a bed-batch culture with standard medium as feed the appropriate time for start of the feeding pump and the increase of feed rate were determined “a priori”. The glutamine concentration was controlled at 0.04 mmoll−1. “A priori” calculation and course of the culture coincided rather well. A cell concentration of 3.2×106 cells ml−1, a MAb-concentration of 54 mg MAb l−1 and a MAb-time-space-yield of 0.53 mg MAb l−1h−1 were obtained. For further increase of the efficiency a high density fed-batch process was developed, where concentrated medium is fed to the cells and the accumulating toxic low molecular weight metabolites are removed through a dialysis membrane into a dialyizng fluid. In a membrane dialysis reactor consisting of a culture chamber and a dialyzing chamber, which are separated by a cylindrical dialysis membrane, again model calculations were used to determine feed rate and exchange rate of dialyzing fluid. A viable cell density of 1.2×107 cells ml−1 and a MAb concentration of 425 mg l−1 were reached in a culture with stepwise feeding of 10 x concentrated medium and exchange of dialyzing fluid for removal of low molecular metabolites. The course of the culture could be predicted “a priori” rather well. The MAb-time-space-yield was 2.47 mg MAb l−1h−1, appr. 5 times higher compared to fed-batch cultures with standard medium as feed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369614
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  • 3
    Electronic Resource
    Electronic Resource
    Cartilage Cultivation on a Calcium Phosphate Ceramic in a Bioreactor System (2004)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 264-268 (May 2004), p. 2119-2122 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/48/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.264-268.2119.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Performance of a membrane-dialysis bioreactor with a radial-flow fixed bed for the cultivation of a hybridoma cell line (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 772-780 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A bioreactor system for the continuous cultivation of animal cells with a high potential for scale-up is presented. This reactor system consists of radial-flow fixed-bed units coupled with a dialysis module. The dialysis membrane enables the supply of low-molecular-weight nutrients and removal of toxic metabolites, while high-molecular-weight nutrients and products (e.g. monoclonal antibodies) are retained and accumulated. This concept was investigated on the laboratory scale in a bioreactor with an integrated dialysis membrane. The efficiency of the reactor system and the reproducibility of the cell activity (hybridoma cells) under certain process conditions could be demonstrated in fermentations up to 77 days. Based on model calculations, an optimized fermentation strategy was formulated and experimentally confirmed. Compared to chemostat cultures with suspended cells, a ten-times higher mAb concentration (383 mg l-1) could be obtained. The highest volumetric specific mAb production rate determined was 6.1 mg mAb (l fixed bed)-1 h-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050484
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  • 5
    Electronic Resource
    Electronic Resource
    Performance of a membrane-dialysis bioreactor with a radial-flow fixed bed for the cultivation of a hybridoma cell line (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 772-780 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A bioreactor system for the continuous cultivation of animal cells with a high potential for scale-up is presented. This reactor system consists of radial-flow fixed-bed units coupled with a dialysis module. The dialysis membrane enables the supply of low-molecular-weight nutrients and removal of toxic metabolites, while high-molecular-weight nutrients and products (e.g. monoclonal antibodies) are retained and accumulated. This concept was investigated on the laboratory scale in a bioreactor with an integrated dialysis membrane. The efficiency of the reactor system and the reproducibility of the cell activity (hybridoma cells) under certain process conditions could be demonstrated in fermentations up to 77 days. Based on model calculations, an optimized fermentation strategy was formulated and experimentally confirmed. Compared to chemostat cultures with suspended cells, a ten-times higher mAb concentration (383 mgl−1) could be obtained. The highest volumetric specific mAb production rate determined was 6.1 mg mAb (1 fixed bed)−1 h−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02431907
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Dialysis cultures (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 403-414 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Dialysis techniques are discussed as a means for effective removal of low-molecular-mass components from fermentation broth to reach high cell density. Reactor systems and process strategies, the relevant properties of membranes and examples for high-density fermentation with dialysis, and problems related to scale-up are addressed. The dialysis technique has turned out to be very efficient and reliable for obtaining high cell densities. As in dialysis processes the membranes are not perfused, membrane clogging is not a problem as it is for micro- and ultrafiltration. By applying a “nutrient-split” feeding strategy, the loss of nutrients can be avoided and the medium is used very efficiently. The potential of dialysis cultures is demonstrated on the laboratory scale in a membrane dialysis reactor with an integrated membrane and in reactor systems with an external dialysis loop. In dialysis cultures with different microorganisms (Staphylococci, Escherichia coli, extremophilic microorganisms, Lactobacilli) the cell densities achieved were up to 30 times higher than those of other fermentation methods. The technique enables high cell densities to be attained without time-consuming medium optimization. For animal cell cultures the concept of a fixed bed coupled with dialysis proved to be very effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051312
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  • 7
    Electronic Resource
    Electronic Resource
    Fixed-bed dialysis culture of a transfectoma cell line producing chimeric Fab-fragments with “nutrient-split”-feeding strategy (1998)
    Springer
    Biotechnology techniques 12 (1998), S. 501-505 
    Details
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The very shear sensitive transfectoma cell line, FAB 10, producing a chimeric Fab-antibody fragment specific for the human carcinoembryonic antigen (CEA), was cultivated in fixed bed reactors where the cells were immobilized in macroporous carriers. As the cell line had a very low productivity, cultures with “process integrated product enrichment” were performed in a membrane dialysis bioreactor with integrated fixed bed, where low molecular weight metabolites are removed over the membrane and high molecular weight products are enriched. In a new “nutrient-split” feeding strategy for dialysis cultures concentrated medium was supplied directly to the fixed bed unit, whereas a buffer solution was used as dialysis fluid. With the dialysis technique up to 5800 μg Fab l−1 could be obtained, more than 10 times higher compared to fixed bed cultures without dialysis or batch cultures with suspended cells. The “nutrient-split”-feeding strategy reduced the amount of medium required per mg of antibody significantly. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008839127835
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Bcl-2 Expression on Hybridoma Cell Growth in Serum-Supplemented, Protein-Free and Diluted Media (1998)
    Springer
    Cytotechnology 26 (1998), S. 219-225 
    Details
    ISSN: 1573-0778
    Keywords: apoptosis ; Bcl-2 ; diluted medium ; hybridoma ; protein-free medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two transfected hybridoma cell lines TB/C3-bcl2 (overexpressing the Bcl-2 protein) and TB/C3-pEF (control cell line), were compared in batch suspension cultures using a medium supplemented either with horse serum or with a protein-free, iron-rich supplement. The membrane intact index (percentage of cells with intact membranes determined by trypan blue staining) of the TB/C3-bcl2 cell line decreased much slower than that of the control cell line during the dying phase of the cultures. No significant difference in antibody, lactate and ammonia production as well as glucose and glutamine consumption was noted in the exponential phase of the experiments. Both cell lines were also compared in batch experiments using media diluted with saline to further investigate the effect of Bcl-2 under sub-optimal conditions. The Bcl-2 overexpressing cell line again exhibited a higher membrane intact index at increasing dilution steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007914619219
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  • 9
    Electronic Resource
    Electronic Resource
    A model for oxygen supply in fixed bed reactors with immobilized hybridoma cells (1997)
    Springer
    Bioprocess engineering 17 (1997), S. 269-275 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  In fixed bed reactors with animal cells immobilized in macroporous carriers sufficient oxygen supply is a critical parameter. For modelling of the oxygen consumption and the oxygen profile in a fixed bed oxygen gradients within the porous carriers and along the length of the fixed bed have to be considered. For the complex geometry of the fixed bed a model structure was assumed, that allows the calculation of the oxygen profile. The model for oxygen supply of the immobilized cells included the transport resistance from the bulk fluid into the carriers and diffusion within the carriers. The model was compared with experimental data obtained with a hybridoma cell line for production of monoclonal antibodies. Model calculations and experimental data agree rather well. The mean volume-specific oxygen uptake rate as an indicator for the cell activity increased with the superficial flow velocity of the bulk liquid flow, and did not depend on the length of the fixed bed in the range tested. This indicates, that the convective transport from the bulk liquid flow between the carriers to the outer surface of the carriers is a dominating transport resistance besides the diffusive oxygen supply within the carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004490050385
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  • 10
    Electronic Resource
    Electronic Resource
    High density fed-batch cultures for hybridoma cells performed with the aid of a kinetic model (1996)
    Springer
    Bioprocess engineering 15 (1996), S. 117-124 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Hybridoma fed-batch cultures with either standard medium as feed or concentrated medium as feed and removal of toxic metabolites through dialysis were performed by using model calculations for “a priori” determination of process parameters. In a first step a kinetic model for specific growth and death rate, respectively as well as for substrate uptake and metabolite production rates was formulated. In a bed-batch culture with standard medium as feed the appropriate time for start of the feeding pump and the increase of feed rate were determined “a priori”. The glutamine concentration was controlled at 0.04 mmol l-1. “A priori” calculation and course of the culture coincided rather well. A cell concentration of 3.2 * 106 cells ml-1, a MAb-concentration of 54 mg MAb  l-1 and a MAb-time-space-yield of 0.53 mg MAb  l-1 h-1 were obtained. For further increase of the efficiency a high density fed-batch process was developed, where concentrated medium is fed to the cells and the accumulating toxic low molecular weight metabolites are removed through a dialysis membrane into a dialyzing fluid. In a membrane dialysis reactor consisting of a culture chamber and a dialyzing chamber, which are separated by a cylindrical dialysis membrane, again model calculations were used to determine feed rate and exchange rate of dialyzing fluid. A viable cell density of 1.2 * 107 cells ml-1 and a MAb concentration of 425 mg l-1 were reached in a culture with stepwise feeding of 10×concentrated medium and exchange of dialyzing fluid for removal of low molecular metabolites. The course of the culture could be predicted “a priori” rather well. The MAb-time-space-yield was 2.47 mg MAb  l-1 h-1, appr. 5 times higher compared to fed-batch cultures with standard medium as feed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369614
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    Paper (German National Licenses)
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