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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1133-1140 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to develop an efficient process for large-scale production of recombinant protein, various factors were studied which affect the productivity of Sf-9 (Spodoptera frugiperda) insect cells when using the baculovirus expression system. It was shown that upon infection with the Bac-BRV6L recombinant baculovirus, the level per cell of VP6 (a bovine rotavirus nucleocapsid protein) would drop 10-fold when host cell density at the time of infection increased from 2 × 106 to 3 × 106 cells/mL. The decrease was found to be totally reversible by culture medium renewal after infection, even when cells were infected at the stationary phase. Recombinant protein production was 4-6 times higher using TNMFH medium supplemented with 10% fetal bovine serum (FBS) than in IPL/41 serum-free medium. Fine-tuning of infection parameters in a 4-L surface-aerated bioreactor resulted in the production of typically 350 mg/L of VP6 protein, representing more than 25% of total cell proteins.
    Additional Material: 6 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 38 (1991), S. 781-787 
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; continuous culture ; cell cycle ; tangential filtration ; cell separation ; nuclepore membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/109 cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar “grow or die” life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 833-846 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this study, a filtration-based perfusion process was developed for the production of monoclonal antibodies (IgM) by suspended hybridoma cells grown in protein-free medium. It was found that the use of protein-free medium for perfusion culture generated the formation of numerous visible suspended particles consisting of dead cells and cellular debris aggregated into fibrous material. Surprisingly high apparent viabilities were observed in such protein-free cultures. In addition, membrane fouling occurred more rapidly in protein-free medium than in conventional serum-supplemented medium. By the addition of deoxyribonuclease I (DNase I) to the protein-free medium, it was possible to prevent the formation of aggregates and to follow the evolution of the total cell population more accurately. Moreover, DNase I significantly reduced the fouling of filtration membranes, and that, for two different types of separation systems (cross-flow and vortex-flow filtration) and two different types of membranes (polycarbonate and hydrophilized polysultone). From these results, it is clear that the presence of DNA fragments liberated following cellular death is playing an important role in membrane fouling. Longevity of filtration membranes was found to be considerably greater using a vortex-flow filtration module than with a static plate-and-frame cross-flow filtration module. The use of vortex-flow filtration of conjuction with DNase I allowed maintenance of perfusion cultures for more than 1 month without membrane fouling or antibody retention and with a constant permeate IgM concentration of 250 mg/L. Hybridomacells appeared to gradually adapt to increasing rotational speed in the vortex-flow filtration module.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 881-891 
    ISSN: 0006-3592
    Keywords: baculovirus ; recombinant proteins ; Sf-9 insect cells ; perfusion ; tangential filtration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A perfusion system based on a 4-L stirred tank bioreactor and a custom-designed tangential (cross-flow) filter was assembled to realize a scaleup of the Baculovirus Expression Vector System (BEVS). When perfused with 1 to 1.5 vol/day, Spodoptera frugiperda (Sf-9) insect cell cultures grew from 4 × 106 to 15 × 106 cells/mL over 3 to 4 days. The possibility of maintaining high specific production of recombinant VP6 protein (from bovine rotavirus) after baculovirus infection of the high-density cultures was then assessed. The process consisted of a growth phase in TNMFH + 10% FBS, followed by infection with Bac-BRV6L recombinant baculovirus and a shift to a low-serum (0 to 1%) medium for perfusion during the production phase. Multiple runs were executed, each including a battery of shaker flask controls at various cell densities and serum concentrations. On average, specific rVP6 production in the bioreactor amounted to 76% of that found in 20-mL shaker cultures simulatingthe bioreactor's high cell density, low serum concentration, and medium renewal rate. Mechanical stress generated by cell/medium separation in theperfusion process reduced cell growth rate but had minimal effect on rVP6production. Our results also indicated that serum concentration during the infection phase affected the rVP6 specific production in a cell density-dependent fashion. Although the feasibility of the cell density scale up was demonstrated, optimization is still needed to achieve a truly cost-effective process.
    Additional Material: 4 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 44 (1994), S. 1140-1154 
    ISSN: 0006-3592
    Keywords: ammonia ; apoptosis ; hybridoma ; lactate ; myeloma ; nutrient deprivation ; programmed cell death ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, cell death was investigated in cultures of NS/0 myelomas and SP2/0-derived D5 hybridomas through morphological examination of cells stained with acridine orange and ethidium bromide. The relative contribution of elevated levels of lactic acid and ammonia, as well as deprivation of glutamine, cystine, and glucose on the induction of necrosis or apoptosis, was investigated. In batch culture of D5 hybridoma cells, induction of apoptotic cell death correlated with the exhaustion of glutamine, while in the case of NS/0 myelomas, it coincided with exhaustion of cystine. To determine whether limiting nutrients were the actual triggering factors for apoptosis in batch culture, exponentially growing cells were resuspended in glutamine or cystine-free media. Within 30 to 40 h, viability decreased to 50% and the nonviable cell population displayed typical apoptotic morphology, with crescents of condensed chromatin around the periphery of the nucleus, or with the entire nucleus present as one or a group of featureless, brightly staining spherical beads. Similarly, D5 hybridomas and NS/0 myelomas cultivated in glucose-free medium died mainly from apoptosis. Cells were also cultivated in fresh medium supplemented with elevated concentrations of ammonia (3.0 mM) and/or lactate (35 mM, 50 mM). This resulted in decreased viabilities and necrotic death in both cell lines. From these results, we conclude that D5 hybridomas and NS/0 myelomas deprived of essential nutrients die by apoptosis, whereas incubation in the presence of elevated levels of metabolic byproducts such as ammonia and lactate will induce necrotic cell death in these cells. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 25-32 
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; tangential filtration ; cell separation ; Nucleopore membranes ; alginate beads ; hollowfiber bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The efficiency of lgM production by hybridoma cells (1) cultured in suspension; (2) entrapped in alginate beads; or (3) packed in hollowfiber cartridge bioreactors, were compared in long-term perfusion cultures. The results showed that steady-state cell concentration and antibody production, per liter of perfused medium per day, were similar when cells were either entrapped in alginate beads of maintained in suspension. These values were also similar whether cells were maintained at high density in a hollowfiber cartridge bioreactro, or at low density in suspension. This work points out that cell behavior and antibody yield are comparable overall in the various perfusion systems currently used. However, a significant reduction of antibody production appeared whenever a part of the viable cells was lost in the filtrate. The reduction was due both to a decrease of viable cell yield and a decline of lgM productivity on a percell basis. This result is well in agreement with the previously presented model of “grow or die” cell cycle system of hybridoma, which proposes that the ratio of arrested to proliferating cells in perfusion cultures, should be increased in proportion to cell retention in the bioreactor, with a concomitant increase of lgM productivity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 567-575 
    ISSN: 0006-3592
    Keywords: adenovirus ; adenoviral vectors ; 293 cells ; recombinant proteins ; serum-free medium ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes the step-wise approach undertaken to select a serum-free medium (SFM) for the efficient production of a recombinant adenoviral vectors expressing β-galactosidase (Ad5 CMV-LacZ), in the complementing human embryonic kidney 293S cells. In the first step, a 293S-derived transfectoma, secreting a soluble epidermal growth factor receptor sEGFr (D2-22), was used to estimate the potential of selected serum-free formulations to support the production of a recombinant protein as compared to serum-containing medium. Assays showed that only one among six commercial serum-free formulations could support both sEGFr production and cell growth in static or suspension culture. In commercially available calcium-containing serum-free formulations, the cell aggregates reached up to 3 mm in diameter. In the second step, 293S cells were gradually adapted to a low-calcium version of the selected medium (LC-SFM). Cells were cloned, then screened according to their ability to grow at a rate and an extent comparable to parental cells in serum-containing medium (standard) as single cells or small aggregates. The 293SF-3F6 clone, first adapted to and then cloned in the selected serum-free medium, was selected for further experiments. Bioreactor run performed with the 293SF-3F6 clone showed similar growth curve as in the shake-flask controls. In the final step, the recombinant viral vector productivity of the 293S cells and the 293SF-3F6 clone was tested. The 293SF-3F6 cells infected by Ad5 CMV-LacZ in 3 L-scale bioreactor maintained the specific productivities of both β-galactosidase and adenoviral vector equivalent to the shake-flask controls in suspension culture. Results from this study clearly demonstrate that the 293SF-3F6 cell line thus selected may be used either for establishing stable transfected cell line or for the production of adenoviral vectors required for gene therapy studies. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 567-575, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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