Scale-Up analysis for a CHO cell culture process in large-scale bioreactors

Process Sciences, Biologics Manufacturing and Process Development, Worldwide Medicines Group, Bristol-Myers Squibb Company, Syracuse, NY 13221-4755, USA.
Biotechnology and Bioengineering (Impact Factor: 4.13). 07/2009; 103(4):733-46. DOI: 10.1002/bit.22287
Source: PubMed

ABSTRACT Bioprocess scale-up is a fundamental component of process development in the biotechnology industry. When scaling up a mammalian cell culture process, it is important to consider factors such as mixing time, oxygen transfer, and carbon dioxide removal. In this study, cell-free mixing studies were performed in production scale 5,000-L bioreactors to evaluate scale-up issues. Using the current bioreactor configuration, the 5,000-L bioreactor had a lower oxygen transfer coefficient, longer mixing time, and lower carbon dioxide removal rate than that was observed in bench scale 5- and 20-L bioreactors. The oxygen transfer threshold analysis indicates that the current 5,000-L configuration can only support a maximum viable cell density of 7 x 10(6) cells mL(-1). Moreover, experiments using a dual probe technique demonstrated that pH and dissolved oxygen gradients may exist in 5,000-L bioreactors using the current configuration. Empirical equations were developed to predict mixing time, oxygen transfer coefficient, and carbon dioxide removal rate under different mixing-related engineering parameters in the 5,000-L bioreactors. These equations indicate that increasing bottom air sparging rate is more efficient than increasing power input in improving oxygen transfer and carbon dioxide removal. Furthermore, as the liquid volume increases in a production bioreactor operated in fed-batch mode, bulk mixing becomes a challenge. The mixing studies suggest that the engineering parameters related to bulk mixing and carbon dioxide removal in the 5,000-L bioreactors may need optimizing to mitigate the risk of different performance upon process scale-up.

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    • "Among the cell lines available for mAb production are myeloma, hybridoma, and Chinese hamster ovary (CHO) cell lines [3,4]. The use of CHO cells in large-scale production is common [3,5-7] because of their ability to express high recombinant protein levels [8,9], grow to high cell densities [10-13], and to grow in serum-free suspension culture [6,14-16]. CHO cells are also suitable for use with expression systems, such as dihydrofolate reductase (DHFR) and glutamine synthetase (GS) [17-19]. "
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    • "A practical explicit formula is (4) where H 2 O is the concentration of water in the liquid phase, He C Henry's constant for CO 2 , p the actual total pressure and y C the molar fraction of CO 2 in the gas phase. In literature (e.g., Xing et al. [12]), y C is most often assumed to be the carbon dioxide concentration in the air pressed into the sparger and that is the very problem. Due to mass transfer across the bubble interfacial area, A B , changes in the amount n C of CO 2 within a single representative gas bubble along its path in the continuous liquid phase can be described by the simple ordinary differential equation in n C (5) which can easily be derived from Eq. (1). "
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    • "Mammalian cell cultures are a predominant vehicle for the production of proteins at an industrial scale. Production methods range from transient, but large-scale, high efficiency transfections of cell cultures [1–3] to the establishment of stable cell lines that are subsequently grown in large-scale reactors [4, 5]. In the last case, identification of clones that couple high protein expression to good growth conditions is pivotal. "
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