Scale‐down simulators for mammalian cell culture as tools to access the impact of inhomogeneities occurring in large‐scale bioreactors

Abstract

During the scale-up of a bioprocess, not all characteristics of the process can be kept constant throughout the different scales. This typically results in increased mixing times with increasing reactor volumes. The poor mixing leads in turn to the formation of concentration gradients throughout the reactor and exposes cells to varying external conditions based on their location in the bioreactor. This can affect process performance and complicate process scale-up. Scale-down simulators, which aim at replicating the large-scale environment, expose the cells to changing environmental conditions. This has the potential to reveal adaptation mechanisms, which cells are using to adjust to rapidly fluctuating environmental conditions and can identify possible root causes for difficulties maintaining similar process performance at different scales. This understanding is of utmost importance in process validation. Additionally, these simulators also have the potential to be used for selecting cells, which are most robust when encountering changing extracellular conditions. The aim of this review is to summarize recent work in this interesting and promising area with the focus on mammalian bioprocesses, since microbial processes have been extensively reviewed. K E Y W O R D S 2-compartment system, gradients, inhomogeneity, large-scale bioprocess, scale-upAbbreviations: CFD, computational fluid dynamics; CHO, Chinese Hamster ovary; CS, compartment system; PFR, plug flow reactor; STR, stirred tank reactor; VCC, viable cell count.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. throughput and decrease time lines for process development and characterization [1]. Particularly production processes for monoclonal antibodies (mAbs) that are in high demand, like adalimumab (Humira TM ) [2], are transferred to large-scale production reactors. These bioreactors can reach volumes of up to 25 000 L for mammalian cell culture processes [3]. Furthermore, it has been estimated that approximately 50% of the biologics will continue to be produced in bioreactor volumes of at least 5000 L [4]. There are different approaches Eng Life Sci.

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Growth and eGFP-production of CHO-K1 suspension cells cultivated from single-cell to lab-scale

“…The proven comparability between the microfluidic miniaturisation tool and shake flask or lab-scale bioreactor cultivation enables MSCC to be applied for numerous applications in basic research as well as for bioprocess development. In the context of mammalian bioproduction, especially studying cellular heterogeneity concerning growth behaviour and productivity inside isogenic populations is of utmost interest since it can have a severe influence on bioprocess robustness and outcome (Paul and Herwig 2020). Particularly the number of generations and the resulting cellular heterogeneity, with its effects from single-cell cloning up to commercially application, represents a very important question in process development (Frye et al 2016; Rugbjerg and Sommer 2019), that eventually can be analysed more closely by the means of MSCC.…”

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