Literature Sharing: Scale-Up and Scale-Down in Process Development

The development of a cell culture process begins with cell line establishment. At this stage, CHO cells are transfected with the target gene to create a stable transfected cell bank. Single cells are isolated from the stable cell pool, and production clones are selected based on growth and productivity characteristics, as well as product quality attributes. Traditionally, clone screening can be performed in simple small-scale culture systems such as shake flasks, static flasks, microtiter plates, or deep-well plates, typically with volumes below 20 mL.

With the increasing availability of well-equipped miniature bioreactors, plates and flasks are rapidly being replaced in many upstream development steps. Once a suitable production clone candidate is identified, process development progresses stepwise from laboratory to industrial-scale production (Figure 1).

Figure. 1. Cell Culture Process Development and Scale-Up (Image sourced from literature [1])

Process scale-up is a critical step, as challenges may arise during production-scale operations, including culture environment heterogeneity, dissolved CO₂ accumulation, and excessive shear stress due to aeration and mixing conditions. Ideally, these issues should be addressed and resolved during the pilot-scale stage before transitioning to commercial production. [1]Throughout cultivation, scale-up and scale-down models are employed for troubleshooting, process understanding, and optimization.

During scale-up, small-scale process performance must be maintained. Large-scale cell culture processes comprise multiple unit operations, including seed train expansion, inoculation, and production runs, each with critical performance indicators such as cell growth, viability, titer, and product quality attributes. Successful scale-up is typically measured by the consistency of these key indicators with predefined criteria.[1][2]

In bioreactor scale-up, agitation and aeration are two critical parameters that must be appropriately scaled to achieve comparable performance across different scales. Agitation is adjusted to ensure adequate mixing and oxygen mass transfer, often scaled using specific energy dissipation rate, while aeration is optimized for oxygen supply and CO₂ removal. CO₂ stripping depends on factors such as bicarbonate concentration, aeration and agitation rates, bubble size, and impeller type and positioning. In small-scale bioreactors, operational parameter ranges are typically broad, as mixing is rarely an issue even at low agitation speeds. Additionally, the higher surface-to-volume ratio facilitates efficient CO₂ removal. [2]In contrast, large-scale bioreactors require careful parameter selection due to increased shear stress (e.g., impeller tip speed) and CO₂ accumulation risks.

Beyond operational challenges, other common scale-up pitfalls include raw material batch-to-batch variability, medium preparation consistency, medium hold stability, and cell line stability during prolonged production. These issues can often be identified using scale-down models. A qualified scale-down model replicates large-scale performance at a smaller scale, providing critical insights for troubleshooting and process optimization. Beyond production support, such models are also used for process characterization and validation studies to define acceptable parameter ranges and identify critical process parameters.

Figure. 2. Operational Demo Diagram of CytoLinX® BR Single-Use Bioreactor

BioLink’s CytoLinX® BR Single-Use Bioreactor models cover volumes from 10 L to 2,000 L, addressing biopharmaceutical process needs with flexible customization options. Custom tank designs further support seamless scale-up. Leveraging extensive scale-up expertise, BioLink’s CytoLinX® GB Benchtop Glass Bioreactor (1 L to 20 L) meets small-scale cell culture requirements, replacing traditional shake flasks or wave bags with glass vessel cultivation. Scale-up parameters are optimized through iterative cultivation across varying glass vessel volumes.

BioLink CytoLinX® GB Benchtop Glass Bioreactor

 Figure. 3. CytoLinX® GB Benchtop Glass Bioreactor

Product Features:

· High Configurability: Exceptional flexibility with multiple options to streamline process development and characterization (custom glass tank volumes available for scale-up).

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· High Stability: Precise equipment control with integrated temperature, DO, and pH regulation.

· Multiple Sparging Options: Macro- and micro-bubble spargers available to meet diverse process needs.

BioLink CytoLinX® BR Single-Use Bioreactor

Figure 4. BioLink CytoLinX® BR Single-Use Bioreactor

Product Features:

· Optimized Tank Design: Fully functional with a single control cabinet supporting plug-and-play multi-tank management, reducing costs (custom tank volumes available for scale-up).

· Robust PCS7 System: Compliant with ISA 88 standards for full-plant control.

· 21 CFR Part 11-Compliant Software: Intuitive user interface.

· Flexible Customization: Partial customization based on user requirements.

· Premium Imported Components: High-end international brands, factory-tested for reliability.

· Single-Use Bioreactor Bag Compatibility: Macro-, medium-, and micro-bubble sparging options for diverse process needs.

References

[1] Lucas Lemire, Phuong Lan Pham, Yves Durocher, and Olivier Henry “Practical Considerations for the Scale-Up of Chinese Hamster Ovary (CHO) Cell Cultures”under exclusive license to Springer Nature Switzerland AG 2021 R. Pörtner (ed.), Cell Culture Engineering and Technology, Cell Engineering 10, https://doi.org/10.1007/978-3-030-79871-01_2

[2] Feng Li,1 Natarajan Vijayasankaran,Amy(Yijuan) Shen, Robert Kiss, and Ashraf Amanullah , Cell culture processes for monoclonal antibody production,2010 Sep-Oct; 2(5): 466–477.doi: 10.4161/mabs.2.5.12720  MAbs.