Validation of a CFD model for cell culture bioreactors at large scale and its application in scale-up

• Published in: Journal of biotechnology 2024-05, Vol.387, p.79-88
• Main Authors: Xing, Zizhuo, Duane, Gearóid, O’Sullivan, Josiah, Chelius, Cynthia, Smith, Laura, Borys, Michael C., Khetan, Anurag
• Format: Article
• Language: English
• Subjects: aeration; agitation; air flow; Animals; Bioreactors; carbon dioxide; Carbon Dioxide - metabolism; Carbon dioxide stripping; cell culture; Cell Culture Techniques - instrumentation; Cell Culture Techniques - methods; CHO Cells; commercialization; Computational fluid dynamics; Computer Simulation; Cricetulus; Gas entrance velocity; Hydrodynamics; Impeller flooding; impellers; model validation; Models, Biological; oxygen; Oxygen - analysis; Oxygen - metabolism; Oxygen demand model; Process scale-up; Volumetric oxygen transfer coefficient
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2024.02.006

Among all the operating parameters that control the cell culture environment inside bioreactors, appropriate mixing and aeration are crucial to ensure sufficient oxygen supply, homogeneous mixing, and CO2 stripping. A model-based manufacturing facility fit approach was applied to define agitation and bottom air flow rates during the process scale-up from laboratory to manufacturing, of which computational fluid dynamics (CFD) was the core modeling tool. The realizable k-ε turbulent dispersed Eulerian gas-liquid flow model was established and validated using experimental values for the volumetric oxygen transfer coefficient (kLa). Model validation defined the process operating parameter ranges for application of the model, identified mixing issues (e.g., impeller flooding, dissolved oxygen gradients, etc.) and the impact of antifoam on kLa. Using the CFD simulation results as inputs to the models for oxygen demand, gas entrance velocity, and CO2 stripping aided in the design of the agitation and bottom air flow rates needed to meet cellular oxygen demand, control CO2 levels, mitigate risks for cell damage due to shear, foaming, as well as fire hazards due to high O2 levels in the bioreactor gas outlet. The recommended operating conditions led to the completion of five manufacturing runs with a 100% success rate. This model-based approach achieved a seamless scale-up and reduced the required number of at-scale development batches, resulting in cost and time savings of a cell culture commercialization process. [Display omitted] •Appling a bioprocessing model package in manufacturing facility fit.•Predicting impeller flooding of a scale-up model by computational fluid dynamics.•Predicting pCO2 levels by CO2 stripping model.•Evaluating cellular oxygen demand, foaming, and fire hazards.•Achieving seamless scale-up with reduced manufacturing scale development batches.