Development of a Scale-Down Model of hydrodynamic stress to study the performance of an industrial CHO cell line under simulated production scale bioreactor conditions.

The objective of this study was to develop a Scale-Down Model of a hydrodynamic stress present in large scale production bioreactors to investigate the performance of CHO cells under simulated production bioreactor conditions. Various levels of hydrodynamic stress were generated in 2L bioreactors mimicking those present in different locations of a large scale stirred tank bioreactor. In general, it was observed that tested cells are highly robust against the effect of hydrodynamic stress. However, at elevated hydrodynamic stress equivalent to an average energy dissipation rate, ε, equal to 0.4W/kg, the specific monoclonal antibody productivity, qmAb, decreased by 25% compared to the cultivation conditions corresponding to ε equal to 0.01W/kg. Even stronger decrease of qmAb, in the order of 30%, was observed when ε was periodically oscillating between 0.01 and 0.4W/kg to simulate the repeated passage of cells through the highly turbulent impeller discharge zone of a production scale bioreactor. Despite this effect, no changes in metabolite consumption or byproduct formation were observed. Furthermore, considering the experimental error product quality was independent of the applied ε. To achieve a molecular insight into the observed drop of cellular productivity, a transcriptome analysis using mRNA microarrays was performed. It was found that transcripts related to DNA damage and repair mechanisms were upregulated when high ε was applied for cultivation.