Assessment of fed-batch cultivation strategies for an inducible CHO cell line

In order to maximize cell growth and productivity for an inducible CHO cell line expressing rituximab, various fed-batch culture strategies were investigated. In each case, the performance was evaluated for cultures induced at moderate and high cell density conditions (4 × 10⁶ and 10 × 10⁶ cells/mL) to assess the impact of the timing of induction. We first demonstrate the importance of starting the feeding process during the growth phase, as this translated into significantly improved integral of viable cells and antibody concentration, when compared to post-induction feeding only. Secondly, we investigated the impact of the feed rate by maintaining different levels of glucose (25, 35 and 50 mM) via a dynamic feeding strategy. The highest antibody concentrations were achieved under a moderate feeding regime for both cell densities at induction, highlighting the risks of under- or over-feeding the cultures. We then evaluated the impact of performing a temperature shift at induction by testing different mild hypothermia conditions. At small-scale, the highest production yields (1.2 g/L) were achieved when the temperature was reduced from 37 to 30 °C during the production phase of a culture induced at high cell density. When the strategy was applied in bioreactor, the better controlled conditions led to even greater product concentrations (1.8 g/L). Furthermore, this production protocol was shown to promote a more galactosylated glycan profile than a bioreactor culture initiated at 34 °C during growth and downshifted to 30 °C during the production phase.