pH excursions impact CHO cell culture performance and antibody N-linked glycosylation

pH excursions exist due to frequent base addition and environmental heterogeneity in large-scale bioreactors. Such excursions could lead to suboptimal culture performance. Here we investigated the impact of pH excursions on cell culture performance and N-linked glycosylation for three MAb-producing Chinese hamster ovary cell lines. Frequent pH excursions were introduced by bolus base addition (in total 2-6% of initial volume, fixed bolus addition distributed from day 2 to 8) into small-scale bioreactors. Base addition led to increase in osmolality, pCO₂, and lactate production. Lactate production increase was mainly caused by increased culture pH due to base addition, and bolus addition led to higher glucose and lactate metabolic rates than continuous addition. For the three cell lines studied, antibody galactosylation increased with the increase in cultivating pH, correlating to the decrease in cell-specific productivity. Interestingly, pH excursions led to significantly higher galactosylation for one cell line, which also had a higher response to different cultivating pHs. On the other hand, there was no such substantial impact of pH excursions on galactosylation for the other two cell lines, both of which also had minimal response to cultivating pH. This suggests that the impact of pH excursions on antibody N-linked glycosylation is cell line specific and is closely related to cell line response to cultivating pH.