Effects of pyruvate on primary metabolism and product quality for a high-density perfusion process.

High volumetric productivities can be achieved when perfusion processes are operated at high cell densities. Yet it is fairly challenging to keep high cell density cultures in a steady state over an extended period. Aiming for robust processes, cultures were operated at a constant biomass specific perfusion rate (BSPR) in this study. The cell density was monitored with a capacitance probe and a continuous bleed maintained the targeted viable cell volume. Despite our tightly controlled BSPR, a gradual accumulation of ammonium and changes in cell diameter were observed during the production phase for three different monoclonal antibodies. Although a lot of efforts in media optimization have been made to reduce ammonium in fed-batch process, less examples are known about how media components impact the cellular metabolism and thus the quality of monoclonal antibodies in continuous processes. In this study, we show that a continuous Na-pyruvate feed (2 g/L/day) strongly reduced ammonium production and stabilized fucosylation, sialylation and high mannose content for three different mAbs.