By John Longsworth, Nina Schillings, and Ma Sha
Eppendorf bioprocess controllers, such as the BioFlo® 320 Bioreactor Control System, use a proportional– integral–derivative (PID) control mechanism for a variety of processes, including dissolved oxygen (DO) control. The PID control loop mechanism for DO control is essential for optimal bioreactor cell culture. Although the D value is not user adjustable in Eppendorf controllers, the P and I values can be changed. The default P and I values set on the controller are good starting points but may not be optimal for specific cell culture processes or vessels.
This protocol introduces a method developed at the Eppendorf bioprocess applications lab to optimize the PI values on Eppendorf bioprocess controllers, including the BioFlo 320. The method is based on pre-programmed delivery of chemical oxygen scavengers to accurately simulate the oxygen demand throughout a bioreactor cell culture process. This chemical simulation allows for quick and accurate tuning of PI values for cell culture DO control. The method can be adopted to fermentation PI tuning as well. However, a more aggressive gassing demand model will need to be established by the user to match the actual gassing demand for fermentation processes.