Upstream bioprocessing in perfusion mode holds great promise for industrial production of cells and biologics. In perfusion, fresh medium is added constantly to the bioreactor, and used medium is harvested while the cells are retained in the bioreactor. As a result, the composition of the cell culture medium stays quite constant during the process. This offers several advantages. In perfusion, higher cell densities can be reached than in batch and fed-batch processes, therefore enhancing volumetric productivity. Because medium composition can…