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Abstract BACKGROUND The determination of the residence time distribution of an entire process or process step in integrated continuous biomanufacturing is required for process understanding, traceability determination and to efficiently handle process disturbances. When recombinant proteins such as monoclonal antibodies are captured by continuous precipitation and two‐stage filtration, the question arises whether simple salt is suitable as a tracer or whether a labeled protein is required. RESULTS We have investigated the use of various inert tracers, sodium nitrate (NaNO 3 ) due to its absorbance at UV 280 nm, and fluorescently labeled or unlabeled antibodies to determine the RTD of the product at steady‐state and in the start‐up and shut‐down phases. All tracers are suitable for measuring the RTD of the precipitated antibody for individual unit operations. For interconnected unit operations, if the product is concentrated, the RTD can be determined with labeled or unlabeled antibodies, because it is not possible to concentrate salts in a microfiltration unit. The duration of the start‐up and shut‐down phases depends on the concentration factor applied in two‐stage filtration, and the number of reactor volumes required to reach steady state corresponds to the concentration factor. Around 1.6 reactor volumes are required for the shutdown phase for 99% wash‐out. CONCLUSION The integrated process has a plug flow characteristic, which is advantageous as the process can react quickly when process deviations occur. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).
Recanati et al. (Fri,) studied this question.