Spectroscopic sensors are powerful tools for bioprocess monitoring within the process analytical technology (PAT) initiative of the US Food and Drug Administration (FDA). The PAT framework includes process understanding based on scientific background with the aim of monitoring and controlling critical process parameters (CPPs) that influence critical quality attributes (CQAs) of final biological products. The driving force for PAT implementation is a need to realize consistent product quality, process intensification, and real-time manufacturing control (1, 2). Using real-time spectroscopic measurements…