A real-time oxygen uptake rate monitoring approach suitable for the antibody production process

Significant progress has been achieved in large-scale mammalian cell culture technology for biotherapeutics manufacturing over the past decades, necessitating the Process Analytical Technology (PAT) for the real-time measurement of critical quality attributes and the guidance for precise process control to ensure productivity, quality, and consistency. The Oxygen Uptake Rate ($\mathrm{OUR}$) serves as a crucial indicator for characterizing the energy metabolism of mammalian cells, offering insights into cellular state and metabolism dynamics. However, current cellular $\mathrm{OUR}$ monitoring in antibody production depends mainly on costly gas analyzers or periodic manual sampling. Here, we introduce a novel method for in-line monitoring of cellular $\mathrm{OUR}$ in bioreactors based on the stationary liquid phase balance (SLPB) theory, which extends its applicability to diverse aeration and foam conditions without additional equipment or labor expenditures. We modeled the $k_{L}a$ of the aerated stirred bioreactor, assessed the influence of foam on liquid surfaces induced by gas sparging on oxygen transfer, and processed raw $\mathrm{OUR}$ data using a sliding filter. The established method was applied to monitoring the real-time $\mathrm{OUR}$ of Chinese Hamster Ovary (CHO) cell cultures for antibody production, demonstrating its excellent accuracy, sensitivity and readability. Aligned with the Quality by Design (QbD) concept, this real-time $\mathrm{OUR}$ estimation enables rapid detection of metabolic changes, revealing cellular physiology and facilitating precise feedback control in biotherapeutics manufacturing.