Applications of off-gas mass spectrometry in fed-batch mammalian cell culture

Hai-Yuan Goh,Graham D Josland,Graham L Lewis,Daniel E Merriman,Haneen Alosert,Michael Sulu

doi:10.1007/s00449-019-02242-2

Abstract

Off-gas analysis using a magnetic sector mass spectrometer was performed in mammalian cell cultures in the fed-batch mode at the 5 L bench and 50 L pilot scales. Factors affecting the MS gas traces were identified during the duration of the fed-batch cultures. Correlation between viable cell concentration (VCC) and oxygen concentration of the inlet gas into the bioreactor (O2-in) resulted in R2 ≈ 0.9; O2-in could be used as a proxy for VCC. Oxygen mass transfer (kLa) was also quantified throughout the culture period with antifoam addition at different time points which is shown to lower the kLa. Real-time specific oxygen consumption rate (qO2) of 2–20 pmol/cell/day throughout the bioreactor runs were within the range of values reported in literature for mammalian cell cultures. We also report, to our knowledge, the first instance of a distinct correlation between respiration quotient (RQ) and the metabolic state of the cell culture with regard to lactate production phase (average RQ > 1) and consumption phase (average RQ < 1).

Highlights

Process analytical technology (PAT) is used by biopharmaceutical companies to ensure that product quality is maintained, defined by the process’ critical quality attributes, CQAs
It should be noted that while no control loop with respect to the mass spectrometry (MS) gas traces was applied in these experiments, observations were made on the MS gas traces during the fed-batch bioreactor runs
While the exact components of the feed media were not known publicly as it was a proprietary media, it was believed that EfficientFeedTM B contained surfactants, like Pluronic, and possibly other compounds that had a direct impact on the kLa

Summary

Introduction

Process analytical technology (PAT) is used by biopharmaceutical companies to ensure that product quality is maintained, defined by the process’ critical quality attributes, CQAs. The use of paramagnetic and zirconium dioxide sensors for oxygen concentration determination and infra-red sensor for carbon dioxide concentration determination had been used traditionally [1,2,3,4] These techniques have a limited detection range for the gases as well as inferior sensitivity when compared to the use of mass spectrometry (MS). While more complex in operation, mass spectrometry allows the detection and quantification of a larger variety of gaseous compounds apart from oxygen and carbon dioxide, if one chooses to do so, within a single equipment This is in contrast to the mono-specificity of the non-MS sensors for the individual gases limited to just oxygen and carbon dioxide, the number of sensors will increase proportionally to the number of different gases of interest.

Methods

Results

Conclusion