Abstract
In mammalian cell culture, especially in pharmaceutical manufacturing and research, biomass and metabolic monitoring are mandatory for various cell culture process steps to develop and, finally, control bioprocesses. As a common measure for biomass, the viable cell density (VCD) or the viable cell volume (VCV) is widely used. This study highlights, for the first time, the advantages of using VCV instead of VCD as a biomass depiction in combination with an oxygen-uptake- rate (OUR)-based soft sensor for real-time biomass estimation and process control in single-use bioreactor (SUBs) continuous processes with Chinese hamster ovary (CHO) cell lines. We investigated a series of 14 technically similar continuous SUB processes, where the same process conditions but different expressing CHO cell lines were used, with respect to biomass growth and oxygen demand to calibrate our model. In addition, we analyzed the key metabolism of the CHO cells in SUB perfusion processes by exometabolomic approaches, highlighting the importance of cell-specific substrate and metabolite consumption and production rate qS analysis to identify distinct metabolic phases. Cell-specific rates for classical mammalian cell culture key substrates and metabolites in CHO perfusion processes showed a good correlation to qOUR, yet, unexpectedly, not for qGluc. Here, we present the soft-sensoring methodology we developed for qPyr to allow for the real-time approximation of cellular metabolism and usage for subsequent, in-depth process monitoring, characterization and optimization.
Highlights
Chinese hamster ovary cells (CHO) represent the backbone of commercial and research expression hosts used for the manufacture of monoclonal antibodies for therapeutic purposes
All CHO lines were derived from the same native CHO host cell line, we detected, as shown before by others, significant, process time-dependent differences in cell growth characteristics, such as viable cell density formation and timing for cell doubling, as well as in volume per cell among all tested clones (Figure 3A,C,E)
In our study, we were aiming for a biomass soft-sensor model that can handle the metabolic diversity and its effects on process properties that are caused by the varying clonal behavior of not yet in-depth, characterized CHO cell lines
Summary
Chinese hamster ovary cells (CHO) represent the backbone of commercial and research expression hosts used for the manufacture of monoclonal antibodies (mAB) for therapeutic purposes. Single-use bioreactor (SUB) systems have gained tremendous interest in the biopharmaceutical industry as these bioreactors and their peripheral solutions can remarkably elevate the efficiency and, the flexibility of modern manufacturing processes [3]. Monitoring sensors that can be applied to SUB systems and deliver high-grade, real-time information is a significant need, especially for one of the most valuable indicators, the biomass concentration [7,8]. Even if common sensor systems, e.g., hard-type sensors that have been adjusted to match single-use bioreactor requirements, are available [9], there is still a challenge to measure the biomass concentration online [10]. Online biomass estimation via off-gas measurement generally relies on the oxygen uptake rate (OUR) as this variable is one of the best indicators for cell physiological activity and correlates very well with metabolic turnover rates and the concentration of viable biomass
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