Conference Dates

May 6-11, 2018


Normally the growth profile of a CHO cell fed-batch process can be divided into a growth phase followed by a stationary (non-growth) phase and a cell death phase. In this study, using a commercially available media system in a 10 liter fed-batch reactor, the growth phase is followed by a phase where cell division stops but cell growth continues in the form of an increase in cell size (Figure 1). During the cell size increase (SI) phase, the average volume and dry weight per cell increase linearly with time up to nearly threefold. Cell cycle and transcriptome analysis show that the cell size increase is related to an arrest of cells in the G1 and G2 phase of the cell cycle in combination with a continued biomass formation. The SI phase is characterized by accumulation of fatty acids and formation of lipid droplets in the cells. Furthermore, the mAb specific productivity per cell increases linearly with the cell volume, while the specific essential amino acids consumption rates per cell remain fairly constant and comparable to that in the NI phase. As a consequence the yield of product on nutrients increases in the SI phase. Metabolic flux balancing shows that also the yield of product on oxygen consumed and CO2 produced is increased in the SI phase, which means lower gas-flow rates can be used to reach the same volumetric productivity. In summary, cell size is an important parameter to consider in CHO cell processes. A better mechanistic understanding on how the cell size is influenced by process conditions can be used to further optimize these processes.

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