Chinese hamster ovary (CHO) cells account for a significant portion of recombinant protein production throughout the biopharmaceutical industry. Because of this, growth efficiency is extremely important to cut down on production costs as well as to obtain an optimal protein yield. Currently, pH in CHO cells is controlled through a combination of CO2 sparging coupled with a bicarbonate buffered medium. Bicarbonate buffered medium relies on the equilibrium between sparged CO2 gas in the bioreactor along with dissolved CO2 in the medium. However, these bicarbonate and dissolved CO2 levels are well above physiological conditions and have been shown to negatively impact growth. Also, metabolically active cells produce additional CO2. A culture medium buffered without sodium bicarbonate would eliminate CO2 sparging and remove the co-dependence of dissolved oxygen (DO) and pH within the system. Bicarbonate-free medium also allows for more sensitive CO2 off-gas measurements, which would allow for improved real-time monitoring of the metabolic activity of the cells. In this work, parallel growth experiments were performed where CHO DP-12 cells were cultured in either medium buffered with bicarbonate or a MOPS- and HEPES-buffered medium. Prior to the computer-controlled bioreactor studies, shake flask studies were performed to compare growth in each medium. Similarly, growth studies were performed in 1-liter bioreactor where the CO2 off-gas measurements were assessed for sensitivity to glucose pulses as a means to quantify the metabolic state of the cells. These growth comparisons will be presented highlighting the effectiveness of each medium for high-density cell cultures.

Evaluation of bicarbonate free medium for improved mammalian cell growth and monitoring in controlled bioreactors

249th National Meeting (2015)

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