✍ Scribed by Shinya Takuma; Chikashi Hirashima; James M. Piret
No coin nor oath required. For personal study only.
The culture levels of glucose and CO~2~ have been reported to independently have important influences on mammalian cell processes. In this work the combined effects of glucose limitation and CO~2~ partial pressure (__p__CO~2~) on monoclonal antibody (IgG) producing Chinese Hamster Ovary cells were investigated in a perfusion reactor operated with controlled cell specific medium feed rate, pH and osmolality. Under high glucose conditions (14.3 ± 0.8 mM), the apparent growth rate decreased (from 0.021 to 0.009 h^−1^) as the __p__CO~2~ increased to ∼220 mmHg, while the cell specific IgG productivity was almost unchanged. The lactate yield from glucose was not affected by __p__CO~2~ up to ∼220 mmHg and glucose was mainly converted to lactate. A feed medium modification from high (33 mM) to low (6 mM) glucose resulted in <0.1 mM glucose in the culture. As a result of apparently shifting metabolism towards the conversion of pyruvate to CO~2~, both the ratio of lactate to glucose and the alanine production rate were lowered (1.51–1.14 and 17.7–0.56 nmol/10^6^ cells h, respectively). Interestingly, when the __p__CO~2~ was increased to ∼140 mmHg, limiting glucose resulted in 1.7‐fold higher growth rates, compared to high glucose conditions. However, at ∼220 mmHg __p__CO~2~ this beneficial effect of glucose limitation on these CHO cells was lost as the growth rate dropped dramatically to 0.008 h^−1^ and the IgG productivity was lowered by 15% (P < 0.01) relative to the high glucose condition. The IgG galactosylation increased under glucose‐ limited compared to high‐glucose conditions Biotechnol. Bioeng. 2007;97:1479–1488. © 2007 Wiley Periodicals, Inc.
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