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Effects of Elevated pCO 2 and Osmolality on Growth of CHO Cells and Production of Antibody‐Fusion Protein B1: A Case Study
Author(s) -
Zhu Marie M.,
Goyal Asti,
Rank Douglas L.,
Gupta Sunil K.,
Boom Thomas Vanden,
Lee Steven S.
Publication year - 2008
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp049815s
Subject(s) - osmole , chemistry , zoology , pco2 , plasma osmolality , biology , andrology , biochemistry , medicine , endocrinology , vasopressin
Partial pressure of CO 2 (pCO 2 ) and osmolality as high as 150 mmHg and 440 mOsm/kg, respectively, were observed in large‐scale CHO cell culture producing an antibody‐fusion protein, B1. pCO 2 and osmolality, when elevated to high levels in bioreactors, can adversely affect cell culture and recombinant protein production. To understand the sole impact of pCO 2 or osmolality on CHO cell growth, experiments were performed in bench‐scale bioreactors allowing one variable to change while controlling the other. Elevating pCO 2 from 50 to 150 mmHg under controlled osmolality (about 350 mOsm/kg) resulted in a 9% reduction in specific cell growth rate. In contrast, increasing osmolality resulted in a linear reduction in specific cell growth rate (0.008 h −1 /100 mOsm/kg) and led to a 60% decrease at 450 mOsm/kg as compared to the control at 316 mOsm/kg. This osmolality shift from 316 to 445 mOsm/kg resulted in an increase in specific production rates of lactate and ammonia by 43% and 48%, respectively. To elucidate the effect of high osmolality and/or pCO 2 on the production phase, experiments were conducted in bench‐scale bioreactors to more closely reflect the pCO 2 and osmolality levels observed at large scale. Increasing osmolality to 400–450 mOsm/kg did not result in an obvious change in viable cell density and product titer. However, a further increase in osmolality to 460–500 mOsm/kg led to a 5% reduction in viable cell density and a 8% decrease in cell viability as compared to the control. Final titer was not affected as a result of an apparent increase in specific production rate under this increased osmolality. Furthermore, the combined effects from high pCO 2 (140–160 mmHg) and osmolality (400–450 mOsm/kg) caused a 20% drop in viable cell density, a more prominent decrease as compared to elevated osmolality alone. Results obtained here illustrate the sole effect of high pCO 2 (or osmolality) on CHO cell growth and demonstrate a distinct impact of high osmolality and/or pCO 2 on production phase as compared to that on growth phase. These results are useful to understand the response of the CHO cells to elevated pCO 2 (and/or osmolality) at a different stage of cultivation in bioreactors and thus are valuable in guiding bioreactor optimization toward improving protein production.