Probing lactate metabolism variations in large-scale bioreactors
May 6-11, 2018
Lactate metabolism variations are frequently encountered in mammalian cell culture processes, especially during process scale-up. In this work, we took a multipronged approach to investigate the impact of pH, pCO2, osmolality, base addition, and mixing conditions on the observed lactate variations in a Chinese Hamster Ovary (CHO) fed-batch process at 2,000 L scale. Two cultivating methods, CO2-controlled and pH-controlled, were used to decouple the individual and synergistic effects from those factors. The individual effects from pH, pCO2, and osmolality on lactate consumption/reproduction in the stationary phase were insignificant in the ranges studied though the initial lactate production rates varied. In contrast, lactate metabolism was found to be impacted by an interaction between mixing conditions and CO2 accumulation. High CO2 accumulation and poor mixing led to lactate reproduction, whereas either low CO2 or improved mixing were sufficient to result in lactate consumption. Base addition was not required for pH control in the low CO2 conditions, and therefore lactate reproduction was correlated with base addition under poor mixing conditions and high CO2. Under good mixing conditions, CO2-triggered base addition did not pose significant impact on lactate reproduction. It is reasonable to postulate that increased mixing times promoted lactate production during base addition. As lactate reproduction results in more base addition to maintain pH, a cycle could be formed between lactate production and base addition. As a remediation, we showed that lactate reproduction could be eliminated by improving CO2 removal at 2,000 L scale.
Sen Xu, Rubin Jiang, Roland Mueller, Nadja Hoesli, Thomas Kretz, Hao Chen, and John Bowers, "Probing lactate metabolism variations in large-scale bioreactors" in "Cell Culture Engineering XVI", A. Robinson, PhD, Tulane University R. Venkat, PhD, MedImmune E. Schaefer, ScD, J&J Janssen Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/ccexvi/224