Control of cell metabolism and multiplicity of steady state in the continuous culture of hybridoma cells

Under typical culture conditions, mammalian cells convert as much as 95% of the glucose consumed into lactic acid. The accumulation of lactate has adverse effects on cell growth and could limit the maximum cell concentration that can be achieved in the culture. Using a fed-batch culture to cultivate hybridoma, cells while maintaining a low-glucose environment, cells were adapted to a state where the production of lactate from glucose was drastically reduced.; Continuous culture was initiated with cells at very different metabolic states. Hybridoma cells cultivated in a batch culture with high glucose concentration retained a highly glycolytic type of metabolism characterized by high lactate production. Those cultivated in a fed-batch culture in which glucose concentration was controlled at a low level gradually switched to a low-lactate producing metabolic state and reached a higher viable cell concentration. When such cultures were switched to continuous operation under the same dilution rate and feed composition, they reached distinct steady states. The low-lactate producing culture initiated from fed-batch mode reached a higher concentration than the other initiated from a batch culture. The former had very little lactate accumulation, while the latter converted about 75% of glucose consumed to lactate. The results clearly demonstrated that with two different initial conditions, animal cell cultures can reach very different steady states in a continuous reactor under the same operating conditions. The important switching points of cell metabolism that explains the differences in metabolic activity, notably of lactate production, are also examined. The results may have a profound implication on the process strategy for animal cell cultivation. Current high-density continuous cell cultures rely on cell recycle and requires a high medium throughput to sustain the productivity. The requirement of the high medium throughput was largely due to the excessive metabolite accumulation. The success in manipulating cell metabolism and minimize lactate production in continuous culture may greatly reduce the need of a high perfusion rate and the cost of production.