(133b) Metabolic Flux Analysis of CHO Cells In Semi Fed-Batch Culture

Mammalian cell culture is of key importance for biopharmaceutical companies for the production of recombinant proteins, monoclonal antibodies and vaccines. In recent approvals in US and EU, the majority of biotherapeutics were produced by mammalian cell lines and of those a large fraction by Chinese Hamster Ovary (CHO) cells. Metabolism of CHO cells is characterized by high rates of glycolysis and glutaminolysis. As a result, large amounts of lactate and ammonium accumulate during the culture from the conversion of glucose to lactate and the decomposition and metabolism of glutamine. The cellular by-products inhibit cell growth and protein production and can deteriorate the glycosylation quality of the proteins. Relatively little is known about the intracellular metabolism of CHO cells in cell culture. In this work, the intracellular metabolism of CHO cells was studied in detail in a typical semi fed-batch culture. Intracellular metabolism was characterized by extracellular uptake and excretion rates of metabolites combined with a metabolic network model for CHO cell metabolism. To obtain additional information ¹³C-tracers were applied and ¹³C-labeling was measured using mass spectrometry. The flux results revealed significant rewiring of intracellular metabolic fluxes in the transition from growth to non-growth including changes in energy metabolism and redox metabolism. The results presented here provide a solid foundation for future studies of CHO cell metabolism for applications such as cell line development and medium optimization for high-titer production of recombinant proteins.