Fed-batch culture is the prevailing method to cultivate cells for production of recombinant proteins. Mining a large number of bio-manufacturing process data revealed a strong correlation between metabolic shift to lactate consumption and higher productivity. This transition to lactate consumption is accompanied by a low glycolysis flux and occurs under slow growth conditions. Despite the seemingly identical culture condition in different runs, the same cell line may behave differently. Understanding this phenomenon may help devise more robust strategies to control lactate metabolism and achieve desirable culture performance.<br/>In this study, we examine another  type of “unpredictable” behavior of metabolic shift. Using a mechanistic kinetic model of energy metabolism of the glycolysis, TCA cycle and pentose phosphate pathways, we examined the multiplicity of steady states of glycolysis flux and the mechanisms of metabolic shift to lactate consumption. We demonstrate that such metabolic state shift can be explained by the multiple steady state behavior of the energy metabolism. The data compiled from different manufacturing runs supports the model prediction qualitatively. A closer examination of data also revealed that many cultures had a transition from a high glycolytic flux (also marked by high lactate production) to a low flux state with little lactate production. After a period of low glycolytic flux, some cultures resumed lactate production while others switched to lactate consumption. In other words, some cultures had a metabolic “shift-up” to a high flux state while other remained in a low flux state and began to consume lactate. To investigate the mechanisms of this behavior, we examine the carbon flux distribution among metabolic pathways under different flux states. We also inspect the concentrations of intracellular metabolites, especially those involved in the regulation of metabolic homeostasis of the cells. Insights from this study will help improve our understanding of lactate metabolism, and facilitate the development of strategies to increase the robustness of cell culture process through a better metabolic control.

On the shift-up to high lactate production in fed-batch culture of mammalian cells

253rd National Meeting (2017)

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