An unstructured model of metabolic and temperature dependent cell cycle arrest in hybridoma batch and fed-batch cultures

Abstract

Cell productivity in fed-batch processes can be increased by cell cycle arrest through mild hypothermia. However, hypothermia can simultaneously reduce cell growth, which is regulated by the cell cycle. Consequently, the time point for the temperature shift is important and requires optimization while considering the cell cycle. An unstructured cell cycle model which includes the distribution of proliferating (G1, S, G2/M) and arrested cells (G0) has been proposed in order to predict the time point of temperature shift in fed-batch cultures. A model development and analysis framework that enables the evaluation of the required model parameters is described. The parameters are estimated from (fed)-batch cultivations, carried out at 37°C and at 33°C in order to characterize temperature dependency. The batch cultures are also used to evaluate substrate depletion and fed-batch cultures are used to study the impact of metabolite accumulation on the cell cycle. The reliability of the proposed framework for parameter estimation is validated using a mAb-producing hybridoma cell culture and the model predicts hypothermic transitions within the cell population at different shift time points. In conclusion, this framework can be used to optimize the time point of the temperature shift, which is commonly adjusted in industrial fed-batch processes in order to obtain a good balance between temperature induced growth limitation and cell cycle specific enhanced productivity.