(665c) Bioprocess Optimization for Production of Recombinant Proteins in Chinese Hamster Ovary Cells in Consideration of Metabolic Shifts By Shear Stress

Biopharmaceuticals such as monoclonal antibody drugs have attracted considerable interest in recent years for currently untreatable diseases. A series of large production plants have been built in different parts of the world. Chinese hamster ovary (CHO) cells are widely used as a host cell line and cultured in fed-batch cultivation in a large stirred bioreactor for commercial production of biopharmaceuticals. When a bioreactor is designed for commercial-scale production, it is indispensable to evaluate the impact of shear stress on cell growth and cell viability due to their mechanical fragility. In this study we focused on the impacts of shear stress on cellular metabolism to optimize fed-batch cultivation for production of tissue plasminogen activator (tPA) in CHO cells.

We went through the two steps to optimize a fed-batch cultivation process. The first step is the quantitative evaluation of the effects of shear stress. In the case of a stirred bioreactor, a quantitative evaluation is difficult to be performed due to the distribution of shear stress in a tank. Therefore we introduced a flow chamber which can impart a steady laminar shear stress on the cells for the evaluation of the effects of shear stress and found that metabolism shift occur with increased shear stress. We determined the appropriate range of shear stress for the production from the results. The second step is the optimization of an impeller configuration and feed medium in consideration of the metabolism shift. We designed 3L bioreactors which sustain appropriate shear stress in a tank using computational fluid dynamics (CFD) and feed medium in consideration of metabolism shift. CHO cells producing tPA protein were cultured with our optimized bioprocess. As a result, the production of tPA increased by 1.5 times compared to the conventional fed-batch process.

We found that metabolism shift occur by increasing shear stress and the optimization of a bioprocess taken into account the metabolism shift contributes to increasing productivity.