Effect of pH Shifting on Human Albumin-EPO Production by Recombinant Chinese Hamster Ovary Cells

초록

Effects of environmental factors on cell growth and recombinant protein production have been widely investigated in Chinese hamster ovary (CHO) cell cultures. In addition, directed shifting of process parameters can be used as an optimization tool for providing higher cell and product yields. pH is a parameter known to influence cell growth, recombinant protein production, cell metabolism and protein glycosylation. In this work, we investigated the effect of pH on a recombinant CHO cell line expressing human albumin-erythropoietin (albumin- EPO), a highly glycosylated fusion protein. The culture pH was controlled at various levels (6.8, 7.0, and 7.2, respectively) by using 0.5 N NaOH. Maximum cell density reached up to 4.2 x 106cells/mL at day 4 by maintaining pH 7.2, which was 8% higher than that of control culture. The highest productivity was obtained at pH 6.8. However, lowering the culture pH led to cell aggregation. Based on these results, pH shift two-stage culture was performed. In the first half stage of cultivation, pH was controlled at 7.2 and the pH shifted at day 5 to 6.8 and 7.0, respectively. However, as reported in the previous studies, the culture pH at 37℃ did not influence albumin-EPO production. In conclusion, the pH shifting was found to be an efficient strategy for the increase of cell growth in CHO cell cultures. Therefore, it is expected that the simultaneous use of both pH and temperature shifting can improve the performance of CHO cells regarding cell growth, recombinant protein production and glycosylation.