Abstract: The aim of this study is to understand the effects of pCO2 and osmolality on the monoclonal antibody（mAb）production during the maintenance phase of Chinese hamster ovary（CHO）cell cultures. Cell maintenance，metabolism，antibody quantity and quality at different pCO2 and osmolality levels were investigated during cell maintenance. It was found that the raise of pCO2 and osmolality brought negative impacts on final antibody production. The increase of osmolality damaged the cell maintenance，while the increase of pCO2 down-regulated the productivity of CHO cells. Through comparing the extracellular and intracellular metabolites，the increase of pCO2 and osmolality resulted in the decrease of carbon source utilization. Besides，on the antibody quality，the increase of osmolality decreased the glycosylation but raised the ratio of neutral charge. Moreover，the increase of pCO2 mainly enhanced the charge heterogeneity but there were no changes on the sugar type distribution of the products. Conclusively，the increase of pCO2 and osmolality during the phase of antibody expression had unfavorable effects on the cell maintenance，both material and energy metabolism，and the expression of product antibody；thus the accumulation of CO2 and osmolality elevation should be avoided as much as possible in order to ensure the normal proceeding of large-scale culture.

Key words: pCO2, osmolality, CHO cells, monoclonal antibody, metabolism