主权项 |
1. A method of culturing Chinese Hamster Ovary (CHO) cells expressing a recombinant protein, comprising growing the CHO cells in a defined serum-free culture medium during a growth phase and maintaining the CHO cells in the cell culture medium during a production phase by supplementing the cell culture with a concentrated defined serum-free feed medium that does not contain tyrosine, cysteine or cystine, and further supplementing the cell culture with an independent tyrosine and cystine feed, wherein viability was prolonged, specific productivity and titer was not diminished by the independent tyrosine and cystine feed. |