You need to be aware that different nutrients are used at different rates and what is overly utilized is cell specific. With CHO cells glutamic acid, aspartic acid and cystene are self limiting and need to be part of a perfusion medium. Glutamine or glutamine dipeptide needs to be added at about 0.5 mM in the medium and with CHO cells the glucose concentration should be monitored and adjusted daily to 1.0 G/L.