Chemically modified cysteine in CHO fed-batch processes and impact on the specific productivity

High cysteine concentrations in cell culture media lead to oxidative stress and reduced bioprocess performance of recombinant CHO cells

“…In particular, free extracellular Cys, which is considered an antioxidant has been shown to function as a source of additional extracellular ROS formation by reacting with several other CDM ingredients such as Fe 2+ due to its highly reactive thiol groups. [ 7,8,33 ] In our study, the only difference between the individual LSCD and HSCD cultures was the concentration of Cys in the basal medium at the time point of inoculation. Consequently, we deduce that the additional extracellular Cys available directly caused oxidative stress beyond the threshold of antioxidant capabilities at LSCD, leading to redox imbalance presumably by drainage of GSH and/or overoxidation in the cytosol and ER.…”

“…Alternatively, it was demonstrated that by substituting Cys/(Cys)2 with S‐sulfocysteine the intracellular GSH pool can be improved. [ 8 ] Further fine‐tuning of trace elements in media formulations such as, for example, iron was shown to reduce extracellular ROS formation. [ 10 ] It is important to mention that the measured RNA levels do not necessarily correlate with the functional protein expression.…”

“…Lately, the composition of CDM used for biomanufacturing has been shown to cause oxidative stress thus impacting cell culture performance and product quality. [5][6][7][8][9] In particular, the semi-essential amino acids L-cysteine (Cys)/cystine were shown to function as a source of reactive oxygen species (ROS) formation by reacting with several other CDM ingredients such as iron (Fe 2+ ) due to their highly reactive thiol groups. [8,10,11] In cell culture and even after media preparation, Cys is rapidly oxidized in presence of air or metal ions into L-cystine ((Cys)2) due to its high reactivity.…”