This is an interesting question. We have tried both methods. The most common media used for bioproduction is chemically defined media. In many cased there are internal proprietary formulations. We tested Cell Ess in a chemically defined system as part of an optimization strategy to see if we could improve performance of the system. We found a benefit if we added Cell Ess as either an initial supplement or as feed.
In serum containing systems we adopted the system to serum free and then were able to see similar performance as was in the serum containing media.