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If by system, you mean cell culture vessels, this is highly dependent on the type of cell lines used and the protein being expressed. Currently these include a combination of glass, stainless steel, CellSTACK, and WAVE systems.
If you mean the source, this also very dependent on the protein. In most cases we use an E.coli expression system, the most widely used cell type for animal-free processes. However, in some cases proteins require folding or glycosylation that is not conducive to the use of E. coli. Here we typically use an Sf9 insect cell line that has been certified animal-free. We do also have some examples where we use CHO or NSO lines to ensure we have the best combination of consistency and activity. These are still made using GMP guidelines for Cell Therapy manufacturing, but are not considered animal-free.