Some aspects of the present disclosure provide methods, compositions and kits for identifying one or more reagents, such as a culture medium, that are effective for recombinant protein production.

There is a need for alternative methods for recombinant expression of functional insulin and/or insulin analogs having its native conformation. The present disclosure provide methods for producing functional, recombinant protein having its native conformation in mammalian host cell cultures wherein the recombinant protein is an insulin analog and/or a derivative thereof.