Insert combination into host cell 5. Role of host, vector, and other conditions. Patenting animals and cells. Serious international issue, with ethical questions. Partly because of international issue, huge backlog of biotechnology patents.
Proteins have, even now, a delivery problem.
Similar to chemical process in that contaminants are present in protein or product being produced. Production is extraordinarily sensitive to tiny changes in host cells used for production. Even time of growth of cells can be an issue. Normally validation comes only at relatively late stage of production. Demonstrate that the same product is always produced.