Biological additives such as yeast extracts and peptones are commonly used in growth-media formulations for biopharmaceutical manufacturing. In spite of drivers encouraging companies to reduce variability in mammalian cell culture processes by using chemically defined media, many microbial and mammalian processes continue to use biological additives in their growth-medium formulations and/or feeds. According to Sheffield Bioscience (Kerry, Inc.), at least six of the top 10 licensed mammalian-cell– derived biotherapeutic products are manufactured using biological additives (1). During process development, it…