Used in cell culture media as a key amino acid source, especially in biopharmaceutical production where it supports the growth of mammalian cells. Commonly added to formulations for monoclonal antibody and recombinant protein manufacturing. Also serves as a nutrient in parenteral nutrition solutions for patients unable to take food orally. Employed in some enzyme assays and biochemical research to study metabolic pathways involving serine. Its hydrochloride form improves solubility and stability in acidic conditions.