Animal-Origin-Free ITS-X 100X Supplement

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• Recombinant Human Albumin in Cell CultureRecombinant human serum albumin (rHSA) is a 585-amino-acid, 66.5 kDa non-glycosylated protein produced in yeast such as *Pichia pastoris* or in transgenic rice rather than purified from human plasma, and it is used as an animal-origin-free supplement in serum-free and chemically defined culture media. In culture it works as a carrier for fatty acids, lipids, hormones and trace elements, as an antioxidant through its free cysteine-34 thiol, as a scavenger that sequesters toxic metals and excess free fatty acids, and as a shear-protective surface-active protein in stirred and sparged culture. Typical working concentrations are 0.1-10 g/L, most often 0.5-5 g/L, and it is commonly supplied as a 200 mg/mL (20%) solution. Its performance depends heavily on what is bound to it, so fatty-acid-loaded and fatty-acid-free preparations behave quite differently.
• Recombinant Human Insulin in Cell Culture: Working Concentrations and ITSRecombinant human insulin is a 51-amino-acid, 5.8 kDa two-chain protein used as a core supplement in serum-free and chemically defined culture media, where it drives glucose and amino acid uptake, protein and lipid synthesis, and cell survival. It is produced in *E. coli* or yeast rather than extracted from animal pancreas, making it animal-origin-free, and is usually supplied as a zinc-stabilised dry powder. The typical working concentration is 5-10 ug/mL, the level delivered by a standard 1X ITS supplement, which is roughly a thousandfold above physiological insulin levels -- at that concentration insulin acts substantially through the IGF-1 receptor as well as its own. Because insulin is poorly soluble near neutral pH, powder must be dissolved in dilute hydrochloric or acetic acid before dilution into medium.