Low-Endotoxin Bovine Serum Albumin Powder

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• Endotoxin Testing in Cell CultureEndotoxin testing measures bacterial lipopolysaccharide (LPS) in laboratory water, media, sera and reagents, reported in endotoxin units per millilitre (EU/mL), where 1 EU corresponds to roughly 0.1–0.2 ng of reference-standard E. coli endotoxin. The compendial methods are the LAL (limulus amebocyte lysate) assay in its gel-clot, turbidimetric and chromogenic forms under USP <85>, and the animal-free recombinant Factor C (rFC) assay under USP <86>; kinetic formats quantify down to about 0.001–0.005 EU/mL. Practical cell-culture limits are 0.25 EU/mL for water, ≤1 EU/mL for most cell-culture-grade reagents, and ≤10 EU/mL as the general industry standard for fetal bovine serum, with low-endotoxin grades at ≤1 EU/mL and ultra-low grades below 0.1 EU/mL. Endotoxin survives autoclaving and passes 0.2 µm filters, so it must be excluded at source rather than removed later.
• 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.