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Serum is a byproduct of meat production and is the liquid portion that remains after blood is coagulated. Serum is added to what’s called basal media to promote growth and maintenance of eukaryotic cells, including mammalian and insect cell lines. This common cell culture supplement provides nutrients to cells. Among these are hormones, growth factors, and minerals.

Serum is typically added to basal media to a final concentration of 5% of 10%. It’s used in many applications in research and industry, particularly for vaccines and viral vectors. Care must be taken to ensure that serum doesn’t contain viruses, as these will contaminate the cell culture.

  • Origin is where the raw material comes from. This is important because sera can contain viruses, which vary by region. To support security of supply, we recommend qualifying sera from other origins.
  • Source is the type of animal that the raw material comes from – typically cows. There are several categories of bovine serum. These include fetal bovine serum (FBS), which is from fetuses, and bovine calf serum, which is from young animals. Horses are the source for equine serum.
  • Processing is how the raw material is treated to prepare the final cell culture serum product. Typically, the raw material is treated to remove microbes or natural serum constituents that can disrupt analyses or assays. Filtration is one of the standard treatments for sera, with variation in the pore size and number of filtration steps used. Higher quality sera are processed with one or more rounds of 100 nm (0.1 µm) filtration or even with 40 nm filtration. After filtration serum can be treated further with, for example, gamma irradiation.
  • Testing is how the product is analyzed. A wide range of testing is possible, for specific viruses, among other things. Endotoxin level is a common test. Higher quality sera have extremely low endotoxin levels.

Engineered and non-fetal cell culture serum products are designed to be cost-efficient, high-performing replacements for FBS. These products contain several naturally occurring factors that promote growth.

Variability in serum components is natural and results from a variety of factors, such as age and geographical origin. To reduce this variability, each lot of Cytiva’s HyClone™ serum is pooled after filtration and before dispensing to ensure uniformity and consistency between bottles. This true pool processing increases the consistency and quality of our serum products.

Learn more about Cytiva sera.


  • Do keep your bottle of serum frozen at approximately ≤ -10°C until just before use.
  • Do follow thawing protocols.
  • Do refreeze serum after use.
  • Do aliquot out samples to minimize the number of thaw/freeze cycles on serum products.
  • Do always handle serum under aseptic conditions, such as in a biosafety cabinet (BSC).


  • Don’t handle cell culture serum in nonsterile conditions, such as on a benchtop.
  • Don’t immerse serum bottles in water baths anywhere close to the cap. Otherwise, you risk contaminating your serum with microbes from the water.
  • Don’t thaw above 37°C, as this can inactivate some serum components.
  • Don’t keep in a frost-free freezer, as temperature cycling could lead to cracked bottles and precipitation.