Fetal Bovine Serum (FBS)

What is the difference between fetal bovine serum (FBS) and fetal calf serum (FCS)?

There is no difference. These are different names for the same product. Serum derived from blood of bovine fetuses is referred to as fetal bovine serum or fetal calf serum.

After I heat inactivated my serum, some precipitates are visible. Why?

Heat inactivated serum, including fetal bovine serum (FBS) may contain some turbidity, flocculent material, or crystalline precipitate. This is a normal occurrence with serum products and in no way indicates that the quality of the product has been compromised. Commonly, this material is composed of fibrin that has converted from the soluble precursor form, fibrinogen, in serum. Bio-Techne collects and processes all sera rapidly at cold temperatures to yield the highest quality serum with excellent growth properties. This rapid cold processing allows some soluble fibrinogen to remain in the serum after filtration which may convert to fibrin upon thawing.

Precipitates found in serum frequently also contain calcium complexes of inorganic serum components and proteins. Lipid serum components may also cause turbidity of the serum product. Incorrect thawing, frequent thaw-freeze cycles, heat inactivation, and extended storage at temperatures above freezing will result in a greater amount of precipitates. The presence of precipitates in serum does not alter the performance characteristics of the product when used as a growth supplement for cell culture. It is not recommended to filter the serum to remove these precipitates. Doing so may result in the loss of some serum nutrients and may clog the filter. Instead, if removal of the flocculence is desired, brief centrifugation of the serum in sterile tubes at 400 x g is recommended.

Can I still use my serum if it arrives partially thawed?

All Bio-Techne fetal bovine serum and other serum products are shipped frozen via overnight service and packaged in dry ice. Without a delay in shipping or at the receiving location, it should arrive frozen. In the event of delay and the serum becomes partially thawed, the serum can still be used. Thaw serum completely, mix gently, aliquot into single-use units if desired, and refreeze.

How should I thaw serum to ensure that the performance is not compromised?

Frozen serum should be thawed rapidly to avoid prolonged exposure of serum nutrients to higher salt concentrations during the thaw period. Thaw frozen serum at room temperature or in a 37 °C water bath. Periodically agitate the bottle during the thawing process to re-suspend the viscous solutes and to avoid the formation of salt, protein and lipid gradients that can lead to excessive precipitation. Promptly remove the serum from the water bath as soon as the serum is completely thawed. Thoroughly mix the thawed serum before it is added to a culture medium or is heat inactivated. Thawing of serum at temperatures above 37 °C is not recommended. This process may degrade heat labile nutrients, thus compromising the integrity and performance of the product, and can cause increased precipitate formation.

What procedure do you recommend for freezing serum?

Serum, including FBS, should be frozen as rapidly as possible to avoid prolonged exposure of serum nutrients to higher salt concentrations. Water is the first serum component to freeze, causing other serum components such as proteins and salts to accumulate at the bottom of the container at a higher concentration. Therefore, slow freezing will result in excessive formation of crystalline precipitates.

Does your fetal bovine serum contain any naturally occurring biotin?

Our FBS contains naturally derived biotin. We do not biotin-deplete nor measure the sera for biotin content.

Has this fetal bovine serum been tested for Bovine Spongiform Encephalopathy (BSE)?

We use a strict set of material sourcing and manufacturing policies to minimize the risk of BSE contamination. This includes only using material collected in U.S.D.A. approved slaughterhouses or in countries certified by the U.S.D.A. to be free of Foot and Mouth Disease (FMD), Bovine Spongiform Encephalopathy (BSE), and other exotic disease agents. We do not routinely perform BSE testing in our virus testing panel. For further information, please read our TSE/BSE policy at R&D Systems.

How should I determine which fetal bovine serum is most suitable for my cell culture system?

Bio-Techne requires all serum products to undergo rigorous testing to ensure consistent quality and proven performance even for the most sensitive cell culture systems. Because not all FBS needs are the same, Bio-Techne has developed a range of products that are tailored to specific cell culture requirements. Additional assays beyond the quality assurance and performance testing conducted on every FBS product, such as a hormone assay, are performed for some of our FBS products to address user-specific cell culture requirements.

How should serum be stored, and for how long?

Please refer to our Methods for Storage, Thawing, and Freezing of Serum Products protocol at R&D Systems.

Is serum light-sensitive?

Serum contains components that are affected by exposure to light. However, normal handling of serum under room lights should have little effect on the serum. The effect of light on the serum will depend upon the intensity of light, the wavelength of light and the duration of exposure. Therefore, high intensity lights and long-term storage under light should be avoided. Note that certain cell lines may be more sensitive to the effects of light on serum than other cell lines.

Why is serum heat inactivated?

Generally, the objective of heat inactivation is to destroy complement activity in the serum without affecting the growth-promoting characteristics of the product. Removal of complement activity from the serum is not required for most cell cultures, but may be necessary for cultures that are sensitive to the complement activity. Since heat inactivation of the serum may, to some extent, decrease the growth performance properties of the serum, this procedure should only be performed if actually required for optimal cell growth. If heat inactivation is required, the process should be carefully controlled to avoid increased denaturation of serum proteins and formation of crystalline precipitates, potentially resulting in excessive loss of growth performance. Initially, heat inactivation was also used to inactivate microbial contaminants such as mycoplasma. Heat inactivation for this reason is unnecessary, since Bio-Techne FBS is triple 0.1 µm filtered and all other Bio-Techne manufactured sera must test negative for mycoplasma, bacteria and fungi. Sometimes, heat inactivation is performed to disrupt susceptible viruses. In most protocols for this application, prolonged heat inactivation is required. This is not recommended, since valuable components of the serum are rendered ineffective by this treatment.

Why do some cell culture media contain sodium pyruvate?

Sodium pyruvate is added to many low glucose and high glucose DMEM formulations. Sodium pyruvate can be used by cells as a readily accessible carbon source for energy production and other critical metabolic pathways, bypassing the need to produce it biosynthetically from glucose or amino acids. Some cell lines require the addition of pyruvate to the culture media since they lack the ability to convert glucose or amino acids into pyruvate.

Why is there lot-to-lot variability in serum?

Fetal bovine serum and other serum products contain a complex mixture of biological components, a majority of which have not yet been fully defined. The composition of these serum components naturally varies from lot-to-lot. The best serum lot for you is the one that works for your cells in your specific application. Bio-Techne serum manufacturing has a 40 year history of experience, which provides some of the most consistent serum on the market. We can help you select the serum lot that is ideal for your application by offering a variety of programs such as lot matching, free samples for lot prequalification, extended lot reserves, and free on-site serum storage, geared towards minimizing the impact of serum variability for our customers.