• Fetal Bovine Serum (FBS) originates from the blood drawn from a bovine fetus in a closed system of collection at a slaughterhouse. FBS has a high content of embryonic growth promoting factors and is the most widely used serum supplement for in-vitro cultures.

    • Fetal Bovine Serum (FBS) and other bovine serum is a by-product of the meat industry. FBS comes from blood taken at the time of slaughter from a bovine fetus when female cows that are slaughtered for the human consumption of meat are subsequently found to be pregnant.

    • Ideally, removing the bottle of serum from frozen storage and allowing to thaw overnight at room temperature (or 12 hours) is the best way. Homogenize the serum once thawed without making the serum foam. If you are not able to plan accordingly, you can also thaw the bottle of serum in a shaking/heated water bath set to 37⁰C until completely thawed.

      • Remove the desired bottle of serum from frozen storage.
      • Begin by thawing the bottle of serum either at room temperature or use a heated/shaking water bath to thaw at 36⁰C until competed thawed. Be sure to set the shaking controls to slow in order to avoid possible submersion of bottles in water. If shaking water bath is not available, occasionally, swirl the bottle of serum gently to avoid precipitant from forming during the thawing and Heat Inactivation process.
      • Once completely thawed, turn on the heated water bath (if not already on) and set to 56⁰C. Place both the bottle of serum and the control bottle with thermometer in the water bath.
      • Closely monitor the control bottle’s temperature and once the thermometer reads 56⁰C, use a 30 minute timer and initiate heat inactivation procedure. During those 30 minutes, check the temperature regularly to ensure a stable temperature reading 56⁰C (+/-) 3⁰C.
      • Once 30 minutes has elapsed, remove bottle of serum and control bottle, set aside at room temperature for 30 minutes – 1 hour (once the bottles have cooled), proceed to freeze the serum at ≤ -20⁰C.
      • Drain water bath and clean accordingly in reference with Good Lab Practices.

      The use of a heated/shaking water bath is highly recommended to ensure serum is properly mixed and is crucial to maintain serum quality. If not mixed properly, precipitants of proteins, lipids and salts will form. In the event a heated/shaking water bath is not readily available, be sure to gently swirl / mix the bottles of serum every 5-10 minutes to avoid inconsistencies of product quality. Heating the serum for elongated periods of time can destroy growth promoters and can enable deposits to form.

    • Heat Inactivation degrades complement proteins that could interfere with specific assays. For most cell culture settings and applications, heat inactivation is not recommended. Effects of Heat Inactivation include a reduction in growth factors, increase of deposits which are commonly mistaken for microbial contamination and reduce performance of the serum.


    • USDA-Approved indicates that the serum’s origin ( or source ) is from a USDA-Approved country. The serum is produced from blood collected in countries that have been approved by the United States Department of Agriculture (USDA) and deemed fit to export ruminant serum products to the United States of America. Eligible countries that export fetal bovine serum into the United States of America include: Australia, Canada, Chile, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, New Zealand and Panama.

    • On occasion, turbidity and flocculent deposits may be present after prolonged freezing / refrigeration of serum. These deposits have no affect on the biological performance of the serum and are cosmetic.

      Multiple freeze-thaw cycles increase the chance for precipitates being present in the serum. Fibrinogen is the clot-forming protein (Fibrin) and appear as white flakes. Fibrin could present itself after thawing or heat inactivating the serum. Fibrin does not alter the performance of the serum and poses no threat to cultures. Commonly, Fibrin is mistaken for mycoplasmas contaminations in lab settings and is not harmful.

    • To the best of our knowledge, the serum’s origin has no influence on cell growth. Commonly, one lot of fetal bovine serum (FBS) may exceed the control of a specific cell line but not for another. Serum quality is specific for each cell line and can vary. These variation may include (but not limited) to: Geographical location, the time of year the blood was collected and dietary factors etc. Peak Serum strongly encourages our customers to test prior to purchasing to ensure total satisfaction.

    • Yes, bovine serum is categorized according to the age of the animal from which the blood was collected.

      • “Fetal Bovine Serum” originates from fetuses
      • “Newborn Calf Serum” originates from calves ≤ 3 weeks of age
      • “Calf Serum” originates from calves between ≥ 3 weeks – 12 months of age
      • “Adult Bovine Serum” originates from cattle ≥ 12 months of age
    • When serum receives a standard dosage of gamma irradiation, no initial loss of performance is observed.

      Gamma Irradiation kills viruses, it also effects proteins and reduces the hemoglobin level in the serum which can modify the physical appearance of the serum.

      However, gamma irradiation decreases the serum metabolites and could slightly affect grow promotion, cloning and plating efficiency with some cell lines. These possible observed results can vary depending on specific applications.

    • Storage temperatures of -10⁰C to -40⁰C are recommended for serum storage. Temperatures below -40⁰C may allow the bottles to become delicate and increase the risk for breakage. It is important to avoid direct exposure to light.

    • On occasion, gamma irradiation is needed to eliminate all potential virus risks in serum.

    • Endotoxin is a complexed lipopolysaccharide (LPS), a toxic substance found in the outer cell membrane of most gram-negative bacteria. The bacteria releases endotoxin into the culture environment while growing and upon cell death.

      Studies have shown that endotoxin levels may possibly affect the growth or performance of some cultures in specific applications but does not affect all cells equally.

      Industry standard for endotoxin in fetal bovine serum (FBS) is ≤ 10 EU/ml with the highest grade reporting at ≤ 1 EU/ml. Peak Serum provides low-endotoxin FBS but generally this is not necessary for many cell lines and applications. We are happy to offer a wide range of cost effective FBS products to help personalize your serum needs.

    • Hemoglobin is a protein in red blood cells found in finished fetal bovine serum (FBS). Cell fractionation can occur during transportation/handling and processing of raw fetal blood. This can alter the appearance or color of the finished FBS. Generally, normal levels of total hemoglobin in FBS range from 10 – 30 mg/dL and higher concentrations have virtually no effect on cell culture or the quality of the FBS.

    • Mycoplasmas are very small bacteria lacking cell walls that belong to various genera within the class Mollicutes.  They are considered to be the smallest-free living organisms and most commonly discovered in research laboratory settings where cell culture is present.

      Peak Serum’s filtration scheme utilizes triple 0.1 micron membrane sterile filters that effectively remove mycoplasma from our serum.  Every lot endures stringent testing for mycoplasmas after final filtration and prior to final release to ensure your research is protected.  Our serum is tested for mycoplasmas by 9CFR 113.28 for 28 days.

    • Serum that is incubated for extended periods of time (heated water bath > 37⁰C) may become cloudy and deposits may appear. This is caused by calcium and phosphorous and to the best of our knowledge, does not affect or change the performance of the serum in culture.

    • The following is a detailed outline on how to best adapt cell lines to new lots of Fetal Bovine Serum. It is the responsibility of the individual to determine the best method per each unique situation. Minor adjustments to stated protocol are always cell dependent. Click here for the full protocol.