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Common Questions & Answers

1.) Are Serum Source International's products tested for potential viruses?

Yes, our Fetal Bovine Serum complies with title 9 of the FDA’s Code of Federal Regulations, 9CFR 113.53.  A complete 9CFR Virus Assay is performed.  Specific viruses tested are:

Bovine Viral Diarrhea Virus (BVD), Bovine Parvovirus (BPV), Bovine Adenovirus 3 (BAV-3), Bovine Adenovirus 5 (BAV-5), Bovine Respiratory Syncytial Virus (BRSV), Reo Virus, Rabies Virus, Bluetongue Virus (BTV), Infectious Bovine Rhinotracheitis Virus (IBRV) and Parainfluenza Type 3 Virus (PI-3).

Fetal Bovine Serum lots are also tested for cytopathic effects, commonly known as CPE.  Cytopathic effects are present when a virus causes a noticeable alteration in the physical appearance of the cells that are infected.

Furthermore, A hemadsorption assay (HA) is performed on all Fetal Bovine Serum lots to identify any hemadsorbing agents.

Please view our sample Certificate of Analysis for more details.

Note: Other types of animal serum are virus screened according to Industry Standards.

2.) What is Serum Source International's endotoxin level specification for premium Fetal Bovine Serum?

Our endotoxin level specification meets the industry standard of < 10.0 EU/ml.  Typically, our lots are < 1.0 EU/ml.  Specific endotoxin ranges can be requested for research applications that require very low endotoxin levels, such as < 0.05 EU/ml. 

Additional testing result specifications can be viewed on our detailed Certificate of Analysis, which is included with every Fetal Bovine Serum lot. 

3.) My endotoxin level result is recorded in the measurement ng/ml. How do I convert this measurement to EU/mL?

Please use the following example to convert your endotoxin level:

0.1 EU/mL = 0.01 ng/mL
1 EU/mL = 0.1 ng/mL
10 EU/mL = 1.0 ng/mL

4.) Does Serum Source International Fetal Bovine Serum contain tetracycline?

Very low levels of tetracycline may be detected in Fetal Bovine Serum.  For specific expression research studies using Tet-on/Tet-off systems, Serum Source International offers Tetracycline Negative Fetal Bovine Serum.  Tetracycline Negative Fetal Bovine Serum is ideal for gene expression systems and transfection applications.  The presence of tetracycline is screened using the ELISA method. 

5.) Does Serum Source International recommend heat inactivating my Fetal Bovine Serum?

We advise customers to better understand the need to heat inactivate and consider whether or not it is actually necessary for your application.  In early years of cell culture, before the introduction of Fetal Bovine Serum, Adult Bovine Serum was widely used which contained components such as antibiotics, unwanted complement factors and higher levels of animal viruses.  Heat inactivation was thought to be required to destroy heat-labile complement proteins.   

Also, there has been concern that certain viruses, including mycoplasma, may still be present after the filtration of serum.  Today, raw serum is first pre-qualified prior to processing.  Fetal Bovine Serum is filtered through three sequential 0.1 µm pore sized sterile filters and filled under class 1000 (or better) conditions into sterile PETG bottles, almost eliminating the necessity for heat inactivation in such cases concerned for contamination.  Our stringent quality control test parameters require that our Fetal Bovine Serum lots are tested for mycoplasma prior to the release for sale.  A complete 9CFR Virus Panel is also completed and reported on every Certificate of Analysis for each batch of Fetal Bovine Serum. 

In most cases, we find that heat inactivation is not necessary, unless required in laboratory protocol and/or for your particular research goal.  

6.) How do I heat inactivate my serum?

We recommend a careful and controlled approach when heat inactivating your serum to avoid damaging valuable growth factors and reducing the risk of possible undesirable precipitants that may form with repeated thaw/freeze cycles. 

Click here for our detailed printable PDF Heat Inactivation Procedure Instructions.

7.) What are precipitates?

Serum which has been thawed, frozen or heat inactivated may contain some fibrinogen, turbidity, flocculent material or crystalline precipitates. Small amounts of these are not uncommon, even in serum that has been properly handled, stored and thawed. The presence of these substances does not alter the performance characteristics of the product when used as a growth supplement for cell culture. This is a normal occurrence and in no way indicates that the serum has been compromised. It is not recommended to filter the serum to remove these precipitates because of the risk of losing some serum nutrients, which are essential for cell growth.

8.) Does Serum Source International reserve serum while samples are being tested?

Fetal Bovine Serum (FBS) and/or other animal serum lot reservations will be held for up to 4 weeks from the time the customer receives the samples, unless otherwise agreed upon.  Longer testing periods are available if needed, upon request by customer and approval by Serum Source International.  Serum lots are automatically released “off hold” after 4 weeks from date of delivery.

Upon completion of testing the samples, we ask that customers please contact Serum Source International to notify one of our Sales Specialists of your Fetal Bovine Serum (FBS) and/or other animal serum lot selection so that we can process your order promptly.

9.) How large are Serum Source International Fetal Bovine Sera lot sizes?

Our serum lot sizes typically range from 500-1000 liters in total (lot sizes up to 4000 L can be produced by special order). Since serum is highly comprised of natural biological material, lot to lot variability can be a concern. Large lots tend to reduce this variability and provide the best opportunity for consistency order after order.

Orders can be fulfilled in bottles sizes of 50ml, 100 ml or 500 ml.

10.)  What are other common names for Fetal Bovine Serum?

Fetal Calf Serum (FCS)
Fetal Calf Sera (FCS)
Foetal Calf Serum (FCS)
Fetal Bovine Sera (FBS)


Please contact us with any further questions.