Comparison of FBS and Other Bovine Serums
Fetal bovine serum (FBS) is the most widely used growth promoter used in cell culture. FBS contains more growth factors than any other animal serum, and also has lower levels of undesirable complements than other types of serum. FBS is also the most expensive and difficult to source serum, with prices ranging from 3x - 10x more than other bovine serum products. Growing demand, coupled with a lower supply of FBS has resulted in a volatile market for US FBS and consequently prices have increased significantly in the past few years. You can read more about the supply and demand of US FBS on RMBIO’s Expressions using this link: www.rmbio.com/fetal-bovine-serum-supply-and-demand-for-us-fbs. With the increase in US FBS prices, we have seen an increase in demand for other bovine serum products, including newborn and calf serum. This article provides a comparison among classifications of bovine serum.
The classification of bovine serum is determined based on the age of the animal from which the serum is collected. Industry standards classify US bovine serum according to the following guidelines:
- Newborn calf Serum, less than 14 days
- Formula Fed Calf Serum, less than 22 weeks
- Calf Serum, 3 weeks to 12 months
- Adult Bovine Serum, greater than 12 months
Newborn calf serum and calf serum are cost effective alternatives to FBS, and we see them used in situations where large quantities of serum are used, such as fermentation processes and vaccine production. Research and diagnostic users of bovine serum often consider non-FBS options for their cell culture medium as well. Newborn calf serum and calf serum are most often used in situations where the cell line is robust and thus less demanding.
Total protein levels, IgG, and endotoxin, along with price, are the most common attributes our customers consider in their evaluation of serum. The following chart shows the typical values for these important serum components from lots of serum we have manufactured in the past several years.
Total protein and IgG (gamma globulin) levels in bovine serum increase with the age of animal the serum is collected from. The USP guidelines specify that total protein levels in FBS are less than or equal to 4.5g/dL, but the standards do not call out protein specifications for the other categories of bovine serum.
The total protein in serum is measured by taking a chemistry panel of the serum. While there are numerous proteins in bovine serum, the most abundant is bovine serum albumin (BSA). Some serum applications, like vaccine production, require a reduction or complete removal of bovine protein from the final product. In those instances lower levels of protein make for less work which is one reason RMBIO has seen an increase in newborn calf serum demand recently. Historically newborn calf serum has been priced enough higher than calf serum that many users opted to spend the additional resources removing the extra protein in order to realize the cost savings. This cost-benefit analysis has changed recently though as market dynamics have caused the price of calf serum higher than newborn.
IgG levels increase significantly from FBS to the other bovine serum products. Some serum users work to reduce IgG levels in order to eliminate interference, others purchase serum that has been further manufactured using proprietary chromatography techniques that result in low IgG FBS. To learn more about Low IgG FBS follow this link: https://www.rmbio.com/basics-of-igg-depleted-or-low-igg-fetal-bovine-serum-fbs
Endotoxin levels are largely impacted by the collection methods, equipment used in the serum collection and the efficiency of the serum filtration. Endotoxin levels are measured with a LAL gel clot assay that uses horseshoe crabs, although there is some momentum building for the use of PTS chromogenic readers to measure endotoxin levels of serum.
Most customers end up sampling lots of serum before making a determination of which lot to purchase. The decision to use a non-FBS bovine serum is largely a determination of cost-benefit of the growth promotion versus of the cost. While FBS remains the most popular choice of bovine serum in terms of sheer numbers of users, RMBIO has seen a shift in the percentages of our customers sampling and ultimately purchasing other options like newborn calf serum, calf serum and Fetalgro. Understanding some of the differences among the serum options may help users decide if one they should consider testing one or more of the alternatives to FBS that RMBIO manufactures.