The ideal cell culture medium would allow mammalian cells to grow at the same rate as sera without any loss in protein yield. Accordingly, many serum-free alternatives have been developed since the late 1970s.
The first step toward serum-free media (SFM) was the use of animal-derived protein hydrolysates (peptones), produced with animal-derived enzymes and/or purified proteins from animal or human sources.
In the search for a growth medium that most closely replicates the benefits of animal-derived sera without its attendant biosafety risks, there has been growing interest in the use of plant-based (vegetable) hydrolysates such as those derived from soy, wheat, and cottonseed.
Kerry Bio-Science, with its Sheffield™ Pharma Ingredients (www.sheffield-products.com) brand products, was among the first to market nonanimal-derived protein hydrolysates for both serum replacement and general media/system optimization efforts. Examples of Kerry Bio-Science products include Hy-Soy™ or HyPep™ 1510 (both derived from soy), HyPep™ 7504 (cottonseed), and HyPep™ 4601 (wheat gluten).
Various test results clearly demonstrate the suitability of vegetable protein hydrolysates to replace animal-derived media components for the cultivation of most cell lines (e.g., hybridoma, BHK, CHO, Vero, MDCK). The first biotherapeutics produced using plant-protein hydrolysates have already reached the market and many more are in various stages of development.
Nonetheless, plant-based hydrolysates have met with criticism concerning lack of definition and lot-to-lot variability. Although most suggest such variability results from key processing steps employed during hydrolysis and refinement, the raw material itself—be it seasonal effects in plant crops or intrinsic differences among specific enzyme activities—can also contribute.
One possible solution has been the use of chemically defined growth media (CDM), which attempt to optimize individual biochemical formulation constituents without the need to supplement with a protein hydrolysate. Although CDM has had its successful applications, development and optimization time lines can be long and expensive, process performance may be somewhat limited (yield loss, culture viability concerns), and formulation utility or versatility may well prohibit the development of a platform CDM suitable for both wild-type host cells and their bioengineered progeny.
Despite advances in SFM and CDM, some particularly fastidious yet industrially important mammalian cell lines seem to still require serum components (e.g., attachment factors) to perform in a viable culture.
Sheffield Pharma Ingredients has developed a new hydrolysate platform that addresses the need for animal-free cell culture medium supplements while also minimizing variability concerns. The platform is based upon a novel approach to enzymatic digestion and more refined processing.
At the heart of the product is a rationally designed nonanimal enzyme cocktail, including both proteases and nonproteolytic enzymes, whose activities can also liberate primary components of the polymerized nonprotein portion of the raw material. This enzyme blend is added during a highly optimized process step that targets specific enzyme-substrate reactions to expand the range of beneficial nutritional factors made available to cells in culture.
Such factors are fundamental to improving the bioperformance of the culture system, as they provide not merely growth-promoting peptides and amino acids, but also key carbohydrates, lipids, minerals, and vitamins that improve both rate and quality of protein expression and serve to improve culture life due to osmoprotectant and antiapoptotic properties.
Also of significant note is that, compared to typical hydrolysates, the production process is greatly reduced and requires fewer steps, intrinsically yielding a better-controlled and therefore more reproducible product.
Finally, the more sophisticated approach to enzymatic digestion renders hydrolysates more amenable to sterile filtration, allowing hydrolysate end users to experience streamlined media preparation and bioreactor supplementation activities.
UltraPep™ Soy, the first commercial product manufactured using this process, was released earlier this year.