Recombinant protein expression enables the production of biological therapies, vaccines, or ancillary reagents, among others. A critical decision in any project is the choice of the right host system, as each comes with advantages and disadvantages that can impact yield, quality, and cost. In this article, we explore the most commonly used host systems in recombinant protein production.
Bacteria: A Versatile and Efficient Option
Regarding bacterial hosts, we will analyze the two most commonly used: E. coli and Bacillus subtilis. According to various studies, bacteria are the most frequently chosen systems due to their rapid growth and scalability.
Escherichia coli is one of the most widely used host systems for recombinant protein expression due to its fast growth, ease of genetic manipulation, and low cost. This organism can achieve high production yields in a short time, making it ideal for projects requiring speed and scalability. However, one major challenge with E. coli is its inability to perform complex post-translational modifications, such as glycosylation, which are essential for the activity and stability of certain biotherapeutic proteins. Additionally, proteins expressed in E. coli are often found in the form of inclusion bodies, requiring additional steps for solubilization and refolding. Endotoxins present in the cell membrane can also limit its application in human biopharmaceuticals.
Bacillus subtilis is another bacterial host popular for protein production, particularly due to its ability to secrete proteins directly into the culture medium, simplifying recovery and purification. Furthermore, this microorganism does not produce endotoxins, making it an attractive option for therapeutic applications. Nevertheless, Bacillus has some limitations, such as the production of proteases that can degrade recombinant proteins, and its genetic manipulation is more complex compared to E. coli.
Yeasts: Balancing Productivity and Post-Translational Modifications
For yeast-based systems, two species stand out: Pichia pastoris and Saccharomyces cerevisiae. Yeasts are widely recognized for their balance between cost-effectiveness and their ability to perform post-translational modifications. Pichia pastoris is a widely used host system for recombinant protein expression due to its ability to grow to high cell densities in bioreactors, increasing productivity. It can perform certain post-translational modifications, such as glycosylation, that are not possible in bacteria. This makes it an ideal choice for proteins requiring proper folding and biological functionality. However, the glycosylation patterns in Pichia differ from those in mammalian systems, which can limit its use for some biopharmaceutical products. Additionally, the use of methanol as an inducer for the most common promoters involves higher operational costs and safety considerations.
Known as baker’s or brewer’s yeast, Saccharomyces cerevisiae is one of the most studied and utilized systems in biotechnology. It offers the ability to perform post-translational modifications and has been approved for the production of numerous biologics, including vaccines. However, S. cerevisiae tends to hyper-glycosylate proteins, which can be problematic for certain therapeutic products. Additionally, its secretion of proteins into the medium is limited, complicating purification.
Filamentous Fungi: High-Yield Production
When discussing filamentous fungi, two key systems are Trichoderma reesei and C1 (Myceliophthora thermophila). These systems are especially noted for their capacity to produce industrial enzymes. Learn more about the C1 platform’s innovative capabilities on Dyadic’s official website. Trichoderma reesei is renowned for its high secretion capacity, making it ideal for industrial applications requiring mass production. Its ability to produce industrial enzymes is well-recognized.
Like Pichia pastoris, Trichoderma exhibits glycosylation patterns that differ from mammalian systems, limiting its use in pharmaceutical products. Moreover, its genetic manipulation is more challenging and requires advanced techniques.
The C1 system is a promising filamentous fungus due to its ability to produce exceptionally high amounts of protein. Its simple cultivation requirements reduce operational costs. Despite its advantages, C1 is relatively new compared to other host systems, which may lead to hesitancy in adoption due to a lack of validation in certain applications.
Choosing the right host system for recombinant protein expression depends on several factors, as a summary:
At 53Biologics, we specialize in customized strain development to optimize protein expression across various host systems. To learn more about our services and how we can help you achieve your goals, visit our Strain Development page.
About 53Biologics:
53Biologics is a Spanish CDMO specialized in decoding biologics production, from DNA to proteins. The company provide services from preclinical development to GMP manufacturing, supporting their clients in getting their biological products to market as quickly as possible.
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