Advantage vs. Disadvantage of Bacterial Expression System
Advantage of bacterial cells
- Simple physiology
- Short generation times, as bacteria grow and multiply rapidly
- High yield of product - up to 10 % of mass (low cost)
With B. subtilis and some others, it is possible to induce secretion of a gene product into the surrounding medium. This method is in use in the pharmaceutical industry in the production of hormones such as insulin and human growth hormone.
Disadvantage of bacterial cells
- Activity. The expressed proteins often do not fold properly and so are biologically inactive.
- Toxicity. The synthesized proteins are often toxic to bacteria preventing the cell cultures from reaching high densities. A solution to this problem is to incorporate an inducible promoter, which may be turned on to transcribe the inserted gene after the culture has been grown
- Modification. Lack of enzymes responsible for post-translational modifications (effect on function of proteins), eg if the protein to be expressed is a glycoprotein, there is no apparatus in the bacterium to attach the necessary sugar residues. In this case, mammalian cell expression system is the best choice.
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