Optimizing of a bioprocess for protein production is more complex than for simple increase in biomass. Over-production of biomass and normal cell metabolism may limit the amount of cellular resources directed towards making the protein of interest. This short overview lists some of the key points to take into consideration for the best yield of proteins.
The optimizing of a bioprocess for protein production is more complex than for simple increase in biomass. Over-production of biomass and normal cell metabolism may actually limit the amount of cellular resources directed towards making the protein of interest. A phased approach, with growth being followed by induction of protein manufacture and a change in operating parameters is often best. This change can be triggered at a certain biomass level by a chemical, by a change of feed or a change in a physical parameter such as temperature. The genetic changes made to optimize protein production may adversely affect the cells in terms of growth rates and sensitivity to environmental conditions e.g. heightened shear sensitivity.
The production phase may need careful control of the supply of nutrients to ensure unwanted metabolic pathways are not activated. An example is an excess of glucose leading to alcohol production in some yeasts. The culture conditions must also be maintained in a way which stops any protein produced from being damaged by denaturation or destruction from enzymes released by lysed cells.
These are the key points to take into consideration for the best yield of proteins:
1. If the nutrient supply is so excessive that microbial metabolism is only geared towards growth, the microbes will not excrete any metabolites.
Managing the bioprocess as a fed-batch process can provide a remedy here. Read more about fed-batch processes.
2. Growth conditions are often not ideal for producing, say, the targeted protein.
As a result, you may need to adjust the temperature or the pH to the protein in question in order to improve protein yield and stability.
3. Does your strain can produce the desired yields when cultured in this way?
Reviewing carefully the literature ahead of time.
4. It is just as important to know whether the cultivated strain excretes toxins or growth-inhibiting substances.
Those can be produced by growth, by the disintegration of cells or by cell metabolism. These kinds of influencing factors can impair protein production over a period of a few days.
Title image by Sean McCabe. Image copyright https://seanwes.com. Used with permission.