Biotechnology and Bioinformatics (1+1)

9.1.5 Bioseparation

Although a large quantity of work has been done on fermentation and other upstream processing, the main cost of making a biotechnological product is the downstream processing or separation steps.

After a product has been made by a cell, it must be separated from the rest of the by-products.

• The standard industrial techniques for separating cells from spent medium are centrifugation and cross-flow filtration.
• If the cell product is an intracellular product, the cells have to be lysed through homogenization or osmotic shock.
• Bacterial cells like E. coli typically do not secrete protein products, whether mammalian cell typically will. The expensive part is that the further purification of the product, nor the initial separation of cells from product.
• Precipitation of all cellular protein is a common first step.
• A number of technologies exist for further product separation, including differential precipitation, affinity and other types of chromatography, electrophoresis, liquid-liquid extraction and use of specialized membranes.

As essential step in downstream processing is

• quality control,
• the assessment not only of sterility,
• absence of genetic materials such as viruses or nucleic acids, and
• absence of pyrogens,
• but also of the purity of the final product, such as the desired protein.