Question

What are the steps involved in downstream processing?

Answer 1

Downstream processing: It is a technique used for the recovery and purification of biosynthetic substances, such as pharmaceutical or recombinant DNA products.

It consists of the following stages:

1. Solid-Liquid Separation- Whole cells and other insoluble substances are separated from the fermentation broth. this is done using methods like flotation, filtration, flocculation, centrifugation, gravity settling, etc.
2. Release of Intracellular Products- Several vitamins and enzymes present in the cells are released in their active state for further purification and isolation. Other cells and microbes are disrupted using physical, chemical, or enzymatic methods.
3. Concentration- The product that is to be extracted is a very small concentration. The filtrate that is free of cells and other impurities still contains a large concentration of water (~80-98%) which needs to be removed to obtain the final product concentration. Some of the methods used are evaporation, precipitation, liquid-liquid extraction, adsorption, and membrane filtration.
4. Purification by Chromatography- Chromatography is used to separate biological products having similar properties effectively. Some of the chromatographic techniques include gel-filtration, ion-exchange, affinity chromatography, and hydrophobic interaction.
5. Formulation- This step is necessary to maintain the activity of the biological products during storage. For example, in the case of proteins, stabilizing agents such as sugars, salts, and polymers are used. they are formulated as dry powders, solutions, or suspensions.