Downstream processing

After making the product in a fermenter, one might assume that the work is done. But this is not so; we have just begun. The production of biomolecules is governed by the aqueous environment needed for microorganisms. The product can be the micro-organism itself, or a metabolite excreted in the solution or contained in inclusion bodies, but the fermenter may contain up to 95% water and much effort has to be put in concentrating the product. There is a correlation between the concentration of a product in the broth and its price in the marketplace. The more dilute a product, the higher the cost prize. Removal of water is one thing, there are many additional problems in downstream processing (DSP). The product may be intracellular and the cells have to be disrupted to release the product. The fermenter fluid may be complex containing compounds resembling the product, which makes it difficult to purify the product. Even so, a high purity may be needed: in pharmaceutical products up to 99.999% purity is required. These problems govern the approach used to separate the product.