Direct precipitation

This is very uncommon, but there are two examples. The early method for purification of the antibiotic cycloserine was to add silver nitrate to the clarified fermentation broth to precipitate its insoluble silver salt. This was far too expensive, and alternate methods were soon discovered. Furthermore, the dry silver salt could explode.

Example #2 is the recovery of proteolytic enzymes that are used in detergents. It seems crazy to add acetone directly to the fermentation broth. Some yield is lost because of enzyme instability in acetone, and the volumes of solvent are enormous. However, other methods of recovery tend to be even worse in terms of cost.

There is an interactive exercise for the topic of crystallization that is worth running here. Adding solvents