Salting out

Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out)[1] is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength.

After protein folding in aqueous solution, hydrophobic amino acids usually form protected hydrophobic areas while hydrophilic amino acids interact with the molecules of solvation and allow proteins to form hydrogen bonds with the surrounding water molecules.

To separate glycerin from the soap, the pasty boiling mass is treated with brine (NaCl solution).

The slightly alkaline salt solution, termed spent lye, is extracted from the bottom of the pan or kettle and may be subsequently treated for glycerin recovery.

Thus to obtain a purer protein of interest, additional purification methods such as ion exchange chromatography may be required.