Complexation between proteins and polyelectrolytes through electrostatic interactions gives either soluble or non-soluble complexes, leading to phase separation. The formation and the stability of these complexes are influenced by pH, ionic strength, ratio between protein and polyelectrolyte and charge density of protein and polyelectrolyte. This review presented the advantages on the protein precipitation by adding a polyelectrolyte solution to a natural enzyme source (microbiological, vegetal or animal homogenate), over the classical precipitation methods. An enzyme can be precipitated like non-soluble complex, separated and then re-dissolved, thus the method works, at the same time, like concentrative and pre-purification steps together. (C) 2016 Society of Chemical Industry