This invention focuses on a novel process in which Porphyridium cruentum biomass first undergoes a stage of cellular disruption and subsequently stages of recovery and purification in order to achieve the purified B-phycoerythin (BFE) protein dye, using isoelectric precipitation and two-aqueous-phase systems. The steps of recovery and purification include isoelectric precipitation followed by a step of liquid/liquid extraction by means of two-aqueous-phase systems that use polyethylene glycol (PEG) and phosphate salts. The BFE protein dye obtained in the two-aqueous-phase extraction step undergoes an ultrafiltration step in order to remove the polymer (PEG) and to obtain a dye with a purity greater than 4.0 defined as the relationship between the absorbencies at 545 and 280 nm (BFE purity=Abs 545 nm/Abs 280 nm).