The extraction and purification of phycocyanin from Calothrix sp., cyanobacteria isolated from rice fields in Cuernavaca, Morelos, Mexico is described. Phycocyanin was extracted with 2 mg of lysozyme/g wet biomass, and purified by anion chromatography using Q-Sepharose fast-flow (Pharmacia(R), 1.5 cm x 10 cm) column and hydrophobic interaction chromatography with methyl macro-prep (Bio-Rad(R), 1.5 cm x 20 cm) column. The purified protein showed a pl of 5.2 and has two subunits with apparent molecular mass of 21-17 kDa each. The estimated molecular mass of native purified phycocyanin was 114 kDa, suggesting a stereochemistry Of (alphabeta)(3). (C) 2003 Elsevier Ltd. All rights reserved.