Extraction and purification of amyloglucosidase (AMG) using aqueous two phase systems (ATPSs) composed by polyethylene glycol (PEG, average molar mass of 4000 g/mol) and sodium polyacrylate (NaPA, average molar mass of 15,000 g/mol) has been studied. Phase equilibrium diagrams were obtained at pH 6.0 and 9.0, which were used for partitioning studies. The selectivity (S) and partition coefficient (K-e) of AMG were evaluated as a function of pH, temperature and concentration of PEG and NaPA, and it was found that these parameters were affected by pH and NaPA concentrations. A face-centered design with the response surface methodology was applied for selectivity optimization. The highest value found for S was 1.6 at pH of 6.5, temperature of 25 degrees C, PEG concentration of 12.5% (w/w) and NaPA concentration of 11.4% (w/w). The corresponding K-e was 2.0. The purification factor (P-F) and the recovery yield (Y) were determined as 1.9% and 86%, respectively. (C) 2013 Elsevier B.V. All rights reserved.