The partitioning behavior of catalase from white rot fungus Phanerochaete chrysosporium has been studied in various poly(ethylene glycol) (PEG)-salt aqueous two phase systems (ATPSs). The effects of the molecular weight of the PEG, system composition and salt type besides NaCl concentration as a non-phase forming component and pH of the system on catalase partitioning were investigated at 25 degrees C. In all of the investigated ATPSs, catalase showed affinity to the top phase. The best partition parameters were found in the PEG 1000 18%-K2HPO4 12% (w/w, pH 8.2) system when there was no addition of non-phase forming salt, NaCl. For the optimized ATPS, partition coefficient of total catalase activity (K-e) and partition coefficient of total protein concentration (K-p) were determined as 10.55 and 0.21, respectively. In this system, the yield (Y-t) was found as 91.95% and the purity of the catalase enzyme from P. chrysosporium was increased to 5.72 with the recovery (R-t) of 81.96% in the top phase. The optimized ATPS proved to be a useful technique for the initial purification of catalase as an alternative to the traditional ones. (c) 2012 Elsevier B.V. All rights reserved.