The goal of this study was to determine some characteristics of Baker's yeast invertase partitioned with poly(ethylene glycol)/MgSO4 aqueous two-phase system (ATPS). Under optimized conditions [PEG-3000 (15%, w/w) and MgSO4 (23%, w/w) with 5% (w/w) MnCl2 at pH 5.0] yeast invertase was partitioned by using an ATPS with purification factor of 6.2-fold and activity recovery of 217.7%, respectively. The yeast invertase was characterised with respect to its activity and stability at various pH and temperature ranges. Optimum pH and temperature were determined at pH 5.5 and 60 degrees C, respectively. The enzyme was very stable in the range of pH 4.0-7.0 and more than 95% of its initial activity was recovered. The yeast invertase was also stable at the temperature range of 4-50 degrees C and retained nearly about 98% of its initial activity at 50 degrees C. Kinetic parameters, K-m and V-max using sucrose as substrate were measured as 24.1 mM and 35.5 U, respectively. MnSO4 and MnCl2 efficiently enhanced the activity and also showed an activator effect for invertase. Relative activities were found as 151% and 156% for MnSO4 and MnCl2, respectively. The biochemical properties of the yeast invertase partitioned in an ATPS make the enzyme good candidates for several industrial applications. (C) 2011 Elsevier B.V. All rights reserved.