Aqueous two-phase system was studied for the extraction of succinic acid (SA) produced by Actinobacillus succinogenes from the fermentation broth. Various hydrophilic solvents and inorganic salts were used to form the aqueous two-phase system for SA extraction, among which an acetone/ammonium sulfate aqueous two-phase system was investigated in detail, including examination of the phase diagram, effects of phase composition and pH on partitions, removal of cells and proteins from the fermentation broth, and recovery of ammonium sulfate. Under optimized conditions, with the fermentation broth pH value of 2 and aqueous two-phase system composed of 35% (w/w) acetone and 15% (w/w) ammonium sulfate, the recovery of SA from the fermentation broth was 94.4% with the removal of 93.6%, 98.1%, and 78.5% glucose, cells, and proteins, respectively. The total SA yield was 77.3% and the purity of SA was 98.7%. With the addition of methanol, 95.9% of ammonium sulfate in the salt-rich phase could be recovered, which indicated less waste discharge in SA extraction using the aqueous two-phase system. (C) 2014 Elsevier B.V. All rights reserved.