The bromelains are proteases from vegetable origin, obtained from several species of Bromeliaceae family, which are found in pineapple's stem and fruit. The bromelains uses are based on its proteolytic activity on food industries and mostly at Brazilian pharmaceutical industry. The bromelains has been documented by its therapeutic effects at all inflammatory conditions, in addition to its attested efficiency of cure of various health problems, such as angina, indigestion and respiratory problems. Various bromelains' purification methods have been studied, particularly bromelain of pineapple stem. Aqueous two-phase system has been applied for several years as a good laboratorial separation technique and it can be used as a pre-purification step. This system has been tested with large success, it is formed by two aqueous phases immiscible or partially miscible within themselves, obtained by the addition of hydrophilic polymers or one hydrophilic polymer and a salt, such as the poly(ethylene glycol) - PEG - and potassium phosphate salt systems. This work studied the enzyme characterization and recovery presented in the pineapple's stem and peel, by aqueous two-phase systems (ATPs) liquid-liquid extraction. Batch assays were performed aiming the enzyme extraction and recuperation, using the partition coefficient as indicator. The phase diagrams from PEG and potassium phosphate salts aqueous two-phase systems (ATPs) were obtained for PEG with molecular weight of 4000 at pH 6.0 to 11.0, at 25 °C. Three different tie-lines were also studied. 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