Purification of protease from dry fermented sausages by aqueous two-phase system

Aqueous two-phase system (ATPS) was used in the purification of proteins in recent years. It was widely used for extracting the bioactive substances. In order to extend the application for analyzing the forming of enzymes in the dry fermented sausages, the protease was extracted from dry fermented sausages by an ATPS. The phase compositions including polyethylene glyool (PEG) molecular mass, concentration as well as types and concentration of salts affected protein partitioning were studied. ATPS comprising PEG1000 (20%, m/m) and magnesium sulfate (25%, m/m) provided the best condition for the maximum partitioning of the protease into the top phase and gave a highest specific activity (12. 37 U/μg protein) and purification fold (4.61). The yield of 85% was obtained. When Sephadex G-75 was used, it revealed that the band intensity of contaminating proteins in ATPS fraction almost disappeared and the band intensity of major protease slightly decreased. Therefore, ATPS was an effective method for partitioning and recovery of proteases from dry fermented sausages. Adjusted the pH in ATPS, there was no effect on protease extraction, while adding electrolyte has disadvantage effect.