Effect of salts and polyethylene glycols on the partitioning and recovery of trypsin from hybrid catfish viscera in aqueous two-phase systems.

ABSTRACT The partitioning behavior of trypsin from hybrid catfish viscera in aqueous two-phase systems (ATPS) was studied. Factors such as polyethylene glycol (PEG) molecular mass and concentration, as well as types and concentration of salts, affected protein separation. Trypsin partitioned mainly in the top PEG-rich phase. ATPS formed by PEG of molecular weight 4,000 (20%, w/w) and NaH2PO4 (20%, w/w) showed the best capability for trypsin purification from hybrid catfish viscera. Under such conditions, the highest specific activity (30.05 units/µg protein) and purification (27.3-fold), were obtained. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the enzyme after ATPS separation was near homogeneity and based on the activity staining, the band intensity of enzyme in ATPS fraction increased, indicating the greater specific activity of the viscera extract. The partitioned enzyme displayed optimal activity at pH 9.0 and 50C, respectively. The enzyme was stable up to 40C and within the pH range of 8–12. The enzyme exhibited a progressive decrease in activity with increasing NaCl concentration. PRACTICAL APPLICATIONS This paper describes the separation and recovery of trypsin from hybrid catfish viscera in ATPS and its properties. ATPS provides an efficient and attractive method for partitioning and recovery of trypsin from hybrid catfish viscera. Trypsins from various sources catalyze the hydrolysis of peptide bonds on the carboxyl sides of arginine and lysine. Therefore, it is expected that like other trypsins, trypsin after ATPS separation from hybrid catfish viscera could be useful in the biomedical, food and beverage industries.