Albacore tuna (Thunnus alalunga) spleen trypsin partitioning in an aqueous two-phase system and its hydrolytic pattern on Pacific white shrimp (Litopenaeus vannamei) shells

Partitioning behaviors of trypsin from the spleen of albacore tuna (Thunnus alalunga) in an aqueous two-phase system (ATPS) were investigated. Partitioning behaviors of proteins were influenced by polyethylene glycol (PEG) molecular mass and concentration, types and concentration of salts, NaCl concentration, and temperature. Trypsin was preferentially partitioned into the PEG-rich top phase. The best ATPS conditions for trypsin partitioning from albacore tuna spleen were 15% PEG 4000-15% NaH2PO4 at 40 degrees C without the addition of NaCl, which increased the purity by 5.54-fold with the recovered activity of 71.92%. Based on SDS-PAGE, the enzyme after ATPS separation was near homogeneity and the result of SDS-substrate gel electrophoresis revealed that the band intensity of enzyme in ATPS fraction increased, indicating the enhanced specific activity of splenic extract. The study further investigated the effect of fractionated trypsin on the hydrolysis of Pacific white shrimp (Litopenaeus vannamei) shells. Electrophoretic study revealed that trypsin after ATPS separation was a potential enzyme for extraction of carotenoprotein from Pacific white shrimp shell waste. Therefore, ATPS was an effective method for purification and recovery of trypsin from the spleen of albacore tuna and it could be used as an alternative cheap proteinase for the extraction of carotenoprotein from shrimp shells.