Journal of Food Processing & Technology

Abstract

Partition of Pepsinogen from the Stomach of Red Perch (Sebastes marinus) by Aqueous Two Phase Systems: Effects of the Salt Type and Concentration

Lisha Zhao, Suzanne M. Budge, Abdel E. Ghaly, Marianne S. Brooks and Deepika Dave

An important acidic protease, pepsin is synthesized and secreted in the gastric membrane in an inactive state called pepsinogen (PG) and has applications in the food and manufacturing industries, collagen extraction, gelatin extraction and in regulating digestibility. Fish processing waste can be used to produce commercially valuable byproducts such as pepsinogen. In the present study, the purification of pepsinogen from the stomach of red perch using aqueous two phase systems (ATPS) formed by polyethylene glycol (PEG) and salt at 4°C was optimized. The effects of salt type (MgSO₄, (NH₄)₂SO₄, Na₃C₆H₅O₇ and K₂HPO₄) and concentration (6, 7, 8, 9, 10, 11, 12, 13, 15, 17, 19%) on the partitioning of PG were studied and parameters including total volume (TV), volume ratio (VR), enzyme activity (AE), protein content (Cp), specific activity (SA), partition coefficient (Kp), purification fold (PF) and recovery yield (RY) were evaluated. Salt type and salt concentration had significant effects on each parameter. MgSO₄, (NH₄)₂SO₄, Na₃C₆H₅O₇ and K₂HPO₄ required different critical salt concentrations (9, 12, 12 and 10%, respectively) to form biphasic systems. TV and VR decreased with increased salt concentration since salt formed hydrogen bonds with water molecules and created a more compact and ordered water structure. AE, CP, SA, PF and RY showed a maximum increase with intermediate salt concentration, while KP had the opposite pattern. The highest TV and AE values were obtained at 12% (NH₄)₂SO₄ while the highest SA and PF values were obtained at 12% MgSO₄. The highest TV and Cp values were obtained at 12 and 15% Na₃C₆H₅O₇, respectively. (NH₄)₂SO₄ at 15% concentration gave the highest RY (71.7%) and was selected as the optimum salt type and concentration. Thus, 15% (NH₄)₂SO₄ 18% PEG 1500 was the optimal ATPS combination and presented the best partition. The values of SA and PF and RY obtained with ATPS method were two fold higher than those obtained with the ammonium sulphate fractionation (ASF) method.