Digestive enzymes characterization of krill (Euphausia superba) residues deoiled by supercritical carbon dioxide and organic solvents

In this study, Enzyme activities of krill were characterized before and after lipid extraction by supercritical carbon dioxide (SC-CO₂) and organic solvent, n-hexane and acetone. Krill SC-CO₂ extraction was performed under the conditions of temperature range from 35 to 45 °C and pressure, 150–250 bar for 2.5 h with a constant flow rate of 22 g/min. Extraction yields of lipids increased with pressure and temperature. The digestive enzyme activities of protease, lipase and amylase of SC-CO₂ treated krill residues were slightly decreased comparing to organic solvent, n-hexane and acetone treated residues. In SC-CO₂ treated samples, all of the digestive enzymes showed slightly higher temperature stability. In the other hand the crude extracts of SC-CO₂ and n-hexane treated krill samples showed almost same optimum pH and pH stability for each of the digestive enzymes. It was also found in SDS-PAGE that there are no significant differences in protein patterns of the crude extracts of untreated, SC-CO₂, n-hexane and acetone treated krill indicating no denaturation of proteins.