Enzymatic Production Of Bioactive Peptides From Oyster

The thesis was about the enzymatic production of bioactive peptides from oyster and itsbioactivity associated with ACE inhibitory activity, radical scavenging effects, and the effects oncholesterol. The pilot tests were carried out based on bench experiments.The component analysis showed that the oyster meat contained gross protein 43.95%,glycogen 24.26%, and fats 10.72% based on dry base.The hydrolyzing abilities of 537 acidic protease and Alcalase were investigated. The resultsshowed that the former was superior to the latter for the production of peptides from oyster.When they are used to hydrolyze oyster meat, the former was able to provide more peptides thanthe latter with the same degree of hydrolyzation.The molecular weight (MW) distribution of hydrolysate was measured with Sephadex G-15and HPLC. The results showed that the MW distribution of hydrolysate resulted by 537 acidicprotease mainly ranged from 119 to 2365, composing of peptides with 2 to 5 amino acidsresidues.The radical (·OH,O2·-and DPPH·) scavenging effects of hydrolysates were investigated withspectrometer. The results showed that the effects of hydrolysates by 537 acidic protease weresuperior to those by Alcalase except for the effects on O2·-. The IC50 of the former were 3.9mg/mL, 58mg/mL, 8.08mg/mL respectively for the effects on ·OH,O2·-and DPPH·. No significantdifference were observed in the ACE inhibition capability.The IC50 of hydrolysates by 537 acidicprotease for ACE inhibition was 0.73mg/mL.537 acidic protease was preferentially used for industrial production considering the overalltechniques and bioactivities of the hydrolysate. The optimal conditions for the production ofbioactive peptides by 537 acidic protease were: pH3.0~4.0, 40℃, E/S=6% and 4 hours. Thedegree of hydrolyzation could be controlled between 16% and 20%.Nanofiltration with MWCO150 membrane was used to separate and concentrate peptides fromhydrolysate. No significant changes were observed in terms of composition, functional property,molecular weight distribution, and contents of amino acids before and after nanofiltration. Itindicated MWCO150membrane could efficiently hold the active components.In vivo experiments, the serum total cholesterol of mice fed with the bioactive peptidesproduced as above with the dosage of 0.1g/kg per day was significantly decreased, reaching47.85% after 30 days.The feasibility of techniques were confirmed by pilot tests. The product mainly containedprotein 58.77%, glycogen 18.62%, rich in minerals. It also contained trivial noxious elementssuch as Hg, Pb, As, whose contents were all within the limitation range of state standard.Key words: oyster bioactive peptides, enzymatic hydrolyzation, the radical scavenging effects,ACE inhibitory activity, hypocholesterolemic activity, membrane separation...