Studies On The Purification And Properities Of Antioxidant Peptides From Scallop By-products

Scallop is an important dominant species in mollusk with high values in our country.Plenty of by-products are produced during scallop’s traditional roughing processes.Only few of the by-products are sold as fodder at low price,and most of them are discharged,which caused the waste of resources and severe environmental pollution.As a matter of fact,scallop by-products are ideal materials for the preparation of bioactive peptides,which contained protein,amino acids and other nutrients.Compared with the synthetic antioxidants,natural antioxidant peptides not only can remove the superfluous free radicals to maintain the health of human bodies,but also are safe and efficient.This paper studied the preparation,purification and biochemical properties of antioxidant peptides from Mimachlamys nobilis by-products.The separation of antioxidant peptides from scallop by-products could decrease environmental contamination,improve the added value of seafood and promote the development of aquatic products processing industries.In this research,the DPPH,hydroxyl and superoxide anion radical scavenging activities of Mimachlamys nobilis waste enzymolysis products hydrolyzed by five commonly used commercial proteases were measured,and trypsin was chosen as the optimal protease.Single factor experiments that analyzed the effects on the antioxidant capabilities of the hydro-lysates were conducted to optimize the enzymatic hydrolysis process of scallop by-products.On the basis,the optimum hydrolysis conditions were solid-liquid ratio 1:1.5,enzyme dosage 1 000 U/g,pH 7.0,temperature 40 ℃ and time 4.5 h,according to the results of the orthogonal test.Under these optimum conditions,the DPPH,hydroxyl and superoxide anion radical scavenging activity were 75.6 %,78.5 % and 76.7 %,respectively,and the yield of soluble peptides was 73.4 %.The hydro-lysate of Mimachlamys nobilis by-products prepared under the optimal conditions was purified using ultrafiltration（10 kDa,3 kDa）,gel filtration chromatography（Sephadex G-25,G-15）,SDS-PAGE and RP-HPLC,successively.According to the results of radical scavenging activity,and one single chromatographic peak was finally obtained.Consequently,the highly-purified by-products antioxidant peptides was collected and named MNAP.Compared with the hydro-lysates,MNAP exhibited stronger antioxidant activity（85.7 %,82.4 % and 86.9 %,using DPPH,hydroxyl and superoxide anion radical scavenging activity assays,separately）.The peptides（MNAP）were composed of two peptides with their molecular weights 2855.6 Da and 3007.2 Da using MALDI-TOF-MS,respectively.The biochemical properties were measured and analyzed by a few methods.MNAP had good solubility in the range of pH 4.0¹0.0,which was higher than 88.0 %.MNAP also had good water absorption and waterholding capability,however,its foaming capability and foaming stability were poor.MNAP showed good antioxidative stability at 0⁶0 ℃,and its antioxidant activity was highest at 40 ℃.Besides,MNAP exhibited high antioxidant capability at pH 4.0¹0.0,and it got the best antioxidative stability at p H 7.0.Moreover,different metal ions could affect MNAP’s radical scavenging capability in different extents,including Mg²⁺,Zn²⁺,Cu²⁺,which had the greatest influences on the antioxidant activity.In this paper,the optimum hydrolysis conditions of antioxidant peptides from scallop by-products were established.Based on this,the fraction from scallop by-products with the highest antioxidant capability were then purified and filtered using various efficient ways.And the biochemical properties of the purified antioxidant peptides were analyzed and compared.The above research supplied important theoretical basis to industrial production and practical production,and application of antioxidant peptides from scallop by-products.