Study On The Production Of Oligopeptide From Fish Waste

In this paper, study on preparing higher value-added bioactive oligopeptide by double-enzymes hydrolysis technique and membrane technology from low-value Hypophthalmichthys molitrix and fish waste were carried out, the kinetic model between degree of hydrolysis (DH) and hydrolysis time in the process of double enzymatic hydrolysis was discussed, and also a preliminary study of antioxidant activity and angiotensin-converting enzyme (ACE) inhibitory activity of hydrolysates were carried out.The study on single-enzymatic hydrolysis of Hypophthalmichthys molitrix protein showed that Protamex, Alcalase and Flavorzyme were more suitable for Hypophthalmichthys molitrix enzyming, single-factor experiment results show that the optimal hydrolysis conditions of Protamex,Alcalase and Flavorzyme were as follows: the optimal substrate concentration was all 4.5%, the best pH were 7,7.5,7, hydrolysis time were 180min,120min,120min, the amount of enzyme (mass ritio of enzyme and protein) were 3%,3%,4%, temperature were 50℃,55℃,50℃respectively, DH were 17.7%,20.2%,19.3% and nitrogen utilization were 86.1%,92.4%,92% respectively in the best conditions of each protease.Taking DH,nitrogen utilization and molecular weight distribution as indexes in order to compare the hydrolysis ability of these three double-protease, the single-factor experiment were tested under their optimum conditions, for integrated consideration, Protamex,Alcalase was determined as the best double-enzyme group. DH is 21.9%; nitrogen utilization rate is 95%,98% molecular weights are below 1000Da with this optimal hydrolysis system.The model between DH and time (t) in Hypophthalmichthys molitrix protein hydrolysis system by Protamex and Alcalase was discussed. The model was described as:DH=1/b In [1+axbxt] sustained by experiment result, data fitting and theoretical analysis, where the parameters a=1.03356e/s-0.19043, b=0.23449, e/s is the quality percentage of amount of enzyme and substrate protein.The preliminary study on antioxidation and ACE inhibitory activity of hydrolysates were discussed. The results showed that all hydrolysates of each DH have ability to remove·OH, while the hydrolysates of DH20% had best ability; The hydrolysate of DH5% had the highest antioxidation capacity while the hydrolysate of DH25% had the lowest antioxidation capacity for the total antioxidation capacity; The hydrolysate of DH20% had the highest rate of ACE inhibition, and all the hydrolysates had inhibition of ACE at each DH.The study on different micro-filtration membrane and nano-filtration membrane showed that micro-filtration membraneⅡand nano-filtration membraneⅡhad better performance for hydrolysate of Hypophthalmichthys molitrix. The results showed that micro-filtration membrane II had better impurity removing and the purity of oligo-peptide was increased about 4%.The purity was increased to 94.2% and the hydrolysate was concentrated 9.3-fold by nanofiltration membraneⅡ.