Study On The Properties Of Alginate Enzymolysis Product Degraded By Alginate Lyase And Its Derivatives

In this study,alginate was used as raw material to obtain alginate enzymolysis product(AEP)by enzymatic degradation using alginate lyase obtained from Acinetobacter junii,which was isolated in our laboratory.After classification,AEP were acetylated with acetyl,aiming to get AEP with optimized antioxidant activity and moisture retention activity.The results were as follows:(1)Degradation of alginate solution with high concentration by acid pretreatment-enzymatic degradation and enzymatic degradation methods were compared.The results showed that,after degraded for 10h,the viscosity,degree of hydrolysis(DH),yield of reducing sugar of these two products were 8.6 mpa·s and 2.9 mpa · s,35.1%and 54.7%,and 16.0%and 28.0%,respectively.Compared with acid pretreatment-enzymatic degradation method,the method of enzymatic degradation had advantages of simple process,fast degradation speed and high yield.(2)Degraded alginate solution was analyzed by HPLC,and was separated according to different molecular weight.The results showed that the product was simple in composition.The products of enzymatic degradation were separated by nanofitration to obtain alginate enzymolysis product A with Mw greater than 8kDa(AEP-A)and alginate enzymolysis product C with Mw less than 8kDa(AEP-C).(3)The activities of antioxidant,moisture retention and moisture absorption of AEP-A and AEP-C were determined and compared with AEP-B.The product of enzymatic degradation without separation was defined as AEP-B.The results showed that three kinds of products showed certain antioxidant activities in a concentration dependent manner.AEP-C showed the highest DPPH radical-scavenging activity,and the IC50 of it was 0.53mg/mL.Under the same concentration,AEP-C showed higher hydroxyl free radical scavenging activity than Vc(P<0.05).AEP-C also showed significant higher reducing power than AEP-A and AEP-B(P<0.05).These result showed that the products obtained by enzymatic degradation of sodium alginate by alginate lyase have antioxidant activities,and among,AEP-C(Mw<8000)showed the strongest activity,indicating that the products with smaller molecular weight have better antioxidant activities.The order of moisture retention and moisture absorption in RH 81%was AEP-C>AEP-B>AEP-A.Moreover,the moisture retention and moisture absorption of AEP-C were superior to the common moisturizing agent PEG-400.So AEP-C has potential as a humectant(4)Using acetic anhydride as reagent,AEP-A and AEP-C were modified with acetyl.AAEP-A and AAEP-C were products obtained from acetylation.Analysis of products showed that acetyl content of AAEP-A and AAEP-C were 11.3%and 2.9%,respectively.After study on biological activity of AAEP-A and AAEP-C,it was found that IC50 values of AAEP-A and AAEP-C on scavenging DPPH·were 0.54 and 0.25 mg/mL.The scavenging rates were significantly higher than those in non-acetylated samples.In addition,the reducing power of AAEP-A were significantly higher than that of AEP-A(P<0.05).Acetylation modification also leaded to the improvement of oxidation resistance,moisture retention and moisture absorption of AAEP-A and AAEP-C.Among them,the effects of AAEP-C on moisture retention in dry environment were close to and even slightly higher than that of glycerol.Thus,acetylation modification can effectively improve the antioxidant activity,moisture absorption activity and moisture retention activity of alginate enzymolysis products.