Study On Treatments Of Alginate By Alginate Lyase Catalysis And The Performance Of Their Products

Alginate lyase was prepared by Acinetobacter junii selected from seaweed. Studies on the properties of alginate lyase showed that the optimal temperature and pH of enzyme degredation were 31℃ and 8.0 respectively, which were within the range of their stability. These properties would make it easier for preparing alginate oligosaccharide by degrading alginate in its industrial applications.When 50% ethanol (V/V) was added, the enzyme-catalyzed reaction was stopped timely, which indicated that addition of ethanol could keep the structure of alginate oligosaccharide stable. The viscosity of alginate solution decresed rapidly during the degrading alginate, thus 0.5% alginate was added every 1h from the began of the reaction. When the concentration of alginate reached 3.5%, the amount of alginate oligosaccharide was improved, and reached to 9.28mg/mL. The results showed that this method could improve the use ratio of equipments, while reducing the amount of alginate lyase.Algin oligosaccharide, with three different average degrees of polymerization (DP) which were DP3, DP4 and DP6 respectively, were prepared by time controlling. The properties of moisture retention and moisture adsorption of the three products were evaluated. The results showed that the moisture retention and moisture adsorption increased with the decreased of DP. For example, after the algin oligosaccharide with DP of 3 and glycerol were dried to constant weight, they were placed in the relative humidity with 81% for 8h, the moisture retention were 62.8% and 71.2% respectively. It seemed that the algin oligosaccharide with DP of 3 can be used as a nature moisture retention agent with great development potential in many kinds of cosmetic.The reducing power, scavenging activity against hydroxyl radical and DPPH radical of different DP were studied. The results showed that, alginate oligosaccharide with low DP seemed to have strong antioxidative activity. But when it was compared with some common anti-oxidants such as TROLOX and TBHQ, there was still some difference between them. Acetylated alginate was prepared using acetic anhydride as acetylated reagent, NBS as catalyst, and then using alginate lyase as catalyst to hydrolyze acetylated alginate in order to prepare acetylated alginate oligosaccharide. The results showed that the antioxidative activity and scavenging activity against radical increased in varying degrees. For example, when it came to the scavenging activity against hydroxyl radical, IC50 of acetylated alginate oligosaccharide Ac50 and alginate oligosaccharide were 0.375mg/mL and 0.712mg/mL respectively. Further study on acetylated alginate oligosaccharide which serves as a new kind of anti-oxidants should be continued.The structure of the alginate oligosaccharide was confirmed by IR, HPLC and ESI-MS, and the results showed that alginate oligosaccharide was a kind of trisaccharide.