Optimization Of Preparation Process And Activity Evaluation Of Polysaccharide And Oligosaccharide From Sargassum Oligocystum

Sargassum,a common economic macroalgae located in the South China Sea,is an important source of brown algae polysaccharides.Brown algae polysaccharide and the degradation products,namely alginate oligosaccharides,have many biological activities and have broad application prospects in agriculture,medicine,cosmetics and other fields.In this paper,using Sargassum oligocystum（collected from the sea area of Qionghai,Hainan）as the research object,the methods of an effective extracting polysaccharides and enzymatically preparing alginate oligosaccharides were explored.The prepared polysaccharides and oligosaccharides were purified,structure analyzed and activity evaluated.The research results were as follows:Using ultrasonic assisted-hot alkali method,the best polysaccharide extraction process was obtained from Sargassum oligocystum by response surface optimization.The crude polysaccharide yield was 41.23%±0.98%under the conditions of ultrasonic power 500W,material-liquid ratio of 1:25,extraction time 5.95 h（including ultrasonic1 h）,extraction temperature 82.27℃,and Na OH mass fraction 3.87%.Based on TCA precipitation method,the protein removal rate of crude polysaccharide reached 81.93%and the polysaccharide retention rate was 92.17%.The H₂O₂ oxidation process was optimized and used to remove the pigment.The decolorization rate reached 91.23%and polysaccharide retention rate was 85.32%when the H₂O₂ concentration was 1.5%,decolorizing at 70℃for 6h.Three polysaccharide components SOP1,SOP2 and SOP3 were obtained on the basis of DEAE-52 ion exchange chromatography.The molecular weight,purity and content analysis of total sugar,reducing sugar,protein,sulfate,uronic acid were also determined.The crude enzyme solution was prepared by fermentation of a novel species,Paenibacillus algicola HB172198^T,and the enzyme activity of the fermentation broth was 15.20 U/ml.The enzymatic properties of the preliminary purified alginate lyase were studied.The optimal reaction conditions for the enzyme were 50℃,p H 8,and the enzyme activity was stable in the range of 4-40℃,p H 6-8.The ions of Ca²⁺,Mg²⁺and Fe²⁺could promote the enzyme activity,however EDTA,Ba²⁺and Zn²⁺could inhibit it.The optimal enzymolysis conditions of alginate were obtained.When the substrate concentration was 1.2%,the enzyme amount was 18.60 U/ml,p H value was 7.0,and the reaction time was 32 h at 45℃,the reducing sugar production was26.32 mg/L,an increase of 58.32%over the initial condition,and the average degree of oligosaccharide polymerization reached 14.19.Using the extracted brown algae polysaccharide as raw material,a large amount of alginate oligosaccharide was prepared according to the enzymatic hydrolysis process.The Bio-Gel P2 gel chromatography column was used to separate and purify the oligosaccharides and obtain seven oligosaccharide components（F1-F7）with different degrees of polymerization were obtained.The results of TLC analysis showed that the degree of polymerization was between 1-7.The results of scavenging free radicals showed that brown algae polysaccharides and oligosaccharides had strong antioxidant activity.The free radical scavenging rate increased with the increase of sugar concentration.When the concentration of oligosaccharide was 2.25 mg/m L and the concentration of polysaccharide was 2.50mg/m L,the free radical scavenging rate reached the maximum,70.48%±1.63%and64.51%±1.11%,respectively.When the concentration of polysaccharide and oligosaccharide was 2.5mg/m L,the superoxide anion radical scavenging rate reached40.07±1.06%and 54.76±0.93%,respectively.Under relative humidities of 85%and62%,both polysaccharides and oligosaccharides showed strong hygroscopicity,and alginate oligosaccharides were better.In a dry environment,both polysaccharide and oligosaccharide showed strong moisturizing effects,and the moisturizing rate of oligosaccharide reached 83.23%at 36 h,which was equivalent to hyaluronic acid.Bacteriostatic results showed that alginate oligosaccharides had a good antibacterial effect on Candida albicans,Staphyloccocus aureus,Escherichia coli and Pseudomonas aerginosa.The brown algae polysaccharide had a bacteriostatic effect on Candida albicans,but no effect on the other three bacteria.