Structural Characterizations Of Marine Microbial Exopolysaccharides And Their Antioxidant Activities

The exopolysaccharides produced by marine microorganisms of special environments got much attention in the medical field for their novel structural characteristics,unique chemical properties, antioxidant activities and their potential business value. In this paper, four marine microorganisms were chosen as research objects and the yield chemical properties, monosaccharide component and antioxidant activities of the EPSs were analyzed. Base on the date of experiments, TEPS and LEPS produced by marine microorganisms Fusarium oxysporum, Dichotella gemmacea epiphytic fungi Aspergillusochraceus were further purified, their structural characteristics and antioxidant activities were studied. The research results are as follows.1: The yields of the exopolysaccharides, TEPS, AEPS, LEPS and HEPS, produced by four marine microorganisms were about 0.35 g/L,0.22 g/L,0.30 g/L,0.11 g/L, respectively. TEPS and LEPS were mainly composed of Man, Glc, Gal. LEPS, AEPS mainly consisted of Glc. The sulfate contents of the four exopolysaccharides were all below the detection limit. LEPS and TEPS were further purified by Q-Sepharose Fast Flow and Superdex S-75 column. The average molecular weight of L0S, L4S, T1S, T2S measured by Shodex OH pak SB-804 were about 5.6kDa, 5.75 kDa, 37.3 kDa and 38.0 kDa, respectively.2: The structure of L0S, L4S, T1S were studied by methylation analysis,IR,HPLC,GC-MS and NMR. The results showed that the backbone of the polysaccharide T1S consisted of→6)-β-Galf-(1→, and the side chains→2)-α-Glcp(1→,α-Glcp(1→andβ-Manp(1→were linked to O-2 of the→6)-β-Galf-(1→. The exopolysaccharide T1S was a novel branched neutral polysaccharide with galactofuranose residues. In addition, the results demonstrated that L0S mainly contained→4)-Glc-(1→, and minor amount of→6)-Glc-(1→was on the side chains, and L4S had a linear structure with[→6)-Glc-(1→].3: The three exopolysaccharides (L0S, L4S, T1S) exhibited different degrees of antioxidant activities in vitro, which were tested by DPPH radicals, superoxide radicals scavenging abilities and lipid peroxidation. L0S, L4S show stronger antioxidant abilities than T1S, and the differences of their antioxidant activies the three exopolysaccharides maybe related with their molecular weights, monosaccharide composition.