Study On Isolation And Structures Of The Exopolysaccharides From Five Marine Microorganisms

Marine is rich in microorganisms due to their special living environment. On the basis ofthe microbe habitat environment, marine microorganisms can be divided into the sea water,marine sediment, symbiotic, co-existence and deep-sea microorganisms. In this paper, fivecrude exopolysaccharides were obtained from the broth of different marine microorganismsand purified through different chromatographic separation technology. Their chemicalcharacterizations were investigated using chemical analysis methods. The structures of threeexopolysaccharides produced by two marine antinomycetes and a marine fungus were furtherinvestigated. The research results were as follows:1. The crude exopolysaccharide was obtained from the fermented broth of mangrove rootmud antinomycete Saccharopolyspora sp., and further purified by Q Sepharose Fast Flowion-exchange chromatography and Sephacryl S-100gel permeation chromatography. Twopurified exopolysaccharides, designated SSW1-1and SSW2-1, were obtained. Theirmolecular weights were17.0kDa and12.7kDa, respectively. Monosaccharide compositionanalysis by reversed–phase HPLC showed that both of SSW1-1and SSW2-1mainlycontained Man. The structure of SSW1-1was investigated by a combination of chemical andinstrumental analyses including acid hydrolysis, methylation analysis, GC-MS, IR and NMR.The result showed that the backbone of SSW1-1was mainly composed of(1�'2)-α-mannopyranose and (1�'6)-α-mannopyranose residues, and branched at C-6of(1�'2)-α-mannopyranose with (1�'3)-α-mannotetrose,(1�'2)-α-mannotetrose or terminalα-manopyranose residues. The antioxidant activities of SSW1-1and SSW2-1were evaluatedwith the scavenging abilities on DPPH radicals. The EC50values of scavenging ability ofSSW1-1and SSW2-1on DPPH radicals were2.4mg/mL and2.2mg/mL, respectively. Theresult indicated that the SSW1-1and SSW2-1possess good antioxidant activities.2. The exopolysaccharide CHQ2-1was obtained from the fermented broth of the sea mudantinomycete Streptomyces sp. and purified by Q-Sepharose Fast Flow ion-exchangechromatography and Sephacryl S-100gel permeation chromatography. CHQ2-1was amannan with molecular weight of30.7kDa analyzed by PMP-HPLC and HPGPC. According to the results of GC-MS and NMR analyses，the backbone of CHQ2-1was composed ofα-(1�'2) and α-(1�'6) residues, substituted at C-2of part of (1�'6)-α-mannopyranoseresidues with α-(1�'2), α-(1�'3) or terminal α-manopyranose residues. The EC50values ofscavenging ability of CHQ2-1on DPPH radicals was6.6mg/mL, indicating that theantioxidant activity of CHQ2-1was not obvious.3. The exopolysaccharide HDN was produced by the sponge endogeneous fungusApiospora montagnei. After purification by Q-Sepharose Fast Flow ion-exchangechromatography and Sephacryl S-100gel permeation, the exopolysaccharide HDN2-1withmolecular weight of14.7kDa was obtained. Monosaccharide composition analysis byPMP-HPLC showed that HDN2-1mainly contained Man, Gal and Rha in the molar ratio of7.6:6.3:1.0. Structural characterization was investigated using partial acid hydrolysis,methylation analysis, GC-MS and NMR analyses, and the result indicated that HDN-P was alinear mannan with α-(1�'2) and α-(1�'6) mannopyranose residues in the ratio of3:1,HDN2-1also had the same backbone chain, and branched at C-2of (1�'6)-α-mannopyranoseresidues with (1�'5)-galactofuranose, terminal mannopyranose, galactopyranose orrhamnopyranose residues. HDN2-1is an exopolysaccharide with novel structure.4. Two crude exopolysaccharides MX and HS were isolated from the fermented broth ofsponge fungus MXH-82and mangrove plant magnolia root mud fungus Aspergillus flavus inYingluo Bay of Gauangxi, respectively. Five purified exopolysaccharides MX1-1, MX2-1,MX3-1, HS1-1and HS2-1were obtained by Q-Sepharose Fast Flow ion-exchangechromatography and Sephacryl S-100gel permeation chromatography. Their molecularweights were18.2kDa,11.4kDa,24.7kDa,7.7kDa and16.2kDa, respectively. Theexopolysaccharides MX1-1, MX2-1and MX3-1were mainly composed of Man, Gal, Glc andGlcN. MX2-1and MX3-1also contained small amounts of GlcUA. The exopolysaccharidesHS1-1and HS2-1were mainly composed of Man, Glc, Gal, with small amounts of GlcN.The results provided novel marine polysaccharides for the “marine polysaccharidesdatabase”. Moreover, the study established the basis for further investigation ofstructure-activity relationship of exopolysaccharides and development of theexopolysaccharide products from marine microorganisms.