| Marine microorganisms are recognized as an abundant source of bioactive substances. In recent years, the interest in extracellular polysaccharides produced by marine microorganisms is increasing. The diversity of marine microorganisms determines the diversity of extracellular polysaccharides. The extracellular polysaccharides produced by marine microorganisms hold a great potential application in food and pharmacology. In this paper, water soluble extracellular polysaccharides from a marine fungus and two deep-sea actinomycetes were investigated. The extracellular polysaccharides from the liquid culture broth were isolated and purified by ethanol precipitation, anion-exchange and size-exclusion chromatography. The physicochemical properties and structural characterizations of the extracellular polysaccharides were studied by a variety of chemical methods and modern analytical technologies. The results were as follows:1. Crude extracellular polysaccharide OUC was obtained from the fermented broth of the mangrove root mud fungus Aspergillus sp. OUCMDZ-1914 by ethanol precipitation, and purified by Q-Sepharose Fast Flow column chromatography and Sephacryl S-100 column chromatography. The four purified polysaccharides. designated ouc-1, ouc-2, ouc-3 and ouc-4 were obtained. Total sugar content was measured by the phenol-sulfuric acid method, protein content was assayed by Bradford method, and amino sugar content was measured by improved Ehrlich method. The results showed that total sugar contents of the four purified polysaccharides were very high and protein contents were low. Monosaccharide composition analysis by reversed-phase HPLC showed that ouc-1, ouc-2, ouc-3 and ouc-4 mainly contained Man with small amounts of Glc and Gal, and ouc-2, ouc-3 and ouc-4 also contained GlcN. HPGPC analysis indicated that the four polysaccharides were purified, and the molecular weights of ouc-1, ouc-2, ouc-3 and ouc-4 are 2.9 kDa,4.26 kDa,3.7 kDa and 4.1 kDa, respectively. The results of IR and methylation analyses demonstrated that ouc-1, ouc-2, ouc-3 and ouc-4 mainly consisted of four kinds of linkage type units:Manp(1â†',â†'2)Manp(1â†',â†'3)Manp(1â†',â†'6)Manp(1â†',and â†'2,6)Manp(1â†', ouc-3 also contained Galf(1â†' and â†'4)Glcp(1â†', and â†'4)Glcp(1â†' was also found in ouc-4.2. Crude extracellular polysaccharides MDZ and SH were isolated from the fermentation liquid of deep-sea actinomyces oucmdz-2984 and oucmdz-3763. respectively. Five extracellular polysaccharides, mdz-1, mdz-2, sh-11, sh-12 and sh-2 were obtained by Q-Sepharose Fast Flow ion exchange column chromatography and Sephacryl S-100 gel permeation column chromatography. Chemical composition and HPGPC analyses showed that the total sugar contents of the extracellular polysaccharides were more than 89% except mdz-1 and mdz-2. and the molecular weights of mdz-1, mdz-2, sh-11, sh-12 and sh-2 were 4.88 kDa,4.65 kDa.9.1 kDa. 2.21 kDa and 5.08 kDa, respectively. Monosaccharide compositions analysis by reversed-phase HPLC showed that the mdz-1 was mainly composed of Man with a small amounts of GlcN, Glc, Gal, Xly, Ara and Fuc, mdz-2 was mainly composed of Glc with small amounts of GlcN, Man, Gal, Ara and Fuc. sh-11 contained Ara with little of Glc and Gal, sh-12 contained Glc, Gal and Ara, sh-2 was mainly composed of Glc. The structural characterizations of sh-11, sh-12 and sh-2 were analyzed by IR and methylation analyses. The results showed that sh-11 consisted of Araf(1â†' â†'4)Arap(1â†', Galp(1â†' andâ†'4)Glcp(1â†' with the molar ratio of 1:2.9:1:1. sh-12 was composed of Glcp(1â†', â†'2)Arap(1â†',â†'2)Galp(1â†',â†'4)Galp(1-â†'4)Glcp(1â†',â†'4)Arap(1â†' and â†'3,4)Arap(1â†', sh-2 mainly consisted of â†'6)Glcp(1â†' with small amounts of Glcp(1â†', â†'2)Glcp(1â†' andâ†'2,6)Glcp(1â†'.The investigation provided novel marine extracellular polysaccharides for the "marine polysaccharides library", and laid material foundation for finding new marine medicinal polysaccharides from marine microorganisms. |
PDF Full Text Request