Investagation On The Exopolysaccharide From Marine Cyanothece Sp.113

Cyanothece sp. 113, producing a large amount of chlorophyll a and exopolysaccharide (EPS), which is a unicellular, aeorobic, diazotrophic and photosynthetic marine cyanobacterium, was isolated from sea. To develop a kind of applied EPS production strain, optimization of medium and cultivation conditions, structure analysis and Phylogenetic analysis were carried out in our Lab.The main results include:(1) The optimal medium for exopolysaccharide production by this cyanobacterial strain was 70.0g·l^-1 of added NaCl, 0 g·l^-1 of added NaNO₃, 0 g·l^-1 of added NaH₂PO₄ and 0.9 g·l^-1 oadded MgSO₄ on the basis of the modified F/2 medium for cultivation of marine algae. The optimal cultivation condition for exopolysaccharide production by this cyanobacterial strain were 29℃, aeration and continuous illumination with43×10² Lux. Under these optimal conditions, over 18.4 g ? l^-1 of exopolysaccharide was produced within 12 days. This was the highest exopolysaccharide yield produced by strains of Cyanothece obtained so far.(2)Effect of different aeration rates on cell growth and exopolysaccharide production by Cyanothece sp.113 were examined in 5-1 glass fermentor in this study. We found that the optimal aeration rate for exopolysaccharide production was 7.01mm^-1. Under this condition, 22.34gl^-1of exopolysaccharide from the fermentation medium with 11 days at 29℃ and continous illumination with 43×10² Lux was obtained. This was the highest yield of exopolysaccharide produced by marine cyanobacteria reported so far.(3)Hydrolyzed by pepsinum, protein, pigment and other small molecular impurity of the crude polysaccharides were removed by using Sevag reagent, H₂O₂ and dialysis against water, respectively. The polysaccharides were then precipitated by ethanol. No ultraviolet absorption signal of these polysaccharides was detected at 260 nm and 280...