Studies on Exocellular Polysaccharides Prodused by some Cyanobacterial Species With Special Refrence to their Possible Applications

Abstract

Anabeana and Nostoc species are widely distributed in a large number of different habitats (soil, fresh water, symbiosis with higher plants or fungi) and in many cases they are characterized by the presence of external polysaccharidic investments; often released into the surroundings as water soluble polysaccharides (RPS). In this study, 22 cyanobacterial species were isolated, including 16 species of the heterocystous

Nostocales and 6 species of the non-heterocystous Oscillatorials, from from different habitats of soil and water and were screened for RPS production. The majority of the tested species were found to. release significant amounts of polysaccharides into the culture medium during photoautotrophic growth with different RPS daily productivities. This difference in RPS production between species do not seem to be linked to the original environment of the species since in the species described here, the slime was produced by both soil and water cyanobacteria with a comparable frequency. Regarding the RPS daily production of the tested spectes, the highest productivities were generally shown by species isolated from soils, suggesting that they need in their natural habitats to produce large amounts of mucilaginous material in order to create more favorable microenvironment (e.g. in order to trap the quantity of water necessary to ensure the proper functionality of cells or to chelate cations essentials to cell metabolism). The highest production ofRPS were obtained when the principal growth physiological parameters were at the optima for biomass production