Chemical composition and production of exopolysaccharides from representative members of heterocystous and non-heterocystous cyanobacteria

Abstract

Exopolysaccharide (EPS) production and chemical composition of heterocystous and non-heterocystous cyanobacteria of subgroups 3, 4, and 5 together with four new species isolated from Pantelleria (Italy) hard sands and from a lake in the proximity of Edmonson Point in Antarctica were studied. The yield of extracellular soluble polysaccharides (RPS) and slime layers (CPS) showed a significant variation from one strain to another; generally RPS were more abundant than CPS with the exception of Anabaena torulosa and Scytonema hoffmanni. Phormidium sp. was the best producer of EPS. Among heterocystous cyanobacteria belonging to Nostocaceae the new species Anabaena WSAF and A. torulosa were found to produce the highest level of EPS. Among heterocystous cyanobacteria other than Nostocaceae, the best producer of EPS was Chlorogloeopsis sp. 6912. Four species were chosen for studying the effects of growth conditions, nutritional, physical and chemical, on total EPS formed. Glucose and galactose were the neutral sugars widely present in the species examined, although other sugars such as mannose and xylose were plentiful in some species. Amino-sugar, as glucosamine, and uronic acids were also found in EPS of some cyanobacteria. Finally the inhibition of avarol, a sesquiterpene hydroquinone, toxicity on Artemia salina by EPS of some species was analysed.