Partial characterization of cyanobacterial extracellular polymeric substances for aquatic ecosystems

Eutrophication, which causes cyanobacterial blooms, is a worldwide concern leading to further deterioration in water quality and adverse changes in the ecosystems due to oxygen consumption of decomposing cell masses. The investigation of extracellular polymeric substances (EPSs) contributes to a better understanding of the growth and proliferation of cyanobacteria. It could be a key to prevent bloom formation of toxic cyanobacteria which can be hazardous for human and animals, especially those in aquatic environments. Hence, the characterization of cyanobacterial EPS has become an important issue to obtain a better understanding of the formation of EPS. In this study, an attenuated total reflectance-Fourier transform infrared, proton nuclear magnetic resonance (H-NMR) and high-resolution Raman spectroscopic methods were used to identify functional groups of EPS obtained from Arthrospira maxima. Thermogravimetric analysis (TGA) was also applied to characterize thermal-stability and structural properties of the EPS. Thermal stability was attributed to the complex and heterogeneous molecular structure of EPS including uronic acid and calcite crystal since 34% of the EPS residue remained after TGA. The presence of uronic acid and calcite crystal causes an overall negative charge and acidic property to the EPS which is of biotechnological importance. Protein amount of EPS was calculated as 7.12% by Bradford assay.