Partial characterization of extracellular polysaccharides from cyanobacteria

Area of Science:

• Microbiology
• Biochemistry
• Polymer Science

Background:

• Cyanobacteria produce extracellular polysaccharides (EPS) with diverse potential applications.
• Understanding the physico-chemical properties of EPS is crucial for optimizing their use.

Purpose of the Study:

• To perform a physico-chemical characterization of EPS from four cyanobacterial strains.
• To analyze sugar composition, functional groups, thermal stability, and rheological behavior of EPS.

Main Methods:

• Physico-chemical characterization of EPS.
• Sugar composition analysis via hydrolysis.
• Infrared (IR) spectroscopy for functional group identification.
• Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal stability.
• Viscosity measurements in NaCl solutions.

Main Results:

• EPS composition varied, including mannose, glucose, xylose, and ribose.
• IR spectra indicated O-H, C-H stretching, and C-H bending vibrations; specific peaks suggested sulfur-containing groups in Cyanothece sp. EPS.
• High thermal stability was confirmed, with polysaccharides stable up to approximately 250°C.
• Intrinsic viscosity of Oscillatoria sp. and Nostoc sp. EPS decreased 1.6-fold in 0.1 M NaCl, while commercial guar and xanthan gum showed 3-5 fold reductions.

Conclusions:

• Cyanobacterial EPS exhibit distinct physico-chemical properties, including thermal stability and salt-induced viscosity changes.
• The characterized EPS possess properties potentially useful in various industrial applications.
• Further research can explore the specific functionalities and applications of these microbial polysaccharides.