Anticoagulant and antibacterial activities of polysaccharides fraction from Nostoc muscorum and Arthrospira platensis cultivated under abiotic stress conditions

Background
Cyanobacteria are very old phylogenetic group of prokaryotic phototrophic microorganisms. With repeated quick adaptations to different environmental circumstances in different ecosystems, their presence in the biosphere from the early Precambrian and extensive diversity up to the present witness to with their amazing and continuous physiologically and environmentally important life strategies.
Objective
The aim of this study was selected Nostoc muscorum and Arthrospira platensis as cyanobacteria species for studying the effect of some abiotic stress conditions (light intensity & sulfate concentrations and aeration rate) on polysaccharide production (intracellular and extracellular). Evaluate the ability of the different algal extracts as anticoagulants and antibacterial.
Materials and methods
N. muscorum was cultivated on BG-11 medium and A. platensis was cultivated on Zarrouk medium. Algal species were grown and incubated in controlled photoperiod of, 16-8 l/D cycles, light intensity of 40 µE/m /s and temperature at 25°C±2°C with continuous aeration supplied with air (60 bubbles/min.). Cultivation of algae under abiotic stress conditions and the growth rate of both investigated species was determined by optical density and dry cell weight. Extraction of polysaccharides by different methods and determination of total hydrolysable carbohydrates. Determination of sulfate contents. Protein molecular weight determination in algal species were determined by SDS-page. Determination of bacterial activity of different algal extracts, was tested in vitro against G and G bacterial strains using the filter paper disk diffusion method, The Gram-positive bacterial strains, Staphylococcus aureus and the gram-negative strains, Pseudomonas aeruginosa, Also the anticoagulating activity of promising algal extracts was investigated using the method of US pharmacopeia.
Results and conclusion
There was positive correlation between light intensity, MgSO concentrations and aeration, on algal growth and polysaccharide production. Ethanol was found to be highly efficient for polysaccharide extraction. Intracellular polysaccharide content was higher than extracellularly released one in both the studied cyanobacteria species. Intracellular polysaccharides of A. platensis exhibited antibacterial activity higher than those of N. muscorum. Anticoagulation efficiency of sulfated polysaccharides in both investigated stressed cyanobacteria species was highly pronounced (>30 min). Chemically active groups showed by FT-IR of the produced polysaccharides under stressed conditions are variable depending on both the type of stress and the method of extraction.