BIOLOGICAL ACTIVITY AND STRUCTURAL CHARACTERIZATION OF A NOVEL EXOPOLYSACCHARIDE ISOLATED FROM A FOREST FUNGUS IN NORTH OF IRAN

Background and Aim:Fungal exopolysaccharides (EPSs) have been recognized as high value biomacromolecules with strong bioactivity. In the present study, a fungal strain, designated SF1344, producing a high level of extracellular biopolymer was isolated from forest area of Golestan province, North of Iran.Methods:The biopolymer was purified by the sequential precipitation via solvent extraction. Paper chromatographic analysis (TLC) and FT-IR spectrum were used to structural analysis of the EPS. GC-MS along with derivizataion procedure was applied for complementary characterization. Antioxidant and antimicrobial activity were evaluated base on DPPH and MIC method, respectively.Results:Structural analysis of the growth-dependence EPS (2.73 g/l ± 0.02), revealed the presence of hydroxyl, carboxyl, N-acetyl and amine groups. analysis of the methylated EPS showed the presence of D-glucose, D-xylofuranose and D-galactofuranose with approximate mass-to-charge-ratio of m/z 405, 475 and 441, respectively, based on GC-MS library compared to the standard sugars treated with the same reactions. Antioxidant activity based on DPPH method, suggested that EPS from SF1344, strongly scavenged radicals about (80.6%) compare to ascorbic acid (0.5 mM) as the positive control. Antimicrobial activity of the EPS was highlighted by disc diffusion (diameter of inhibition zone) and broth micro-dilution method (minimum inhibitory concentration). The best activity against S. typhimurium ATTC (14023), S. paratyphi A ATCC (1230) and S. aureus ATCC (25022) with MIC of 100 µg/ml, 50-100 µg/ml and 50-100 µg/ml, respectively, was provided by biopolymer obtained from SF1344.Conclusion:The fungal EPS with unique structural composition exhibited strong invitro bioactivity which is powerful resources of medicinal applications.

Keywords:

Antioxidant , Antimicrobial , Biopolymer , GC-MS , minimum inhibitory concentration (MIC)