Evaluation of Antioxidant and Antibacterial Activities of the Polysaccharides from Mycelium and the Culture Medium of Pleurotus Eryngii Strain UN-1

Pleurotus eryngii was one of the most precious and ordinary edible mushrooms, and its polysaccharides were the major active substances. In this study, P. eryngii strain UN-1 was cultured in a liquid medium at 25℃ under a shaking of 80 rpm for 7 days. Two crude polysaccharides named CPN and CPNM were obtained from the mycelium of P. eryngii UN-1 and its broth culture medium, respectively. After partial purification by cellulose DEAE-52 column chromatography and Sephadex G-100 gel-filtration, two fractions (PNP-1 and PNP-2) from CPN and one (PNMP-1) from CPNM were eluted and subjected to physicochemical properties, antioxidant, and antibacterial activities, in addition, the crude polysaccharides. The in vitro antioxidant assay revealed that all samples showed moderate scavenging capacities on DPPH radical (6.31-80.92%), ABTS radical (9.33-67.26%), and hydroxyl radical (11.21-79.53%) at different concentrations (0-2000 μg/mL), and PNP-2 exhibited the highest scavenging activity for all tested free radicals. Moreover, the antibacterial activity of the most active fraction (PNP-2) showed a significant effect against Escherichia coli, Bacillus Subtillis, Salmonella enterica, and Staphylococcus aureus subsp. Aureus strains with Minimum Inhibitory Concentration (MIC) values (2.5, 5, 2.5 and 5 mg/mL, respectively). Notably, the UV-vis Spectrophotometer confirmed that multiple active known compounds such as uremic acid were detected in all tested fractions, which confirmed the antioxidant and antimicrobial activities obtained in this study. Conclusively, the polysaccharides obtained from P. eryngii UN-1 have the potential to act as a functional food ingredient or a preventive drug against human pathogenic bacteria.