Extraction, purification and antibacterial activities of a polysaccharide from spent mushroom substrate

To contribute towards effective exploitation and utilization of spent mushroom substrate (SMS), a water-soluble polysaccharide named PL was isolated and purified from SMS. The total sugar content and monosaccharide composition were analyzed by phenol–sulfuric acid method and capillary electrophoresis, and infrared spectroscopy was also performed for structure characterization. The results showed that the total sugar content of crude polysaccharide from SMS was about 25.8%, the polysaccharide contained two fractions (PL1 and PL2), which was mainly composed of glucose, rhamnose and mannose with a molar ratio of 1:3.13:1.16. The attributions of the main absorptions of both PL1 and PL2 were characteristic of glycosidic structures, and the FT-IR spectra of PL2 and lentinan were very similar. Escherichia coli, Staphylococcus aureus and Sarcina lutea were used to study the antibacterial activity and minimal inhibitory concentrations (MICs) of the polysaccharide. The antibacterial activity of polysaccharide from SMS against E. coli was the strongest, while the weakest against S. lutea, and the MICs of PL2 were 12.5, 25 and 100 μg/mL, respectively.