Extraction, characterization and antioxidant activity of polysaccharides of spent mushroom compost of Ganoderma lucidum

To contribute toward effective exploitation and utilization of spent mushroom compost (SMC) of Ganoderma lucidum (SMC-G), a water-soluble polysaccharide of GPS was extracted, and then two fractions (GPS-1 and GPS-2) were purified from SMC-G. The optimum conditions for GPS extraction were optimized by the central composite design (CCD) and the GPS yield reached 3.84% at a ratio of water to material of 34.5, a precipitation time of 19.82 h, and pH of 7.88. Characteristic analysis showed that GPS-1 and GPS-2 were heteropolysaccharides, and had glycosidic structures (OH, CH, CO and COC). Both GPS and its fractions showed potential antioxidant activities by scavenging hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, and increasing the reducing power in vitro; and by improving the CAT activities, and lowing the LPO and MDA contents in vivo, respectively. The results provided a reference for the exploitation of SMC-G which would be significant to sustainable development of industry and agriculture, environmental protection and full utilization of resources.