Chemical characterization and antioxidant activity of polysaccharide extract from spent mushroom substrate of Pleurotus eryngii

Abstract

Pleurotus eryngii has been widely cultivated in China and massive spent mushroom substrate (SMS) has been discarded. To utilize spent substrate of P. eryngii effectively, SMS was extracted by hot alkali liquor and a high yield (12.18%) of crude polysaccharide (designated as CPS) was obtained, then a polysaccharide-protein complex (RPS) was purified from CPS. Molecular characterization detected by size exclusion chromatography/multi-angle laser light scattering (SEC-MALLS) showed that the weight average molar mass (Mw) of RPS was 8.372×106g/mol. The molecular conformation of RPS was revealed to be a rigid rod form in aqueous solution. Monosaccharide composition analysis by GC–MS confirmed that RPS is a novel acid heteropolysaccharide and mainly composed of xylose, glucose, and arabinose. Then, FT-IR spectral analysis of RPS revealed prominent characteristic polysaccharide and protein groups. Pharmacological experiments in vitro suggested that both CPS and RPS exhibited strong antioxidant activities in a dose dependent manner, using different in vitro models like ABTS, superoxide, hydroxyl and DPPH. The high-yield crude polysaccharide showed potential for application as strong antioxidant in food industry. The study provided a reliable approach for spent resource recovery, which would be significant to sustainable development of mushroom industry and environmental protection.