Autoclave extraction applied to residual mushroom biomass: An efficient method for high-yield polysaccharide recovery

Mushroom-derived polysaccharides, particularly β-D-glucans, are valued for their biological activities and broad biotechnological applications. Although several conventional extraction methods have been established (cold-water, hot-water, and alkaline), the biomass that remains after exhaustive treatments is often discarded, despite its potential to retain valuable compounds. In this study, we evaluated whether residual laboratory materials from Pleurotus pulmonarius, Pholiota nameko, and Amanita muscaria still contain extractable polysaccharides by applying sequential autoclave extractions under aqueous, 5 % KOH, and 20 % KOH conditions. The extracts were precipitated with ethanol, quantified, and characterized by NMR, GC-MS, HPSEC-RI, and by total sugar and protein determinations. Significant yields were obtained, particularly with 5 % KOH, which produced up to 31.1 % in a single step, albeit with considerable protein content. Across extraction steps, a progressive decrease in molecular weight was observed, and monosaccharide analysis revealed that the extracts were composed predominantly of glucose. Structural characterization confirmed a predominance of β-D-glucans with (1→3)- and (1→6)-linkages, together with α-D-glucans with (1→3)- and (1→4)-linkages, as well as galactans and mannans. Overall, these findings demonstrate that autoclave extraction is a simple, efficient, and scalable approach to recover structurally diverse polysaccharides from mushroom residues, thereby enhancing resource utilization and opening new opportunities for fungal biomass valorization.