Structural insights into polysaccharides in Ganoderma lucidum cell walls by solid-state NMR

Abstract

Ganoderma lucidum is a medicinal mushroom long esteemed in Asian traditional medicine for its health-promoting and longevity-enhancing properties. It contains over 400 bioactive compounds, among which its polysaccharides (GLPs) are especially significant due to their diverse biological functions. However, the molecular arrangement of GLPs within the cell-wall matrix remains poorly understood. To address this, we applied solid-state NMR for non-destructive structural characterization. Our analysis reveals a rigid core scaffold composed predominantly of β-1,3-glucan, chitin and chitosan, encased by a more mobile outer layer rich in β-1,4-glucan, α-1,3-glucans, α-1,4-glucan, arabinose, galactofuranose and α-mannose. Proton-driven spin-diffusion (PDSD) experiments identified 39 intermolecular contacts, especially between β-1,3-glucan and chitin, as well as among chitin chains. Within the core, chitosan displays nanosecond-to-microsecond mobility, suggesting a dynamically adaptable network. Hydration-kinetics measurements further distinguish these components, underscoring the hydrophilicity of β-1,3-glucan versus the hydrophobicity of chitin. Altogether, these findings support a model in which β-1,3-glucan–chitin interactions confer mechanical strength, while chitosan provides flexibility to enable adaptive cell-wall remodeling.