Cultivation of Fomitopsis betulina fruiting bodies on alternative substrates: Uncovering the metabolomics profiling by HR-MAS NMR and FTIR spectroscopies

Fomitopsis betulina fruiting bodies, which are edible when young, were cultivated on four lignocellulosic substrates: birch ( Betula alba , natural host, control), smoke tree ( Cotinus coggygria ), black alder ( Alnus glutinosa ), and hazelnut shells ( Corylus avellana ). To study the impact of substrate and developmental stage on chemical composition, samples were evaluated using FTIR spectroscopy to assess macromolecular features, HR-MAS 1 H NMR spectroscopy to profile low-molecular-weight metabolites, and multivariate statistical methods (PCA, SIMCA, OPLS-DA, and OPLS-HDA). Morphological classification was confirmed by chemometric analysis: young fruiting bodies were enriched in free sugars and β -glucan fragments, whereas mature specimens contained more chitin-derived oligomers, esters, and amide signals. These results demonstrate that substrate selection influences both amino acid and carbohydrate profiles, while maturation is associated with a shift from soluble sugars toward structural polysaccharides. From a practical perspective, harvesting at the early developmental stage favors the accumulation of free sugars and β -glucan fragments, whereas substrate selection can be optimized to enhance the nutritional, sensory, and technological properties of F. betulina .