Examination of the chemical changes in spruce wood degraded by brown-rot fungi using FT-IR and FT-Raman spectroscopy

•The SEM images clearly showed that how the fungal hyphae spread in the cell lumens.•FT-IR analysis elucidated polysaccharide degradation with increasing time.•FT-Raman analysis powerfully revealed changes in the lignin.•The extensive degradation changes the carbohydrate/lignin ratio.

Spruce sapwood was subjected to brown rot fungi (Coniophora puteana) for up to 80 days to study the degradation of the cell wall. The chemical composition of spruce sapwood that was modified by brown-rot fungi causing mass losses up to 60.99% was examined using Fourier transform infrared (FT-IR) and FT-Raman spectroscopy. During the first stage of brown rot, no changes were observed using light microscopy but electron microscopy clearly showed how the cell lumens were occupied by fungal hyphae. FT-IR and FT-Raman results revealed that carbohydrate peaks simultaneously diminished or disappeared with mass loss as decay proceeded. However, as the decay proceeded and the wood polysaccharides depolymerized, the intensity of peaks corresponding to lignin increased. However, the lignin content maintains relatively constant.