Characterization of Fungal-Degraded Lime Wood by X-Ray Diffraction and Cross-Polarization Magic-Angle-Spinning ¹³C-Nuclear Magnetic Resonance Spectroscopy

Abstract

X-ray diffraction, scanning electron microscopy (SEM), and solid-state cross-polarization magic-angle-spinning (CP/MAS) (13)C-NMR spectroscopy were applied to determine changes over time in the morphology and crystallinity of lime wood (Tilia cordata Miller) generated by the soft-rot fungi. Wood samples were inoculated with Trichoderma viride Pers for various durations up to 84 days. Structural and morphological modifications were assessed by comparing the structural features of decayed lime wood samples with references. Significant morphology changes such as defibration or small cavities were clearly observed on the SEM micrographs of lime wood samples exposed to fungi. Following the deconvolution process of the diffraction patterns, the degree of crystallinity, apparent lateral crystallite size, the proportion of crystallite interior chains, and the cellulose fraction have been determined. It was found that all crystallographic data vary with the duration of exposure to fungi. The degree of crystallinity and cellulose fraction tend to decrease, whereas the apparent lateral crystallite size and the proportion of crystallite interior chains increase with prolonged biodegradation processes. The most relevant signals in CP/MAS (13)C-NMR spectra were assigned according to literature data. The differences observed were discussed in terms of lignin and cellulose composition: by fixing the lignin reference signal intensity, the cellulose and hemicelluloses moieties showed a relative decrease compared to the lignin signals in decayed wood.

How spectroscopy and microspectroscopy of degraded wood contribute to understand fungal wood decay

“…Other methods to visualise and accentuate the spectral information are deconvolution of overlapping bands, a method most frequently applied to 13 C CPMAS NMR spectra (Popescu et al 2010a), calculation of difference spectra and second derivatives, or two-dimensional correlation spectra, which was in the context of fungal wood degradation applied for NMR spectra (Yelle et al 2008; Yelle et al 2011) and for IR spectra (Popescu et al 2010b). …”

“…Popescu et al (2010a) reported the apparent increase of crystallite size in lime ( Tilia cordata ) wood degraded by Trichoderma viride —a wood-inhabiting deuteromycete—and assigned this effect to higher mobility of less ordered polysaccharide chains after selective degradation of amorphous polysaccharides. The authors investigated the same degraded wood with 2D-correlation FT-MIR spectroscopy and found decreased carbohydrate content and decreased crystallinity.…”

Chemical Characterization of Waterlogged Charred Wood: The Case of a Medieval Shipwreck

“…However, CrI values were not in accordance with the respective crystallite sizes (L), as for the uncharred material, L presented the lowest value. The considerably high CrI of uncharred material was not anticipated, as in archaeological wood the crystallinity usually decreases with decay [23,[47][48][49]. Nonetheless, crystallinity's increase has been reported by other authors in initial stages of degradation due to the dramatic loss of amorphous cellulose regions [23,48,50].…”

Benzylation and Characterization of Cold Naoh/Urea Pre-Swelled Bamboo

“…3. The signals that correspond to cellulose were observed at 63 ppm (C6), 75 ppm (C2, C3, and C5), 83, 87 ppm (C4), and 104 ppm (C1) (Popescu et al 2010). It has been reported that xylans have signals at 102 ppm (C1), 84 ppm (C4), 72 to 75 ppm (C2 and C3), and 65 ppm (C5) (Wallace et al 1995); however, these signals were overlapped with the strong signals of cellulose.…”