Organic matter transformations during the weathering process of spent mushroom substrate

The weathering process of spent mushroom substrate (SMS) was studied to bet ter understand the chemical properties and transformations of organic matte r (OM) during the process. The SMS was piled (20 m by 6 m row of 1.5 m heig ht) in an open field and weathered during 15 mo. Chemical properties of the OM collected from the top and bottom parts of the weathering pile were stu died using C-13-nuclear magnetic resonance (NMR), tetramethylammonium hydro xide (TMAH) thermochemolysis-gas chromatograph/mass spectrometry (GC/MS), a nd pyrolgsis-gas chromatograph/mass spectrometry (Py-GC/MS). The C-13-NMR d ata suggested that weathered SMS from the top part of the pile degraded rap idly: the relative level of polysaccharides decreased by 33% while the leve l of aromatic C increased by 21% during the process. The TMAH thermochemoly sis chromatogram exhibited peaks of methylated derivatives of phenyl, guaia cyl and syringyl structures as well as some fatty acid methyl esters. Ligni n-derived products from TMAH thermochemolysis indicate that preferential de gradation of syringyl units and oxidation of C alpha-C beta bonds occurred in the SMS from the top part of the pile. In contrast, no major changes in lignin-derived structures were observed in the weathered SMS from the botto m part of the pile. The C-13-NMR, Py-GC/MS and TMAH thermochemolysis-GC/MS analyses indicated that the SMS decomposed rapidly at the top part of the w eathering pile, whereas decomposition at the bottom of the pile was signifi cantly slower, probably due to lack of oxygen. These analyses were shown to be useful techniques for the characterization of degradation processes in SMS. Therefore, their application to studies on OM transformation and humif ication processes is highly recommended.