Chemical nature and composition of compost during mushroom growth

Improvement of the process of mushroom composting is of importance in order to provide an optimal growing medium needed for the mushroom. Since compos ting produces a food source for the mushroom, the compositional changes of mushroom compost occurring during the growth cycle of the button mushroom, Agaricus bisporus, were studied. Samples were collected during spawning, ca sing and the following four flushes. Samples were analyzed for their elemen tal composition, carbohydrates, FTIR, C-13-NMR, pyrolysis-GC/MS and tetrame thylammonium hydroxide (TMAH) thermochemolysis-GC/MS. The carbohydrate anal ysis revealed a decrease in the total amount of about 40% of the identified monosaccharides during mushroom growth. The C-13-NMR data also confirm tha t polysaccharides are the main fraction degraded (or utilized by the mushro oms) during the cropping period. These findings were also confirmed by chan ges in the absorbance of functional groups observed in the FTIR spectra. Py rolysis data revealed chromatographic peaks related to polysaccharides-, pr oteins- and lignin-derived compounds. Both pyrolysis and TMAH thermochemoly sis data show degradation of Lignin structures during the growth period. Li gnin alteration primarily involved a preferential degradation of syringyl u nits and oxidation of side chains of guaiacyl moieties. This study suggests that the polysaccharide fraction of the mushroom substrate is the main org anic fraction utilized during the process. In addition, alterations of lign in structures have occurred although its relative content usually increases during mushroom cropping.