Abstract The substrate production process for the edible mushroom Agaricus bisporus offers a controlled model environment to investigate organic matter transformation. Despite the central role of humic substances (HS) in organic matter dynamics, detailed insights into their compositional changes during decomposition are limited. We investigated the formation and transformation of dissolved and solid phase HS during microbial composting and subsequent mycelial growth of A. bisporus . Total carbon and nitrogen were analyzed in both bulk material and HS fractions. Additionally, bulk material was analyzed for carbohydrates, fatty acids, and lignin content and composition. Pyrolysis–GC–MS was used to characterize humic acids (HA), fulvic acids (FA), and the bulk material. Throughout microbial composting HS formed, with HA as main fraction followed by FA. The formation of HS coincided with substantial degradation of cellulosic components and enrichment of organic nitrogen. HA was particularly enriched in lignin(derived) and nitrogen-containing compounds. During early mycelial growth of A. bisporus HS and particularly HA decreased, thus HS are an accessible source of carbon and nitrogen for fungal metabolism.
Duran et al. (Fri,) studied this question.