Molecular mechanisms of dissolved organic matter transformation and microbial interactions in composting

Industrial composting of food waste digestate (FW) and chicken manure (CM) involves distinct dissolved organic matter (DOM) transformation pathways and different microbial interaction mechanisms. This study used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and shotgun metagenomics (for microbial community profiling) to compare interactions between DOM and microbial communities in the two composting processes. Results show that FW is dominated by labile organic matter (OM). This dominance increases the degree of DOM oxidation and the relative abundance of CHO. This labile carbon environment selected for a simplified microbial community dominated by key genera, yet facilitated active potential molecular transformations (PMTs) of DOM. These PMTs were characterized by an increase in thermodynamically limited processes (TLPs), indicating a carbon source-oriented pathway. In contrast, PMTs of DOM in CM favor thermodynamically favorable processes (TFPs), exhibiting higher aromaticity and CHOS abundance. The microbial community remains highly diverse, strongly connected, and functionally complementary, forming a synergistic network that supports coupled nitrogen-sulfur transformations. Environmental factors differentially regulate the two systems. This study indicates that the initial chemical properties of the composting feedstock fundamentally shape the PMTs of DOM pathways and the microbial communities they drive, providing an important theoretical basis for optimizing organic solid waste resource recovery processes.