Lignocellulose biodegradation to humic substances in cow manure-straw composting: Characterization of dissolved organic matter and microbial community succession.

Composting, a sustainable practice, facilitates the biodegradation of organic waste, notably lignocellulosic biomass, into value-added humic substances. Despite its potential, the application of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to characterize dissolved organic matter (DOM) for assessing the changes in maturity during cow manure-straw composting is underexplored. Furthermore, the link between these changes, microbial community succession, and the biochemical pathways of humus formation is seldom investigated. This study leveraged ESI FT-ICR MS and metagenomic analysis to elucidate the molecular changes in DOM, identified key microbes in humus formation, and traced the humus formation pathway during composting. The results highlighted the crucial role of microorganisms such as Thermobifida, Luteimonas, Ascomycota, and Chloroflexi in accelerating the breakdown and transformation of plant biopolymers. Large molecular nitrogen compounds from cow manure-straw were converted into unsaturated, aromatic oxygen compounds, which resemble humic substances in their chemical properties. The ESI FT-ICR MS data revealed that humus formation occurred through a series of reactions, including protein deamination, lignin delignification, and decarbonylation. This research offered new light on strategies to enhance the stabilization and humification of cow manure-straw composting, contributing to more effective composting processes.