Metabolomics analysis of advancing humification mechanism in secondary fermentation of composting by fungal bioaugmentation

The aim of this study was to investigate the differential metabolites and core metabolic pathways caused by fungal bioaugmentation (pH regulation and Phanerochaete chrysosporium inoculation) in secondary fermentation of composting, as well as their roles in advancing humification mechanism. Metabolomics analyses showed that inoculation strengthened the expression of carbohydrate, amino acid, and aromatic metabolites, and pH regulation resulted in the up-regulation of the phosphotransferase system and its downstream carbohydrate metabolic pathways, inhibiting Toluene degradation and driving biosynthesis of aromatic amino acids via the Shikimate pathway. Partial least squares path model suggested that lignocellulose degradation, precursors especially amino acids and their metabolism process enhanced by the regulation of pH and Phanerochaete were the main direct factors for humic acid formation in composting. This finding helps to understand the regulating mechanism of fungal bioaugmentation to improve the maturity of agricultural waste composting. [Display omitted] •P. Chrysosporium inoculation promoted carbohydrate, glycine, aromatic metabolites.•Reducing pH stimulated PTS, carbohydrate translocation and metabolism in composts.•Inoculation with reduced pH promoted aromatic amino acid synthesis by Shikimate way.•Lignocellulose, precursors, and amino acid metabolism mainly drove humus formation.