Combined analysis of microbial community and microbial metabolites based on untargeted metabolomics during pig manure composting

Compost has been widely used in agriculture in recent years, but the nutrients it provides are far from enough for plant growth. Therefore, it is necessary to systematically explore the fermentation process of composting. In this study, the succession of microbial community and metabolite characteristics in compost were analyzed by using microbial sequencing and metabolomics techniques. The results showed that compared with mesophilic phase and cooling phase, the richness and diversity of bacterial community decreased in thermophilic phase. At the genus level, Pseudomonas (8.90%), Lactobacillus (3.99%), Bacteroidetes (3.39%), Flavobacterium (3.25%) and Prevotella (Prevotella_9, 2.33%, Prevotellaceae_NK3B31_group, 2.44%) were the dominant genera in the pig manure composting. The abundance of Pseudomonas and Flavobacterium increased significantly while Lactobacillus and Prevotella were significantly decreased after composting, and the abundance of Bacteroidetes increased first and then decreased. Fatty acyls, sterol lipids, glycerophospholipids, polyketides and prenol lipids were common microbial metabolites in compost. Moreover, the linoleic acid metabolic pathway was significantly enriched in the three stages of composting, and linoleic acid metabolism might be the primary function of the microbial community in composting. The network analysis showed that between the microbial communities or between the microbial community and metabolites were closely related to each other.