Di-n-butyl phthalate stress induces changes in the core bacterial community associated with nitrogen conversion during agricultural waste composting

Nitrogen (N) loss during composting reduces the quality of compost products and causes secondary environmental pollution. Phthalate esters (PAEs) are common pollutants in agricultural wastes. However, little information is currently available on how PAEs affect N conversion during agricultural waste composting. This research systematically analyzed the impact of di-n-butyl phthalate (DBP) pollution on the N conversion and its related microbial community during composting. Our results indicated that DBP stress results in a shorter thermophilic phase, and then slower compost maturation during composting. Notably, DBP stress inhibited the conversion of ammonia to nitrate, but increased the release of NH₃ and N₂O leading to an increased N loss and an elevated greenhouse effect. Furthermore, DBP exposure led to a reduction of bacteria related to NH₄⁺ and NO₃⁻ conversion and altered the network complexity of the bacterial community involved in N conversion. It also reduced the abundance of a major nitrification gene (amoA) (P < 0.01) and increased the abundance of denitrification genes (nirK and norB) (P < 0.05). Moreover, DBP affected the overall microbial community composition at all tested concentrations. These findings provide theoretical and methodological basis for improving the quality of PAE-contaminated agricultural waste compost products and reducing secondary environmental pollution.