Biochar and manganese dioxide regulate nitrogen transformation via quorum sensing of core microbiota in compost

Improving the efficiency of element cycling and elucidating its microbiological mechanisms in aerobic composting is crucial for utilizing industrial and agricultural waste as a resource. This study aimed to analyze and compare the effects of two conditioners, biochar and manganese dioxide (MnO 2 ), on inorganic nitrogen transformation in the aerobic composting process of a mixture of flax retting liquor (FRW), straw, and chicken manure from the perspective of quorum sensing signaling molecules and two-component system (QSM-TCS). The results indicated that during the aerobic composting of a mixture of corn straw and chicken manure, the addition of FRW resulted in a 39.2 ​% increase in total nitrogen content. Additionally, adding conditioners, such as biochar and MnO 2 , continuously enhanced nitrogen transformation. Furthermore, biochar reduced NH 4 + -N loss by 32.26 ​%, and MnO 2 decreased NO 3 − -N loss by 2.10 ​%. Biochar improved temperature perception in core operational taxonomic units, promoting genera such as Ornithinicoccus and Thermobifida , and thereby enabling them to better use the luxQ - luxN , rpfC - rpfG , and qseC - qseF gene pathways to accelerate NH 4 + -N accumulation. In contrast, MnO 2 enhanced microbial adaptation to pH changes, increasing pH tolerance in bacteria such as Enterococcus and Bacillus , which stimulated genes involved in nitrification and anaerobic ammonium oxidation. This facilitated complementary effects in the QSM-TCS system, thereby stabilizing NO 3 − -N retention. The findings highlighted the critical role of microbial-driven inorganic nitrogen transformation pathways, offering insights into the optimization of aerobic composting systems for sustainable agriculture and environmental protection. • Biochar reduced NH 4 + -N loss rate and MnO 2 conserved NO 3 − -N during FRW composting. • Biochar enhanced temperature perception; MnO 2 improved pH adaptation. • Biochar and MnO 2 enriched different key genera during flax retting liquid composting. • MnO 2 complemented comDE and comAP for nitrification-anammox.