Ammonia assimilation is key for the preservation of nitrogen during industrial-scale composting of chicken manure.

Nitrogen loss from compost is a serious concern, causing severe environmental pollution. The NH4+-N content reflects the release of NH3. However, the nitrogen conversion pathway that has the greatest impact on NH4+-N content is still unclear. This study attempted to explore the key pathways, core functional microorganisms, and mechanisms involved in the transformation of ammonia nitrogen during composting. KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathways revealed that ammonia assimilation was dominated by the glutamate dehydrogenase (GDH) pathway (53.4%), which is crucial for nitrogen preservation. The combined analysis of KEGG, NR species annotation, and co-occurrence network identified 20 easy-to-regulate obligate core nitrogen-transforming functional microorganisms, including 18 ammonia-assimilating bacteria. Furthermore, the effects of environmental parameters on the obligate core functional microorganisms were investigated. The present study results provided a theoretical basis for the utilization of ten ammonia-assimilating bacteria, such as Paenibacillus, Erysipelatoclostridium, and Defluviimonas to improve the quality of compost.