Microbial community and function in nitrogen transformation of ectopic fermentation bed system for pig manure composting

In this work, agricultural wastes were treated by composting in an ectopic fermentation bed system (EFBS) with a continuous nitrogen addition technique. With decreasing of NH4+-N concentration and increasing of NO3−-N concentration were observed, and activities of protease, urease and nitrate reductase changed significantly during the fermentation process. To elucidate the key microbes and their function in nitrogen-transforming, microbial diversity and clusters of orthologous groups (COGs) in composting materials were evaluated using metagenomic technology. Comparing with ammonification, the COGs involved in nitrification and denitrification were predominant in the composts. The correlation heatmap revealed that Streptomyces predominant in ammonification was significantly affected by contents of N, NH4+-N and NO3−-N. Meanwhile, ammonia-oxidizing archaea (AOA) had a positive relationship with moisture. The most abundant genera in denitrification had positive relationships with N and NO3−-N. The results indicated that EFBS had functionally diverse microbes and COGs for NH3 removal.