Metagenomics Analysis of the Impact of Protein-Degrading Functional Microbial Agents on Composting of Chicken Manure from Cereal Hulls

Abstract

In this study, four highly efficient protein-degrading bacteria (Siccibactercolletis, Bacillus thuringiensis, Bacillus cereus, and Bacillus sp. (in: Firmicutes)) were screened from soil and fermentation beds and prepared into a mixed microbial agent in a ratio of 1:1:1:1. The effects of inoculation with protein-degrading functional bacteria on nitrogen transformation rate, microbial community, and functional genes during chicken manure–rice husk composting were studied. With the addition of functional agents, the nitrogen loss in chicken manure composting was reduced to 17.05%, and ammonia emissions were also reduced. Firmicutes, Proteobacteria, Bacteroidetes, Cocci, and Actinobacteria became the dominant bacterial communities, accounting for 85.41%~98.52% of the overall bacterial community in the compost; it promoted the growth of microorganisms such as Pseudogracilibacillus and Lachnospiraceae in the compost. Metagenomic analysis revealed that the addition of functional bacterial agents enhanced the expression of nitrogen fixation genes (nifK, nifH, and glnA) during the high-temperature phase, increased the diversity of bacteria associated with the nitrogen cycle in the compost, and improved the absorption and fixation of nitrogen source elements by microorganisms. Additionally, it strengthened the correlation between microbial communities, the composting environment, and functional genes. This study provides a theoretical basis for the efficient application of microbial agents and the reduction of pollution in chicken manure hull composting.