Confirming the key factors influencing the biosynthesis and regulation of organic nitrogen in composting

Organic nitrogen (ON) possesses the ability to sustain a stable nitrogen supply fertility during composting. However, research on the biosynthesis and regulation of ON remains limited. The results indicated that despite variations in microbial communities between the chicken manure composting (T group) and kitchen waste digestate composting (F group), their functional genes were remarkably similar, and the microorganisms exhibited similar functions. The microbial community structure of T group was more complex than that of F group. Network analysis identified Saccharomonospora, Corynebacterium, and Thermobifida as the core microorganisms in T group, whereas Oceanobacillus, Staphylococcus, and Fictibacillus were predominant in F group. These microorganisms play a role in the biosynthesis and regulation of various forms of ON (including amino acid nitrogen (AAN), amino sugar nitrogen (ASN), amide nitrogen (AN) and hydrolyzable unknown nitrogen (HUN)) and may contribute to differences in ON production due to the distinct nature of the materials. The core functional genes of the two groups of materials were determined by random forest model. Although differences in functional genes were present between F group and T group, the most crucial genes for ON biosynthesis in both groups were those with ammonia assimilation (such as glnE, gltB, gltD, etc.). The nitrogen transformation processes associated with these core genes can be modulated by managing the activity of multifunctional microorganisms, particularly through the control of ammonia assimilation, nitrate reduction, and ammonification, which are related to NH₄⁺ levels. Notably, electric conductivity (EC), temperature (Tem.), pH, and NH₄⁺ were the pivotal environmental factors influencing the biosynthesis of ON. This investigation enhances our understanding of the previously underexplored mechanisms of ON biosynthesis and regulation.