Study on the dynamic changes of physicochemical properties, nitrogen functional genes, bacterial communities and their interactions during the composting of Chinese medicinal herbal residues

Abstract

Aerobic composting of Chinese medicinal herbal residues (CMHRs) constitutes an efficacious waste management strategy, yet optimizing nitrogen content remains challenging. The variations of physicochemical properties, nitrogen functional genes, and bacterial communities throughout the composting process, along with their interrelationships were explored in this study. The final compost product achieved maturity, with a C/N ratio of 10.96 and a nitrification index of 0.19. Quantitative PCR analysis indicated suboptimal nitrification efficiency due to insufficient activity of nitrifying microorganisms. 52 biomarkers at four stages of composting were identified by linear discriminant analysis effect size. Functional annotation of prokaryotic taxa exposed chemoheterotrophy (17.05%–25.52%) and aerobic chemoheterotrophy (11.84%–22.65%) as dominant bacterial functions. Canonical correspondence analysis discovered total nitrogen exerted the most significant impact on bacterial genus distribution. Bacteria affectting nitrification genes and nitration products, especially Anseongella and Weissella, were spotted through network analysis. The results revealed the important microbial groups facilitating the nitrogen conversion of compost of CMHRs, which provided a basis for optimizing nitrogen retention and improving the quality of compost.