Aeribacillus pallidus inoculant orchestrates functional microbial succession for enhanced nitrogen transformation in high-protein waste composting

The valorization of protein-rich meat and bone meal (MBM) via composting is hampered by significant nitrogen loss. Genomic analysis of Aeribacillus pallidus (A. pallidus) strain 60 revealed a genetic repertoire encoding potent proteolysis and nitrogen assimilation. We hypothesized that this strain could function as a microbial catalyst to redirect nitrogen flux during MBM composting. In a laboratory-scale trial, inoculation with A. pallidus triggered a rapid thermal surge (reaching 70 °C) and proteolytic cascade, significantly accelerating maturation. Crucially, this process enhanced relative nitrogen retention, increasing final total Kjeldahl nitrogen (TKN) concentration by 10.87–13.33% and nitrate by 13.75–18.65% compared to controls. Physicochemical and microbial profiling revealed that these improvements were driven by an inoculant-induced environmental modification rather than sustained inoculant dominance. The created thermal niche facilitated a distinct two-stage succession: an initial enrichment of proteolytic genera (Thermoactinomyces, Ammoniibacillus) followed by the establishment of a putative nitrifying community dominated by Pseudoxanthomonas. This study illustrates how a pioneer inoculant can drive functional microbiome assembly through niche modulation, providing a targeted strategy for optimizing nitrogen recovery in protein-dense waste valorization.