Efficient Conversion of Mushroom and Sawdust Residues in Protaetia brevitarsis Biosystem: Characterization of Humic Acid and Bacterial Communities.

The accumulation of agricultural residues presents an environmental challenge. PBLs have emerged as effective agents for biodegrading such biomass, producing frass rich in HA with low phytotoxicity, positioning it as a potential biofertilizer. However, the influence of PBL bioconversion on HA yields and microbial communities across different substrates remains underexplored. In this research, PBL is fed on two Pleurotus SMSs and oak sawdust. The resulting frass was characterized and showed low phytotoxicity based on seed germination and plant growth. The extracted HA quantity and quality were significantly higher in frass than diet samples. Microbial profiling using 16S rRNA gene high-throughput sequencing revealed the enrichment of potential PGP genera, including Pseudoxanthomonas, Cellulomonas, Flavobacterium, and Mucilaginibacter. In addition, the actino-genera Cellulomonas, Demequina, Xylanimicrobium, Mycolicibacter, Nakamurella, and Glutamicibacter were positively correlated with HA content and quality parameters. This study highlights the potential of PBL systems in waste valorization and biofertilizer production as a novel approach for sustainable agriculture.