Towards Functional Fertilisers: Feed Composition Shapes Microbial Community structure and Viability in Black Soldier Fly (Hermetia illucens) Frass

The microbiome of black soldier fly larvae (BSFL) frass is gaining attention for its potential as an organic fertiliser in sustainable agriculture. This study explores how different feed substrates influence the microbial communities in frass, which are vital for plant growth. Five feed substrates, including industrial side streams, were examined using metabarcoding methods, specifically 16S V3-V4 and ITS2 amplicon sequencing, alongside Sanger sequencing for taxonomic classification. Nutrient analysis was performed, and viable populations were quantified through culture-based methods. The feed type was the primary factor shaping frass microbiota, with distinct communities corresponding to the nutrient profiles of the substrates. Thermal hygienisation showed variable effects on viable counts but minimal influence on overall community structure. These findings highlight the importance of microbiome characterization in designing feed to optimize frass microbial profiles for enhanced biofertiliser efficacy.