Black soldier fly larvae (BSFL) are used industrially to bioconvert organic waste into valuable products, including insect protein, lipid, and frass. Diet mixing is a standard practice to improve digestibility and nutrient profiles of waste streams. However, this involves sourcing and transporting additional feedstocks, which can be costly. The gut microbiome plays a central role in host nutrition by mediating the breakdown of complex substrates, influencing metabolic efficiency, and shaping macronutrient utilisation. Thus, an opportunity exists to modulate the microbiome through targeted inoculation strategies to enhance BSFL waste-processing efficiency. However, a deeper understanding of microbiome-host-diet interactions is needed to enable microbiome intervention, potentially reducing the need for diet mixing while enhancing waste-processing outcomes.
D5 BSFL were fed one of four diets (Gainesville lab diet, GV; chicken feed, CF; oat milk waste, OT; and a 50:50 w/w mix of chicken feed and oat milk waste, CFOT) and sampled at D12. Impacts on diet consumption, larval weights, and larvae and frass nutrient profiles were analysed. Diet mixing positively impacted BSFL phenotype; total and average larval weights of CFOT-BSFL were significantly higher than all other treatments, largely due to higher lipid content.
BSFL guts were dissected into four segments (anterior midgut, mid midgut, posterior midgut, and hindgut) and subjected to multi-omics (metagenomics, metaproteomics, and metabolomics) analyses. Diet had a pronounced effect on the microbiome, particularly in the midgut, where composition and function differed most between treatments. Microbial taxa associated with cellulose and xylan degradation, and short-chain fatty acid (SCFA) biosynthesis, were enriched in CFOT-fed larvae. This suggests that differences in sugar and fatty acid metabolism contribute to altered macronutrient allocation between energy storage and direct expenditure across diets.
This study demonstrates that an integrated omics approach can disentangle complex diet-host-microbiome interactions, which may be used to further optimise an BSFL waste-bioprocessing system.