Effect of entomopathogenic fungus Beauveria bassiana on the growth characteristics and metabolism of black soldier fly larvae

Beauveria bassiana is an entomopathogenic fungus widely used in agriculture to reduce populations of various pests. However, when agricultural waste is utilized for organic recycling, B. bassiana has the potential to impact recycling performance, by affecting the survival, and body mass of decomposing organisms (such as insect's larvae). Additionally, in natural conditions where decayed organic matter contains a high load of different entomopathogenic organisms, larval growth may be affected when consumed or in contact. In a laboratory study, we aimed to comprehend the effects of B. bassiana on the growth characteristics and larval metabolism of the black soldier fly larvae, which is a known decomposing insect. The experiments used both feeding (mixing the spores with the diet, hereafter BF) and contact treatments (by dipping the larva in the spores solution, hereafter BD), and were compared to a water-treated control group. The BF treatment significantly reduced larval body weight, adult emergence, and adult weight compared to both the control and the BD treatment. Furthermore, an analysis of hemolymph metabolites, categorized by class, indicated a higher accumulation of metabolites belonging to the purine and purine derivative classes, as well as carboxylic acids and their derivatives, including peptides and oligopeptides, indicating potential disruption of protein synthesis or degradation caused by the BF treatment. Pathway enrichment analysis showed significant alterations in purine metabolism and D-Arginine and D-ornithine metabolism compared to the control. Taurine and hypotaurine metabolism were significantly altered in the BD treatment compared to the control but not significantly enriched in the BF treatment. Our results suggest that the BF treatment impairs protein synthesis or degradation, affecting larval growth characteristics. Future studies should explore innate immunity-related gene expression and antimicrobial peptide production in BSF larvae to understand their immunity to pathogens.

Effects of three major nutrient contents, compost thickness and treatment time on larval weight, process performance and residue component in black soldier fly larvae (Hermetia illucens) composting

The cellulose content in vegetable waste (VW) is high and cannot be directly digested by black soldier fly larvae (BSFL). In this study, in order to treat VW using BSFL composting, kitchen waste (KW) is used as the only nutritional supplement for VW to analyze the effects of the different contents of crude protein (CP), crude fat (EE), carbohydrate (3C), compost thickness (CT), and treatment time on the larval weight (LW), survival rate (SR), dry matter reduction rate (DMR), bioconversion rate (BCR), physical and chemical properties of BSFL sand and changes in the microbial community. Our results showed that when the average 3C content increased by 40%, the average LW increased by 47.6%, and the SR, DMR, BCR, and organic matter (OM) content increased by 16.82%, 8.5%, 4.77%, and 3.86%, respectively. In contrast, when the average compost thickness increased by 5 cm, the average weight of BSFL decreased by 22.64%, while the SR of larvae, DMR, BCR, OM, and total nutrients (TN + P₂O₅ + K₂O) decreased by 5%, 5.2%, 4.42%, 9.6%, and 0.78%, respectively. Germination test showed that BSFL sand alone could not be used as soilless culture substrate. After BSFL treatment, we found that the dominant phyla in BSFL sand were Firmicutes (95.77%), Proteobacteria (2.54%), Actinobacteria (0.74%), and Chloroflexi (0.6%). Our results indicate that BSFL composting is an effective method of treating VW, and 3C content and CT have a significant effect on BSFL composting.