ZhiJian Zhang

Black soldier fly larvae (Hermetia illucens L., BSFL) efficiently degrade lignocellulosic waste despite lacking endogenous lignocellulolytic enzymes, indicating a critical dependence on gut-associated microbiota. However, how BSFL are associated with the enrichment and spatial organization of lignocellulose-degrading symbionts within the gut remains poorly understood. We show that BSFL establish a spatially structured microbiome through gut compartment-specific immune regulation. Axenic larvae showed negligible lignocellulose degradation, whereas microbiota-associated larvae achieved ~ 33.3%, confirming microbial dependence. Antimicrobial peptides, including cecropin and defensin, were highly expressed in the anterior midgut, forming a selective barrier. In contrast, the posterior midgut showed reduced immune activity via peptidoglycan recognition proteins (PGRP-LB, PGRP-SC). Concurrently, host glycosylation-related genes (C1galt1, GlcAT-P, FUT8/11) were significantly upregulated in the posterior midgut (17-19 TPM), representing a 4-fivefold increase relative to the anterior region (p < 0.01). This region was correspondingly enriched in carbohydrate-active symbionts producing glycoside hydrolases, including galactosidases, fucosidases, and mannosidases, suggesting that upregulated glycan biosynthesis may provide sustained nutrient availability for microbial taxa with corresponding carbohydrate-utilizing capacities. Such compartmentalized immune-metabolic coordination is consistent with a potentially conserved strategy for modulating immune tolerance and fostering symbiont recruitment. Collectively, our findings define a compartmentalized "Dismissing-then-Recruiting" strategy for microbiome assembly in BSFL, which is associated with the structuring of functional symbiont communities for efficient lignocellulose bioconversion, thereby elucidating novel principles for sustainable waste management. Video

Black soldier fly larvae have been proven to reduce greenhouse gas emissions in the treatment of organic waste. However, the microbial mechanisms involved have not been fully understood. The current study mainly examined the dynamic changes of carbon and nitrogen, greenhouse gas emissions, the succession of microbial community structure, and changes in functional gene abundance in organic waste under larvae treatment and non-aeration composting. Thirty percent carbon and 55% nitrogen in the organic waste supplied were stored in larvae biomass. Compared to the non-aeration composting, the larvae bioreactor reduced the proportion of carbon and nitrogen converted into greenhouse gases (CO₂, CH₄, and N₂O decreased by 62%, 87%, and 95%, respectively). 16S rRNA sequencing analysis indicated that the larvae bioreactor increased the relative abundance of Methanophaga, Marinobacter, and Campylobacter during the bioprocess, enhancing the consumption of CH₄ and N₂O. The metagenomic data showed that the intervention of larvae reduced the ratio of (nirK + nirS + nor)/nosZ in the residues, thereby reducing the emission of N₂O. Larvae also increased the functional gene abundance of nirA, nirB, nirD, and nrfA in the residues, making nitrite more inclined to be reduced to ammonia instead of N₂O. The larvae bioreactor mitigated greenhouse gas emissions by redistributing carbon and nitrogen and remodeling microbiomes during waste bioconversion, giving related enterprises a relative advantage in carbon trading.

Black soldier fly larvae (BSFL) have been proven to reduce greenhouse gas emissions in the treatment of organic waste (e.g., domestic biodegradable waste, DBW). However, the microbial mechanisms involved have not been fully understood. The current study mainly examined the dynamic changes of carbon and nitrogen, greenhouse gas emissions, the succession of microbial community structure, and changes in gene abundance in DBW under BSFL treatment (LT) and non-aeration composting (NC). We found that of the organic waste supplied, 29.9% carbon and 55.0% nitrogen were stored in BSFL. For every 1kg of dry matter of organic waste consumed, 655 g CO₂, 0.80 mg CH₄, and 2.26 mg N₂O were emitted from LT, significantly lower than those from NC. 16S rRNA gene sequencing results showed that the BSFL increased the relative abundance of Methanophaga, Marinobacter, and Campylobacter during the bioprocess, enhancing the consumption of CH₄ and N₂O. The metagenomic data showed that the BSFL reduced the ratio of (nirK + nirS + nor)/nosZ in the residues, thereby reducing the emission of N₂O. In addition, it increased the functional gene abundance of nirA, nirB, nirD, and nrfA, making nitrite more inclined to be reduced to ammonia. The BSFL mitigated greenhouse gas emissions by redistributing carbon and nitrogen and remodeling the community and function of microbiomes during the DBW bioconversion.