Swine manure from concentrated animal feeding operations (CAFOs) poses significant environmental and public health risks due to high nutrient, organic matter, and pathogen loads. Black soldier fly larvae (BSFL) composting has emerged as one of the sustainable and promising approaches for treating swine waste. BSFL’s ability to digest and treat swine waste is shaped and enhanced by the gut microbiome. Many factors, including moisture content, influence the composition and function of the gut microbiome. However, there is limited understanding of the role substrate moisture content plays. To address this knowledge gap, we conducted lab experiments at three moisture content levels (65%, 75%, and 85%) to assess the effect of moisture content on the larval gut microbiome. We measured larval growth, protein content, enzymatic activity, and contaminant removal performance. Microbial community composition in both larval gut and substrate was identified using 16S rRNA sequencing and multivariate analyses. Larvae reared at 65% moisture exhibited the highest protein content accumulation (40.8% dry matter) and achieved significantly higher removal efficiencies of total organic carbon (up to 85.4%), total nitrogen (up to 47.9%), and total phosphorus (up to 47.7%) compared to higher moisture treatments. Linear discriminant analysis effect size (LEfSe) analysis revealed that lower moisture conditions supported more diverse, functionally enriched communities associated with organic matter degradation, including taxa such as Bacillaceae, Paenibacillaceae, and Caryophanaceae, and genera such as Paenibacillus, Peribacillus, and Stenotrophomonas, whereas higher moisture levels favored anaerobic and fermentative taxa. Additionally, results from the principal component analysis show that the microbial communities in larvae reared at 65% moisture content are associated with enzymatic activities, indicating improved digestion and swine waste stabilization. Future research should explore techniques to enrich the identified microbial communities in larvae through microbial challenging and co-composting swine waste with raw materials associated with their production. This work plays a role in optimizing insect-based waste management systems and highlights the need for future research on microbial enhancement strategies and antimicrobial resistance dynamics.
Zhihan Sun (Fri,) studied this question.
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