Efficiency of microbial fermentation on microbial shifts, enzymatic activity, and transcriptions in black soldier fly larvae during the sugarcane waste conversion

Sugarcane trash, consisting mainly of dried leaves, tops and cans, is often burned in the field, posing serious risks to human health, contributing to environmental pollution, and depleting soil nutrients. Black soldier fly larvae (BSFL) offer a promising solution for organic waste management by converting it into insect proteins. This study aimed to develop a microbial fermentation method to utilize sugarcane waste as feed for BSFL and investigate underlying mechanisms. Our results revealed that all fermented groups exhibited enhanced growth and developmental performance, with the combination of Bacillus subtilis, Enterococcus faecalis, and Saccharomyces cerevisiae leading to the highest increases in larval body weight, survival rate, substrate conversion efficiency, and protein content compared to the unfermented group. Metagenomic analysis revealed a notable increase in the phylum Firmicutes, along with its beneficial strains such as Bacillus licheniformis, B. safensis, B. pumilus, Cytobacillus kochii, and Lysinibacillus fusiformis, in the gut of BSFL reared on fermented sugarcane waste, leading to improved gut homeostasis and reduced pathogenic loads. Additionally, the BSFL fed with fermented sugarcane waste exhibited high abundances of carbohydrate-active enzymes (CAZymes) involved in cellulose, hemicellulose, and starch degradation at both class and family levels. Transcriptome analysis further indicated the upregulation of key genes associated with key physiological processes, such as carbohydrate metabolism, chitin biosynthesis, and defense mechanisms. Collectively, these findings demonstrate the synergistic potential of microbial fermentation and BSFL for sustainable sugarcane waste management while advancing the understanding of host-microbe-diet interactions in insect-based bioconversion systems.