Exogenous microbial agents interact with housefly larvae to reshape the microbiome and accelerate cellulose degradation in silkworm (Bombyx mori) excrement

Abstract

Silkworm (Bombyx mori) excrement accumulates in large quantities and causes severe environmental pollution, with highly crystalline cellulose limiting efficient resource utilization. The development of effective cellulose-degrading bacterial technologies is crucial for advancing biotechnological applications. This study investigated the effects of exogenous microbial agents and housefly larvae composting on cellulose biodegradation in silkworm excrement. After six days, the cellulose content decreased by 52.6%, 58.2%, and 64.0% in the treatment groups, respectively, which was significantly greater than the 39.41% reduction in the control group without exogenous agents. The combination of exogenous microbial agents and housefly larvae reshaped the bacterial community, increasing the relative abundance of cellulose-degrading taxa. Specifically, Firmicutes and Actinobacteria were enriched, and the abundances of Bacillus, Pseudomonas, and Cellulosimicrobium increased. Functional predictions via PICRUSt indicated that carbohydrate metabolism was predicted to dominate bacterial activity, while Tax4Fun analysis suggested that exogenous agents were associated with increased predicted abundances of endo-β-1,4-glucanase and exo-β-1,4-glucanase genes in excrement, which may relate to accelerated cellulose degradation. This study suggests that the combination of exogenous microbial agents and housefly larvae could promote cellulose-degrading bacterial populations and the genetic potential for cellulase activity, representing a possible strategy for silkworm excrement bioconversion