Silkworm excrement, a byproduct of the sericulture industry, is rich in organic compounds and presents a sustainable substrate for enzyme production. This study investigates the potential of silkworm excrement as a substrate for pectinase production using Aspergillus niger submerged fermentation. Single-factor experiments and a Box–Behnken Design (BBD) were employed to identify and optimize the key medium components and their interactions. Results indicated that the optimal concentrations for maximum pectinase activity were CaCl₂ at 0.437 g/L, orange peel powder at 4.223 g/L, (NH₄)₂SO₄ at 15.761 g/L, and bran at 33.590 g/L. The optimized conditions achieved a pectinase activity of 20.505 U/mL, validating the robustness of the RSM model. This approach not only maximizes enzyme activity but also presents a sustainable and cost-effective method for utilizing a byproduct in the sericulture industry, aligning with principles of circular economy and waste minimization.

This study evaluates the synergistic effects of silkworm feces and earthworms on nutrient-poor acidic red soils in Guangxi, China. Using 16S rDNA amplicon sequencing, soil samples from untreated fields, silkworm feces, earthworm gut contents, and soils treated with silkworm feces combined with three earthworm densities (50, 80, and 110 worms/kg) were compared. The earthworm gut microbiome increased in diversity in a density-dependent manner, while treated soils displayed enhanced microbial richness-with the 80 worms/kg treatment showing the highest diversity (605 genera). Random Forest analysis identified key bacterial genera, and co-occurrence networks pinpointed potential keystone taxa. PICRUSt2 predicted enrichment of pathways for xenobiotic biodegradation, carbohydrate metabolism, and secondary metabolite biosynthesis. These findings demonstrate that integrating silkworm feces with an optimal earthworm density improves soil microbial diversity and function, offering insights for sustainable organic waste management and soil health.