Substrate Composition Modulates Agri-Food Waste Bioconversion by Yellow Mealworm (Tenebrio molitor) Larvae Under...

Yellow mealworm (Tenebrio molitor) larvae can convert low-value organic residues into insect biomass, but their performance depends on substrate composition and feeding strategy. We evaluated vegetable wastes, okara-wheat-bran diets and kitchen waste-wheat-bran mixtures under a dynamic feeding regime. Ingredient and proximate compositions were determined, and larval growth, fresh-weight-based waste reduction (WR), bioconversion rate (BCR) and feed conversion efficiency (FCE), pupal output, nutritional composition and heavy metal contents were assessed. Among vegetable wastes, potato showed the highest numerical WR (95.18 ± 0.73%) and relatively high BCR and FCE, whereas pumpkin produced the most pupae (109.00 ± 8.62 per replicate). Cabbage showed reduced biomass conversion and pupal output. In the okara trial, 40% okara showed the highest numerical WR (75.88 ± 0.39%), 10% okara maximized FCE (15.83 ± 0.38%) and 20% okara produced the greatest pupal output. Principal component analysis (PCA) indicated treatment-specific conversion and developmental patterns, but was interpreted as an exploratory association analysis rather than a causal model. Kitchen waste mixtures increased the relative fat proportion and reduced the relative protein proportion of larvae; the 3:2 mixture increased crude fat to 37.90 ± 0.22% while retaining 57.39 ± 0.40% crude protein. Higher kitchen waste inclusion was associated with greater larval arsenic (As) content, reaching 0.803 ± 0.001 mg/kg in the 5:2 treatment. Substrate composition should therefore be optimized together with conversion efficiency, product quality and safety screening.