Impact of Substrate Type and Developmental Stage on Nutrient Composition and Convergence Efficiency of Hermetia illucens Larvae

This study investigates the bioconversion efficiency and nutrient accumulation in black soldier fly (BSF; <italic>Hermetia illucens</italic>), focusing on the effects of feeding on two different substrates (tofu by-products and food waste) and harvesting at two developmental stages (larvae and prepupae) within a 2×2 factorial arrangement. The growth performance, conversion efficiency, nutrient composition, amino acid profile, fatty acid composition, and nutrient composition of BSF meal were assessed. Results indicated that BSF reared on tofu by-products exhibited superior weight gain compared to those fed food waste, with significant enhancements observed in weight, length, and width upon harvesting at the prepupae stage. Moreover, tofu by-products promoted higher bioconversion rates, protein conversion efficiency, and lipid yield, while food waste favored lipid conversion. Analysis of nutrient composition revealed higher crude protein content in BSFs fed tofu by-products, with elevated levels of crude protein, ether extract, and chitin in prepupae-stage BSFs. Higher concentrations of isoleucine, leucine, and tryptophan observed in tofu by-product-fed BSFs. Conversely, BSFs harvested at the prepupae stage exhibited increased levels of threonine, alanine, and tyrosine, regardless of substrate. Higher proportions of α-linolenic acid (C18:3n3) and docosahexaenoic acid (C22:6n3) were observed in tofu by-product-fed BSF. Conversely, BSFs harvested at the larval stage displayed higher levels of saturated fatty acids, including lauric acid (C12:0) and myristic acid (C14:0). In conclusion, tofu by-products emerged as a promising substrate for enhancing essential amino acid and unsaturated fatty acid content in BSFs, while harvesting at the prepupae stage offered advantages in nutrient density and storage stability of the harvested biomass.