Nutritional enrichment of black soldier fly larvae towards a sustainable protein food supplement for livestock and poultry production.

Abstract

Black soldier fly larvae (Hermetia illucens, BSFL) offer a hyper local, low-carbon sustainable, circular bioeconomic pathway for organic waste valorization and the production of alternative protein sources for livestock and poultry. This study presents a nanomineral biofortification strategy to enhance the nutritional profile of BSFL reared on two distinct feed substrates: conventional industry-standard feed (wheat bran and layer mash) and brewery spent grains. Monodisperse nanoparticles of zinc oxide, manganese oxide, copper oxide and elemental selenium were synthesized using a spinning disc reactor and incorporated into alginate gels (0.25-5 % w/v) and aqueous dispersions (0.05-0.1% w/v), to fortify the industry-standard feed and brewery spent grains. Proximate analysis showed that nanomineral supplementation significantly improved BSFL protein content (up to 40.8%) and fat levels (up to 30.3%), while modulating fiber and ash composition. Elemental analysis revealed that mineral bioaccumulation in BSFL was influenced by both substrate type and nanoparticle formulation. Alginate gels promoted zinc and selenium uptake, whereas aqueous dispersions enhanced manganese and copper accumulation. Notably, BSFL reared on fortified brewery spent grains exhibited higher zinc and manganese accumulation compared to those reared on conventional feed highlighting brewery spent grains potential as a superior base substrate for targeted mineral enrichment. Multi-element nanomineral mix treatments showed no antagonistic interactions, indicating synergistic uptake potential. BSFL grown on fortified brewery spent grains demonstrated enhanced bioconversion efficiency, effectively transforming low-value agro-industrial waste into high-quality insect biomass. The accumulated zinc in BSFL was more bioavailable to poultry than a standard zinc oxide feed additive in the completed broiler feed. This scalable approach enables an adoption tipping point for this emerging alternative protein solution by reducing the cost of production of BSFL and adding value to the insect meal end product.