Waste Valorization via Hermetia Illucens to Produce Protein-Rich Biomass for Feed: Insight into the Critical Nutrient Taurine

SIMPLE SUMMARY: The increasing demand of nutrients for food and feed imposes the urgent need to implement current nutritional resources while finding valuable alternative sources of fats and proteins. The present study aims to evaluate the efficiency to bioconvert the substrate proteins of vegetable wastes into valuable larval biomass by the insect Black Soldier Fly (BSF), Hermetia illucens. Here, we report that BSF larvae and prepupae show a high protein content characterized by different profiles of valuable amino acids, including taurine, a crucial nutrient for animal feed and future fish aquaculture. Moreover, we provide insights into the genetic basis of taurine biosynthesis in BSF for the first time and we show that the regulation of the genes associated with taurine synthesis influences the taurine content in BSF larvae and prepupae. These findings on peculiar BSF phenotypes encourage the utilization of larvae and/or prepupae to meet different nutritional requirements of fish species as alternative source of relevant amino acids including taurine. Notably, the bioconversion process by BSF represents a sustainable and economically interesting joint solution to meet the protein demand for animal and aquafeed in the next decades as well as a sustainable biotechnological tool for vegetable waste valorization. ABSTRACT: Insects have been recognized as sustainable alternative sources of nutrients for food and feed. The Black Soldier Fly (BSF), Hermetia illucens, is a particularly promising species for its great potential in the waste valorization to produce, during the bioconversion process, high-value fat and proteins that currently represent a valuable source for fish feed. The present study aims to evaluate the efficiency to use substrate proteins in two different BSF developmental stages as sustainable biotechnological tools for vegetable waste management. We provide insights into the nutritional values of both V instar larvae and prepupae in terms of valuable amino acids with special focus on taurine, a crucial nutrient for fish. Moreover, we cloned four key genes from BSF involved in the taurine biosynthesis pathway, 2-aminoethanethiol dioxygenase (Hiado), cysteine dioxygenase (Hicdo), cysteine sulfonate decarboxylase (Hicsad), and glutamate decarboxylase (Higad). The gene expression analysis in larvae and prepupae by qPCR showed development-specific profiles suggesting they influence the taurine content during BSF development. These findings showed peculiar phenotypes in larvae and prepupae that can be selected for different biotechnological applications as sustainable source of relevant amino acids and taurine to support the increasing demand for animal feed and aquafeed in the next decades.