No abstract

Insects are becoming increasingly relevant as protein sources in food and feed. The Black Soldier Fly (BSF) is one of the most utilized, thanks to its ability to live on many leftovers. Vegetable processing industries produce huge amounts of by-products, and it is important to efficiently rear BSF on different substrates to assure an economical advantage in bioconversion and to overcome the seasonality of some leftovers. This work evaluated how different substrates affect the protein and amino acid content of BSF. BSF prepupae reared on different substrates showed total protein content varying between 35% and 49% on dry matter. Significant lower protein contents were detected in BSF grown on fruit by-products, while higher contents were observed when autumnal leftovers were employed. BSF protein content was mainly correlated to fibre and protein content in the diet. Among amino acids, lysine, valine and leucine were most affected by the diet. Essential amino acids satisfied the Food and Agricultural Organization (FAO) requirements for human nutrition, except for lysine in few cases. BSF could be a flexible tool to bio-convert a wide range of vegetable by-products of different seasonality in a high-quality protein-rich biomass, even if significant differences in the protein fraction were observed according to the rearing substrate.

In this study proteins extracted from prepupae of Hermetia illucens, also known as black soldier fly, are investigated as promising base for a new type of bioplastics for agricultural purposes. Design of experiments techniques are employed to perform a rational study on the effects of different combination of glycerol as plasticizer, citric acid as cross‐linking agent and distilled water as solvent on the capability of proteins to form a free‐standing film through casting technique, keeping as fixed the quantity of proteins. Glycerol shows interesting properties as plasticizer contributing to the formation of homogenous and free‐standing film. Moreover, mechanical and thermal characterizations are performed to estimate the effect of increasing amounts of proteins on the final properties and thickness of the specimens. Proteins derived from H. illucens can be successfully employed as base for bioplastics to be employed for agricultural purposes.

In this study, an organic nitrogen-based coating was developed based on black soldier fly (BSF) prepupae reared on poultry dejections and deposited on ceramic lightweight aggregates (LWAs), containing phosphorous (P) and potassium (K) from agroresidues, leading to a complete nitrogen, phosphorus, and potassium (NPK) fertilizer. To obtain a resistant coating with good adhesion to LWAs, different plasticizing agents were tested (e.g., glycerol, cellulose, and polyethylene glycol). The coating formulation was optimized through a design-of-experiment (DoE) approach to correlate the effect of each mixture component on the coating’s performance. BSF biomass was characterized through chemical and thermal routes, as well as the final coated LWAs, confirming their general agreement to fertilizer’s requirements. Release tests in static conditions highlighted the barrier action of the coating, preventing uncontrolled release of potassium and phosphorus contained in the LWAs as well as the release of nitrogen after 21 days (near to 20%). Germination and growth tests indicated a valuable increase of the growth index, whereas the germination process is limited by the coating barrier effect. This work proposes a new product in the field of slow-release fertilizers designed by rational methodologies and innovative materials based on waste valorization, fully in agreement with a circular economy perspective.

The cradle-to-grave life cycle assessment (LCA) was applied to the preparation of biomaterials derived from proteins, extracted from black soldier fly (BSF) prepupae, after the larvae were reared on poultry manure-based organic waste. To obtain higher value-added biomolecules, extraction represents the fundamental step. Therefore, the environmental sustainability assessments of different extraction/fractionation procedures were compared. In this way, it is possible to consider also their environmental performances in addition to the purity, yield, and integrity of the extract. A chemical method characterized by a one-step protein extraction was compared to an enzymatic-assisted protocol, employing Bacillus licheniformis protease. Surprisingly, the enzymatic approach resulted for the 31.87% more environmentally impacting with respect to the chemical method, despite its lack of organic solvents and reduction of alkaline and acid solutions employed. Particularly, the long time necessary for the enzymatic hydrolysis significantly contributed to the environmental impact of this protocol. Therefore, improvements such as biomass pretreatment procedures or the use of different proteolytic enzymes (e.g., operating at lower temperatures and in shorter times) are needed. Moreover, to reduce the environmental load of the protein fraction, attention should also be given to increase extraction yields of lipids and chitin biomolecules obtainable from BSF prepupae, due to the biorefinery approach under which this study was considered.