Daniele Bruno

Insects offer promising opportunities for organic waste bioconversion; however, they cannot efficiently degrade synthetic polymers such as polyethylene terephthalate (PET). Here, we generated transgenic Drosophila melanogaster lines to express in vitro -evolved variants of two PET-degrading enzymes with distinct biochemical properties: an engineered Ideonella sakaiensis PETase variant (TS-ΔIsPET) and a leaf-branch compost cutinase variant (TA-ΔLCC). Both enzymes, fused to a Drosophila gut-derived secretory signal, were produced and secreted by both Drosophila cultured S2R ⁺ cells and transgenic larvae. Both enzymes were glycosylated upon secretion, a post-translational modification that did not abolish their catalytic activity. Notably, TA-ΔLCC displayed ∼6-fold higher esterase activity than TS-ΔIsPET in larval extracts and TA-ΔLCC-containing extracts depolymerised PET nanoparticles in vitro under enzyme-favourable conditions. Transgenic flies showed normal development, fertility and survival. Morphological and biochemical analysis confirmed that TA-ΔLCC expression did not alter midgut structure and function. Together, these results establish Drosophila melanogaster as a model for functional expression and comparative evaluation of engineered PET-degrading enzymes and identify TA-ΔLCC as a promising candidate for exploitation in insect species relevant to plastic contaminated waste bioconversion. Highlights: Transgenic D. melanogaster enables in vivo study of engineered PET enzymes Engineered TS-ΔIsPET and TA-ΔLCC are functional in larval extracts TA-ΔLCC was selected for PET nanoparticle assays due to higher pNPA activity D. melanogaster model enables comparative evaluation of PET-degrading enzymes

The mass rearing of insects for food and feed has emerged as a promising solution to food insecurity, protein production and waste valorisation. While outcomes such as growth and feed conversion efficiency have been examined for mass reared insects, the mechanisms underpinning these outcomes are poorly understood. To optimise the rearing of insects for food and feed and build towards efficient, scalable and productive systems, we must first therefore understand the mechanisms driving productivity and efficiency in common target species. By integrating emerging technologies across disciplines, we can begin to characterise these mechanisms to guide the optimisation of robust and standardised systems for efficient and scalable food and feed production. In this article, we explore opportunities for integrated and interdisciplinary thinking, and the use of emerging technologies to characterise the feeding physiology, digestive processes, microbiome-driven nutritional effects and behavioural regulation of insects commonly used for food and feed. We identify areas of synergy and interaction across research domains and provide a roadmap and call to action to catalyse uptake of these ideas across research and practice. By realising interdisciplinary integration and implementation of emerging technologies, we believe that an urgently required deeper mechanistic understanding of feeding-related processes is possible. This can, in turn, enable precision nutrition, improve system robustness and ensure consistent product quality.

Black soldier fly larvae (BSFL) have recently emerged as a promising and sustainable source of ingredients for animal feed due to their rapid growth and ability to efficiently bioconvert different organic waste and byproducts into high-nutritional-quality insect biomass. While substantial research has focused on the optimization of larval rearing conditions to improve the insect chemical composition, the interplay between diet composition and immune function in BSFL remains poorly understood. Herein, by comparing the effects of two diets on larvae’s performance, we showed that the dietary protein-to-carbohydrate (P:C) ratio influences growth and immunity in BSF. In detail, larvae fed on the diet with lower P:C ratio (0.32) reached a higher body weight than those grown on the substrate with higher P:C ratio (1.28), while developmental time and adult emergence rate were unaffected. In contrast, BSFL reared on the higher P:C ratio diet exhibited an enhanced immune response, characterised by an increased number of circulating haemocytes and upregulated expression of antimicrobial peptides genes, resulting in a more rapid bacterial clearance. These results demonstrate that the dietary P:C ratio differentially affects growth and immune investment in BSFL, revealing a trade-off between biomass accumulation and immune activation. Our findings provide novel insights into the nutritional modulation of insect immunity and have implications for optimizing rearing strategies for this species. Manipulating dietary P:C ratio could in fact provide a practical means to boost disease resistance and biosecurity in industrial BSFL production.

Metformin, a first-line treatment for type 2 diabetes, has gained attention as a promising neuroprotective agent due to its pleiotropic effects - including anti-inflammatory, anti-apoptotic, and autophagy-enhancing properties. Here we provide both preclinical and clinical evidence demonstrating the neuroprotective effects of metformin in the context of retinal ganglion cell (RGC) degeneration, a hallmark of glaucoma, a leading cause of irreversible blindness for which no direct RGC-neuroprotective therapies are currently available. In a mouse model of retinal ischemia/reperfusion injury systemic administration of metformin significantly prevented RGC loss and preserved retinal structure. Enhanced phosphorylation of AMP-activated protein kinase (AMPK) was observed, along with increased autophagosome formation and upregulation of key mitophagy markers - including LC3II, optineurin, and Parkin - indicating improved mitochondrial quality control mechanisms. Proteomic analysis revealed that metformin modulated several proteins implicated in mitochondrial respiratory function, ubiquitination, and intracellular trafficking, suggesting broader effects on retinal cellular homeostasis. Complementing our preclinical observations, a retrospective clinical study in diabetic patients with glaucoma showed that individuals treated with metformin maintained stable visual field (VF) parameters over a six-month period, whereas those treated with insulin exhibited significant VF deterioration. These findings position metformin as a promising intraocular pressure (IOP)-independent neurotherapeutic for slowing or preventing glaucomatous neurodegeneration.

Some insect species represent sustainable tools for the bioconversion of organic waste into valuable products, supporting the development of circular economy supply chains. However, their bioconversion efficiency is significantly reduced in the presence of recalcitrant polymers, such as plastics and lignocellulose. Although conventional pretreatment methods — chemical or thermal — are useful for degrading these compounds, they are often expensive and environmentally harmful. In contrast, insect holobionts (i.e. the host and associated gut microbiota) reared on recalcitrant polymers may offer a nature-based alternative. Indeed, microbial strains and enzymes capable of breaking down these polymers can be isolated from their gut, and their activity can be improved through biotechnology and synthetic biology. In this setting, highly efficient bioconversion agents, such as black soldier fly larvae, and wood-decomposing insects like termites and their symbionts, represent a rich and underexplored resource for tackling persistent waste challenges through microbial biotechnologies.

Coffee silverskin, the outer layer of the green coffee bean, represents a major by-product of the coffee industry derived from the roasting process. In recent years the development of sustainable and circular strategies to manage and valorise organic wastes and by-products has become increasingly relevant and the potential of coffee silverskin in food industry, cosmetics, and bioconversion applications is gaining attention. In the present work we addressed the valorisation of coffee silverskin through insect bioconversion using the larvae of the black soldier fly Hermetia illucens , one of the most promising bioconversion agents among insects. These larvae grow on a huge variety of organic substrates due to their outstanding adaptability, that is conferred by the plasticity of the midgut physiology and associated microbiota. Our results demonstrate that black soldier fly larvae were able to grow and develop on coffee silverskin. The larvae reduced this by-product by 25% and a high protein insect biomass (i.e. 56 g per 100 g of dry matter) was obtained. Interestingly, 25% of the hemicellulose fraction of coffee silverskin was degraded by the larvae. In addition, the larval gut microbiota, which plays a key role in larvae digestion adaptability and bioconversion, was shaped by growing the larvae on coffee silverskin and bacterial taxa involved in complex polysaccharide degradation were selected. In conclusion, black soldier fly larvae may represent (1) a valuable tool for the development of new and sustainable strategies for coffee silverskin bioconversion and valorisation, and (2) an effective bioincubator for the selection and isolation of microbial strains with peculiar degrading capacity.

T2 RNases are transferase‐type enzymes distributed across phyla, crucial for breaking down single‐stranded RNA molecules. In addition to their canonical function, several T2 enzymes exhibit pleiotropic roles, contributing to various biological processes, such as the immune response in invertebrates and vertebrates. This study aims at characterizing RNASET2 in the larvae of black soldier fly (BSF), Hermetia illucens, which are used for organic waste reduction and the production of valuable insect biomolecules for feed formulation and other applications. Given the exposure of BSF larvae to pathogens present in the feeding substrate, it is likely that the mechanisms of their immune response have undergone significant evolution and increased complexity. After in silico characterization of HiRNASET2, demonstrating the high conservation of this T2 homolog, we investigated the expression pattern of the enzyme in the fat body and hemocytes, two districts mainly involved in the insect immune response, in larvae challenged with bacterial infection. While no variation in HiRNASET2 expression was observed in the fat body following infection, a significant upregulation of HiRNASET2 synthesis occurred in hemocytes shortly after the injection of bacteria in the larva. The intracellular localization of HiRNASET2 in lysosomes of plasmatocytes, its extracellular association with bacteria, and the presence of a putative antimicrobial domain in the molecule, suggest its potential role in RNA clean‐up and as an alarm molecule promoting phagocytosis activation by hemocytes. These insights contribute to the characterization of the immune response of Hermetia illucens larvae and may facilitate the development of animal feedstuff enriched with highly valuable BSF bioactive compounds.

The saprophagous larvae of Hermetia illucens show promising potential as effective agents for bioconverting organic waste and by-products into valuable biomass. Their capability to efficiently transform organic substrates, varying in nutrient content, origin, texture, and moisture, is strictly correlated with the morphofunctional complexity of their digestive system and the associated microbiota. In addition, post-ingestion mechanisms are set in motion to regulate the midgut activity depending on the feeding substrate, thus ensuring the nutritional requirements of the larvae. This study aims to assess the capability of H. illucens larvae to grow and biotransform the organic fraction of municipal solid waste (OFMSW). In particular, the larvae were reared on substrates mimicking the OFMSW with different nutrient content, and their growth and bioconversion performance, as well as the quality of larval and pupal biomass were evaluated. Our results demonstrate that the nutritional composition of the rearing substrates had minimal impact on the efficiency of the bioconversion process and on the protein, lipid, and chitin content of the insect biomass. This was due to a fine transcriptional regulation of genes encoding enzymes involved in protein, polysaccharide, and lipid digestion in midgut cells. As a consequence, larvae reared on OFMSW with the lowest protein, starch, and lipid content exhibited a significant increase in protease, amylase, and lipase activities. Overall, this study highlights the value of H. illucens larvae in valorising the OFMSW, demonstrating that variations in its composition do not significantly affect the quality of the bioconversion process. These findings hold significant practical implications as current strategies for OFMSW treatment remain unsatisfactory and innovative approaches are needed to enhance bio-waste recycling and reduce the environmental impact of waste management.

In recent years the entomological landscape has witnessed substantial progress in the promotion of insects for food and feed purposes. In particular, the black soldier fly (BSF) sector is experiencing an unprecedented expansion and is attracting growing attention from both researchers and entrepreneurs. Despite the well-established supply chain based on the valorisation of waste and by-products by BSF larvae for producing feedstuff, the BSF industry is considering alternative challenging substrates for rearing the larvae and exploring novel applications of bioactive molecules from BSF beyond animal feed. This editorial challenges the conventional boundaries of the insects for food and feed sector, and delves into the innovative use of BSF proteins, lipids, and chitin, pointing out diverse opportunities across the biomedical, biotechnological, agricultural, zootechnical, and environmental sectors that could further propel the utilisation of this insect.