Black soldier fly, Hermetia illucens as a potential innovative and environmentally friendly tool for organic waste management: A mini-review

Strategic approach for converting fat-rich food waste into high-quality biodiesel using black soldier fly larvae for sustainable bioenergy

Food waste (FW) comprises carbohydrates, proteins, lipids, and water, posing technical challenges for effective treatment and valorisation. This study addresses these challenges by using black soldier fly larvae (BSFL) as a bioconversion medium to transform FW into biodiesel (BD). BSFL predominantly consumed the carbohydrates and proteins in FW (81 wt%), while showing a lower preference for lipids (<50 wt% consumed). Notwithstanding the lower consumption of lipids in the FW than that of carbohydrates and proteins, BSFL had a high lipid content (48.3 wt%). The subsequent conversion of the lipids extracted from BSFL into BD was tested via catalytic (acid/alkali) and non-catalytic transesterification processes. The BD yield from catalytic transesterification was lower than that from non-catalytic transesterification because of the low tolerance against free fatty acids (FFAs). BD was also produced from the lipid-concentrated residual FW through non-catalytic transesterification. Although the FW residue extracts contained high amounts of FFAs (49.9 wt%), non-catalytic transesterification displayed a high BD yield (92.4 wt%; yields from catalytic transesterification: < 80.0 wt%). Moreover, blending the BD derived from the BSFL and FW residue extracts enhanced the fuel properties. The BSFL-assisted FW management efficiently reduced FW by 90 wt% while producing a high-quality BD.

Wheat starch processing by-products as rearing substrate for black soldier fly: does the rearing scale matter?

Rearing scale may influence black soldier fly (BSF) larvae traits when they are fed on a single diet, but different feeding substrates have not been tested yet. This study evaluated the effects of wheat starch processing by-products-based diets on growth performance, bioconversion efficiency, and nutritional profile of BSF larvae reared in different scales. Four diets (D1 and D2 [isonitrogenous, isolipidic and isoenergetic]; D3 and D4 [displaying 1:1 and 1:2 as protein to carbohydrate ratios, respectively]) were tested at 3 rearing scales (4 replicate boxes/diet, with a constant volume [0.84 cm3]/larva and feed [0.7 g]/larva): 1) small (S; 12 × 12 cm, substrate height: 4 cm, 686 6-day-old larvae (6-DOL)/box), 2) medium (M, 32 × 21 cm, substrate height: 7 cm, 5 600 6-DOL/box), and 3) large (L, 60 × 40 cm, substrate height: 7 cm, 20 000 6-DOL/box). Larval weight was recorded at the beginning of trial and every 4 days, and growth rate (GR), specific growth rate (SGR), feed conversion ratio (FCR), survival, bioconversion efficiency corrected for residue (BER), reduction rate (RR), and waste reduction index (WRI) calculated at the end of larval growth (frass DM ≥ 55%). Substrate pH, T and height were measured at the beginning, every 4 days, and end of trial. Larval proximate composition was analysed at the end of trial. Data were analysed by generalised linear mixed model (SPSS software, P < 0.05). The D1 larvae showed higher weight, GR, SGR and WRI (along with higher substrate T) than D2 at M scale, while increased SGR and FCR - as well as decreased survival, RR and WRI - were observed in D2 larvae at S scale (P < 0.05). Larval CP and ether extract (EE) contents were influenced by M and L scales only, being higher in D2 group than in D1 (P < 0.001). Differently, decreased ash was recorded in D2 larvae when reared at S and M scales, while L scale revealed higher ash in D2 group than D1 (P < 0.001). The D3 larvae displayed greater weight, SGR, survival, RR and WRI (along with greater substrate T) than D4 at M scale, with increased survival and substrate T being also highlighted in L scale (P < 0.05). The D3 larvae also showed lower DM and EE - as well as higher CP - than D4 at all the rearing scales (P < 0.001). In conclusion, D1 and D3 led to better BSF larval growth performance, bioconversion efficiency and nutritional profile mainly at M and L scales, as a consequence of their ability to facilitate larval aggregation and, in turn, allow achieving a higher substrate T.

Unlocking the significant worldwide potential of better waste and resource management for climate mitigation: with particular focus on the Global South

Numbers do matter; the Intergovernmental Panel on Climate Change (IPCC)'s 2010 data that the waste sector is responsible for just 3% of global greenhouse gas (GHG) emissions has led to the misperception that solid waste management (SWM) has little to contribute to climate mitigation. Global efforts to control methane emissions and divert organic waste from landfills had already reduced direct emissions. But end-of-pipe SWM has also been evolving into more circular waste and resource management, with indirect GHG savings from the 3Rs (reduce, reuse, recycle) which IPCC accounts for elsewhere in the economy. The evidence compiled here on both direct emissions and indirect savings demonstrates with high confidence that better waste and resource management can make a significant contribution to climate mitigation, and must form a core part of every country's nationally determined contribution. Even the most advanced countries can still achieve much from the 3Rs. In the Global South, the challenge of extending waste collection to all and stopping open dumping and burning (sustainable development goal 11.6.1), essential to improve public health, can be turned into a huge opportunity. Moving early to divert waste from landfill by separation at source and collecting clean organic and dry recycling fractions, will mitigate global GHG emissions, slash ocean plastics and create decent livelihoods. But this can only happen with targeted climate, plastics and extended producer responsibility finance; and help to local communities to help themselves.

Diverting organic waste from landfills via insect biomanufacturing using engineered black soldier flies (Hermetia illucens)

A major roadblock towards the realisation of a circular economy are the lack of high-value products that can be generated from waste. Black soldier flies (BSF; Hermetia illucens) are gaining traction for their ability to rapidly consume large quantities of organic wastes. However, these are primarily used to produce a small variety of products, such as animal feed ingredients and fertiliser. Using synthetic biology, BSF could be developed into a novel sustainable biomanufacturing platform to valorise a broader variety of organic waste feedstocks into enhanced animal feeds, a large variety of high-value biomolecules including industrial enzymes and lipids, and improved fertiliser.

Whole-genome sequencing of two captive black soldier fly populations: Implications for commercial production

Black soldier fly (BSF; Hermetia illucens) is a promising insect species for food and feed production as its larvae can convert different organic waste to high-value protein. Selective breeding is one way to optimize production, but the potential of breeding is only starting to be explored and not yet utilized for BSF. To assist in monitoring a captive population and implementing a breeding program, genomics tools are imperative. We conducted whole genome sequencing of two captive populations separated by geographical distance - Denmark (DK) and Texas, USA (TX). Various population genetics analyses revealed a moderate genetic differentiation between two populations. Moreover, we observed higher inbreeding in the DK population, and the detection of a subpopulation within DK population aligned well with the recent foundation of the DK population from two captive populations. Additionally, we generated gene ontology annotation and variants annotation for wider potential applications. Our findings establish a robust marker set for research in population genetics, facilitating the monitoring of inbreeding and laying the groundwork for practical breeding programs for BSF.

Microbial dynamics and vertical transmission of Escherichia coli across consecutive life stages of the black soldier fly (Hermetia illucens)

BACKGROUND

The black soldier fly (BSF, Hermetia illucens L.) is one of the most promising insects for bioconversion of organic waste, which often carry a high microbial load with potential foodborne pathogens. Although horizontal transmission (from rearing substrate to larvae) has been extensively studied, less is known about vertical transmission of microorganisms, and particularly of foodborne pathogens, across different BSF life stages.

RESULTS

This study investigated the microbial dynamics and vertical transmission of Escherichia coli across different life stages (larvae, prepupae, pupae and adults) of one BSF life cycle and its associated substrate (chicken feed) and frass, based on a combination of general microbial counts (based on culture-dependent techniques) and the bacterial community composition (based on 16S rRNA gene sequencing). Multiple interactions between the microbiota of the substrate, frass and BSF larvae were affirmed. The larvae showed relative consistency among both the microbial counts and bacterial community composition. Diversification of the bacterial communities started during the pupal stage, while most notable changes of the microbial counts and bacterial community compositions occurred during metamorphosis to adults. Furthermore, vertical transmission of E. coli was investigated after substrate inoculation with approximately 7.0 log cfu/g of kanamycin-resistant E. coli, and monitoring E. coli counts from larval to adult stage. Although the frass still contained substantial levels of E. coli (> 4.5 log cfu/g) and E. coli was taken up by the larvae, limited vertical transmission of E. coli was observed with a decreasing trend until the prepupal stage. E. coli counts were below the detection limit (1.0 log cfu/g) for all BSF samples from the end of the pupal stage and the adult stage. Additionally, substrate inoculation of E. coli did not have a substantial impact on the bacterial community composition of the substrate, frass or different BSF life stages.

CONCLUSIONS

The fluctuating microbial counts and bacterial community composition underscored the dynamic character of the microbiota of BSF life stages. Additionally, vertical transmission throughout one BSF life cycle was not observed for E. coli. Hence, these findings paved the way for future case studies on vertical transmission of foodborne pathogens across consecutive BSF life stages or other insect species.

Insects to the rescue? Insights into applications, mechanisms, and prospects of insect-driven remediation of organic contaminants

Traditional and emerging contaminants pose significant human and environmental health risks. Conventional physical, chemical, and bioremediation techniques have been extensively studied for contaminant remediation. However, entomo- or insect-driven remediation has received limited research and public attention. Entomo-remediation refers to the use of insects, their associated gut microbiota, and enzymes to remove or mitigate organic contaminants. This novel approach shows potential as an eco-friendly method for mitigating contaminated media. However, a comprehensive review of the status, applications, and challenges of entomo-remediation is lacking. This paper addresses this research gap by examining and discussing the evidence on entomo-remediation of various legacy and emerging organic contaminants. The results demonstrate the successful application of entomo-remediation to remove legacy organic contaminants such as persistent organic pollutants. Moreover, entomo-remediation shows promise in removing various groups of emerging contaminants, including microplastics, persistent and emerging organic micropollutants (e.g., antibiotics, pesticides), and nanomaterials. Entomo-remediation involves several insect-mediated processes, including bio-uptake, biotransfer, bioaccumulation, and biotransformation of contaminants. The mechanisms underlying the biotransformation of contaminants are complex and rely on the insect gut microbiota and associated enzymes. Notably, while insects facilitate the remediation of contaminants, they may also be exposed to the ecotoxicological effects of these substances, which is often overlooked in research. As an emerging field of research, entomo-remediation has several knowledge gaps. Therefore, this review proposes ten key research questions to guide future perspectives and advance the field. These questions address areas such as process optimization, assessment of ecotoxicological effects on insects, and evaluation of potential human exposure and health risks.

Microbial fermentation and black soldier fly feeding to enhance maize straw degradation

This study used an innovative synergistic microbial and insect approach to treat maize straw and kitchen waste substrates, including cyclic microbial fermentation and feeding of black soldier fly larvae (BSFL) using the fermented substrate. Increasing cycle numbers led to significantly increased cellulose, hemicellulose, and lignin degradation rates (DR) in the maize straw, which increased by 68.28%, 81.43% and 99.95%, respectively, compared to those in the blank group without frass addition. Moreover, according to the experimental results, it was revealed that the structure of lignocellulose, the composition and structure of the bacterial community in the BSFL gut and frass changed significantly after the addition of the previous cycle of frass treatment. Moreover, the differences in amplicon sequence variants (ASVs) between the gut and frass further increased. The relative abundances of Enterococcus and Actinobacteria in the gut and Gammaproteobacteria_unclassified and Dysgonomonas in the frass increased significantly, which may play a more positive role in lignocellulose degradation. In conclusion, this study showed that frass fermentation + BSFL feeding to degrade straw is a promising method and that frass fermentation is beneficial for the whole cycle. Furthermore, these findings underscore the beneficial impact of frass fermentation on the entire cycle.

Larval biomass production from the co-digestion of mushroom root waste and soybean curd residues by black soldier fly larvae (Hermetia illucens L.)

People are increasingly using black soldier fly larvae (BSFL) as a sustainable waste management solution. They are high in protein and other essential nutrients, making them an ideal food source for livestock, poultry, and fish. Prior laboratory studies with BSFL developed on pure mushroom root waste (MRW) showed poor conversion efficiency compared to a regular artificial diet. Therefore, we mixed the nutrient-rich soybean curd residues (SCR) with MRW in different ratios (M2-M5). Pure mushroom root waste (M1, MRW 100%) had the lowest survival rate (86.2%), but it increased up to 96.9% with the SCR percentage increasing. M1 had the longest developmental period (31.1 days) and the lowest BSFL weight (7.4 g). However, the addition of SCR reduced the development time to 22.0 and 21.5 days in M4 (MRW 40%, SCR 60%) and M5 (MRW 20%, SCR 80%), respectively, and improved the larval weight to 10.9 g in M4 and 11.8 g in M5. Other groups did not have as much feed conversion ratio (FCR) (8.4 for M4 and M5), bioconversion (M4 5.4%; M5 5.9%), or lipid content (M4 25.2%; M5 24.3%). These mixtures did. Compare this to M1. We observed better results, with no significant differences between the M4 and M5 groups and their parameters. In the present study, our main target was to utilize more MRW. Therefore, we preferred the M4 group in our nutritional and safety investigation and further compared it with the artificial diet (M7). The heavy metals and essential amino acids (histidine 3.6%, methionine 2.7%, and threonine 3.8%) required for human consumption compared to WHO/FAO levels showed satisfactory levels. Furthermore, fatty acids (capric acid 1.9%, palmitic acid 15.3%, oleic acid 17.3%, and arachidonic acid 0.3%) also showed higher levels in M4 than M7. The SEM images and FT-IR spectra from the residues showed that the BSFL in group M4 changed the structure of the compact fiber to crack and remove fibers, which made the co-conversion mixture better.

Vitamin E: An assistant for black soldier fly to reduce cadmium accumulation and toxicity

Cadmium (Cd) is a toxic heavy metal associated with osteoporosis, liver, and kidney disease. The black soldier fly (BSF) Hermetia illucens may be exposed to Cd during the transformation of livestock manure. The BSF has a high tolerance to Cd. In the previous work of the laboratory, we found that vitamin E (VE) may play a role in the tolerance of BSF to Cd exposure. The main findings are as follows: The BSF larvae pretreated with exogenous VE had heavier body weight, lower content and toxicity of Cd under similar Cd exposure. Even in high Cd exposure at the concentrations of 300 and 700 mg/kg, the BSF larvae pretreated with exogenous VE at a concentration of 100 mg/kg still reduced the Cd toxicity to 85.33 % and 84.43 %, respectively. The best-fitting models showed that metallothionein (MT) content, oxidative damage (8-hydroxydeoxyguanosine content, malondialdehyde content), antioxidant power (total antioxidant power, peroxidase activity) had a great influence on content and toxicity of Cd bioaccumulated in the larvae. The degree of oxidative damage was reduced in the larvae with exogenous VE pretreatments. This variation can be explained by their changed MT content and increased antioxidant power because of exogenous VE. These results reveal the roles of VE in insects defense against Cd exposure and provide a new option for the prevention and therapy of damage caused by Cd exposure.

Transforming food waste into animal feeds: an in-depth overview of conversion technologies and environmental benefits

Food waste is a global concern, with significant quantities of edible food being discarded every day. However, innovative conversion technologies have emerged to effectively transform this waste into valuable animal feed. This review paper provides a comprehensive examination of the conversion technologies used to transform food waste into animal feed, along with an analysis of the environmental benefits associated with these processes. The paper delves into various conversion methods such as anaerobic digestion, insect-based conversion, and microbial fermentation along with exploring their mechanisms and suitability for converting food waste into valuable animal feed resources. Additionally, the environmental benefits, including waste reduction, greenhouse gas emission reduction, and resource conservation, are discussed in detail. The review highlights the potential of these technologies to address the pressing issue of food waste while contributing to a more sustainable and resource-efficient food system. The findings of this review emphasize the importance of adopting and further developing these conversion technologies as a means to mitigate environmental impacts, promote circular economy principles, and enhance the overall sustainability of the food and agriculture sector.

Flight toward Sustainability in Poultry Nutrition with Black Soldier Fly Larvae

Black soldier fly larvae (BSFL), Hermetia illucens (L.) (Diptera: Stratiomyidae), have emerged as a promising feed ingredient in broiler chicken diets, known for their high protein content, nutritional richness, and environmental sustainability. This review examines the effects of integrating BSFL into broiler feeds, focusing on aspects such as growth performance, nutrient digestibility, physiological responses, and immune health. The ability of BSFL to transform waste into valuable biomass rich in proteins and lipids underscores their efficiency and ecological benefits. Protein levels in BSFL can range from 32% to 53%, varying with growth stage and diet, offering a robust source of amino acids essential for muscle development and growth in broilers. While the chitin in BSFL poses questions regarding digestibility, the overall impact on nutrient utilization is generally favorable. The inclusion of BSFL in diets has been shown to enhance growth rates, feed efficiency, and carcass quality in broilers, with the larvae's balanced amino acid profile being particularly advantageous for muscle development. BSFL may also support gut health and immunity in broilers due to its bioactive components, potentially influencing the gut's microbial composition and enhancing nutrient absorption and overall health. Moreover, the capacity of BSFL to efficiently convert organic waste into protein highlights their role as an environmentally sustainable protein source for broiler nutrition. Nonetheless, further research is necessary to fully understand the long-term effects of BSFL, ideal inclusion rates, and the impact of varying larval diets and rearing conditions. It is crucial for poultry producers to consult nutritionists and comply with local regulations when incorporating new feed ingredients like BSFL into poultry diets.

Effect of larval handling on black soldier fly life history traits and bioconversion efficiency

Introduction

The black soldier fly is considered the most promising insect species for mass production; however, information on the effects of handling, which is unavoidable during experimental trials and rearing practices, is still limited.

Materials and methods

To address this gap, three different manipulation intensities were tested on 100 6-day-old larvae per replica (6 replicates/treatments) fed on Gainesville diet: (1) hard-handled (HH), larvae underwent continuous manipulation until the end of larval stage, (2) soft-handled (SH), larvae were manipulated after the appearance of the first prepupa, (3) no-handled (NH), larvae remained untouched. Every 4 days from the beginning to the end of the larval stage, the manipulations lasted 30 min and occurred under laboratory conditions (20°C). During the sampling operations, at least 30 larvae were randomly extracted, washed, dried, and weight-mimicked. At the end of larval stage, all the boxes remained untouched until the adult fly stage, and the emergency rate and sex ratio were evaluated on dead flies. Data were statistically analyzed using IBM SPSS V20.0.0 software and the considered significance level was p < 0.05.

Results

The larval stage lasted 8.2 days for both HH and SH (p > 0.05). Despite the HH larvae being the most manipulated, no difference was also observed in final weight (HH, 160 mg; SH, 150 mg; p > 0.05) and survival rate (HH, 96.2%; SH, 94.5%; p > 0.05). The manipulation did not influence the bioconversion capacity of the larvae (bioconversion efficiency corrected for the residue: HH, 14.3%; SH, 12.91%; reduction rate: HH, 58.4%; SH, 55.9%; waste reduction index: HH, 7.28%/day; SH, 7.25%/day; p > 0.05). Finally, the development time from larva to fly (about 20.7; p > 0.05), the emergency rate (NH: 92.8%; SH: 89.5%; HH: 82.7%) and sex ratio (~1.2% to male flies) were not affected by the handling (p > 0.05).

Discussion

In conclusion, the handling procedures used in the current study did not influence the life history traits of the black soldier fly. However, further studies are needed to evaluate if different experimental protocols on various scales, the colony strain or other handling procedures may suggest a different scenario or confirm the results.

Synergistic bioconversion of organic waste by black soldier fly (Hermetia illucens) larvae and thermophilic cellulose-degrading bacteria

Introduction

This study examines the optimum conversion of Wuzhishan pig manure by Black Soldier Fly Larvae (BSFL) at various phases of development, as well as the impact of gut microbiota on conversion efficiency.

Method and results

In terms of conversion efficiency, BSFL outperformed the growing pig stage (GP) group, with significantly higher survival rates (96.75%), fresh weight (0.23 g), and larval conversion rate (19.96%) compared to the other groups. Notably, the GP group showed significant dry matter reductions (43.27%) and improved feed conversion rates (2.17). Nutritional composition varied, with the GP group having a lower organic carbon content. High throughput 16S rRNA sequencing revealed unique profiles, with the GP group exhibiting an excess of Lactobacillus and Clostridium. Promising cellulose-degrading bacteria in pig manure and BSFL intestines, including Bacillus cereus and Bacillus subtilis, showed superior cellulose degradation capabilities. The synergy of these thermophilic bacteria with BSFL greatly increased conversion efficiency. The BSFL1-10 group demonstrated high growth and conversion efficiency under specific conditions, with remarkable larval moisture content (71.11%), residual moisture content (63.20%), and waste reduction rate (42.28%).

Discussion

This study sheds light on the optimal stages for BSFL conversion of pig manure, gut microbiota dynamics, promising thermophilic cellulose-degrading bacteria, and the significant enhancement of efficiency through synergistic interactions. These findings hold great potential for sustainable waste management and efficient biomass conversion, contributing to environmental preservation and resource recovery.

Learning from the past to plan for the future: An historical review of the evolution of waste and resource management 1970-2020 and reflections on priorities 2020-2030 - The perspective of an involved witness

Improving waste and resource management (WaRM) around the world can halve the weight of plastics entering the oceans, significantly mitigate global heating and contribute directly to 12 of 17 sustainable development goals (SDGs). Achieving such results demands understanding and learning from historical evolution of WaRM. The baseline is 1970, prior to environmental legislation. Early steps in the Global North focused on the 'technical fix' within strictly enforced legal frameworks, first bringing hazardous wastes and municipal solid wastes (MSW) under control, then gradually ramping up environmental standards. Using modern technologies to the Global South often failed due to institutional and financial constraints. From 1990, focus switched to integrating technical and governance aspects: local institutional coherence, financial sustainability, provider inclusivity, user inclusivity, national legislative and policy framework. The Global North rediscovered recycling, using policy measures to promote segregation at source; this relied on new markets in emerging economies, which had largely disappeared by 2020. The Global South is making progress on bringing wastes under control, but around 2.7 billion people lack access to waste collection, while ~40% of collected MSW is open dumped or burned - a continuing global waste emergency. So, much remains to be done to move further towards a circular economy. Three policy priorities are critical for all countries: access to sustainable financing, rethinking sustainable recycling and worldwide extended producer responsibility with teeth. Extending services to unserved communities (SDG11.6.1) requires a people-centred approach, working with communities to provide both quality services and decent livelihoods for collection and recycling workers.

Optimization of Production Methods for Black Soldier Fly Larvae (Hermetia illucens L.) in Burkina Faso

Larvae of Hermetia illucens are a valuable source of protein for animal feed that can be produced by exposing animal and agro-industrial wastes to naturally occurring flies. The objective of this study was to improve techniques for obtaining H. illucens larvae to feed livestock in Burkina Faso. An experiment was conducted to determine the most favourable substrates and seasons for larval production. The substrates used were poultry manure, local beer waste, local beer waste mixed with poultry manure, cottonseed cake, and industrial brewery waste mixed with poultry manure. The production of larvae was carried out in four different seasons. The effect of the container's oviposition area (0.07 m2, 0.09 m2, and 0.11 m2) and the type of container (terracotta, plastic, and iron) on larval production was also assessed. The produced larval biomass was high during, or just after, the rainy season but very low during the cool dry and hot dry seasons. Yields were higher with local beer waste mixed with poultry manure followed by local beer waste and cottonseed cake. The average mass of H. illucens larvae increased slightly with the oviposition area for the same amount of substrate. Iron and terracotta containers provided better results than plastic containers. The suitability of this production method for H. illucens larvae production is discussed.

Effects of straw addition on the physicochemical and microbial features of black soldier fly larvae frass derived from fish meat and bone meal

Black soldier fly larvae (BSFL) hold great promise for sustainable management of meat and bone meal (MBM), a kind of organic waste. Harvested BSFL frass can be used as soil amendment or organic fertilizer. This study evaluated the quality and microbial profile in the frass of BSFL, fed with fish MBM containing 0% (CK), 1% (T1), 2% (T2) and 3% (T3) of rice straw. Results suggested straw addition into fish MBM had no significant impacts on BSFL weight; however, straw addition remarkably affected waste reduction and conversion efficiency, as well as physicochemical properties including electric conductivity, organic matter (OM) and total phosphorus contents in frass. Fourier transform infrared analysis indicated that increasing levels of cellulose and lignin might not be fully degraded or transformed by BSFL when more straw was introduced into substrates. Straw addition had hardly significant influences on microbial richness or evenness in BSFL frass, only T3 treatment remarkably elevated the phylogenetic diversity value more than the control. Bacteroidetes, Proteobacteria, Actinobacteria and Firmicutes were the most dominant phyla. Genera Myroides, Acinetobacter and Paenochrobactrum maintained high abundances in all frass samples. Elements including OM, pH and Na were key factors in shaping the microbiological characteristics of BSFL frass. Our findings helped to understand the effects of fish MBM waste manipulation on BSFL frass qualities and contributed to the further application of BSFL frass.

Microbiota is structured by gut regions, life stage, and diet in the Black Soldier Fly (Hermetia illucens)

The larvae of the Black Soldier Fly (Hermetia illucens) provide numerous ecological benefits, leading to significant commercial advancements. These benefits include the bioconversion of low-value waste into high-value feed and soil amendments. Understanding how the bacterial and eukaryotic microbiota communities affect host performance becomes vital for the optimization and specialization of industrial-scale rearing. This study investigates H. illucens-associated microbiota taxonomic composition and dynamics across the developmental cycle (eggs, neonates, larvae, prepupae, and imago X0 to second generation X1) when reared on two substrates: (i) plant-based (Housefly Gainesville diet) and (ii) animal-based (poultry hatchery waste). By using the 16S gene amplicon metataxonomic approach, we found that the results revealed that bacterial microbiota inherited from parents reared on a different substrate may have induced dysbiosis in the progeny. Specifically, the interaction networks of individuals reared on hatchery waste showed a high prevalence of negative interactions and low connectivity. Proteobacteria (39-92%), Firmicutes (4-39%), Bacteroidota (1-38%), and Actinobacteria (1-33%). In animal feed-reared individuals, Firmicutes reached the highest relative abundance (10-80%), followed by Proteobacteria (6-55%), Actinobacteria (1-31%), and Bacteroidota (0-22%). The rearing substrate was the main driver of microbiota composition, while the developmental stage influenced only the whole individual's bacterial microbiota composition. Gut regions were associated with distinct bacterial composition and richness, with diversity decreasing along the digestive tract. For the first time, microeukaryotes of the microbiota other than Fungi were investigated using 18S genetic marker amplicon sequencing with novel blocking primers specific to the Black Soldier Fly. Microeukaryotes are a neglected part of multitrophic microbiota communities that can have similar effects on their hosts as bacterial microbiota. Microeukaryotes from seven orders were identified in black soldier flies, including potential pathogens (e.g., Aplicomplexa group). Nucletmycea were the dominant class throughout development, followed by Holozoa and Stramenophiles. The eukaryote microbiota was structured by developmental stages but not by gut regions. Insights from this study are a stepping stone toward the microbiological optimization of black soldier flies for industrial rearing, highlighting how a synthetic microbiota assembly should be tailored to the rearing environment of the larvae at a targeted developmental stage.

Utilizing Black Soldier Fly Larvae to Improve Bioconversion and Reduce Pollution: A Sustainable Method for Efficient Treatment of Mixed Wastes of Wet Distiller Grains and Livestock Manure

Widespread environmental contamination caused by huge amounts of wastes generated by human activities has become a critical global concern that requires urgent action. The black soldier fly (BSFL) has gradually been used to treat different wastes due to high efficiency and low cost. However, little information is available regarding the treatment of mixed wastes by BSFLs. The impact of BSFLs on conversion of cow manure (COM) and pig manure (PM) via the incorporation of wet distiller grains (WDG) was assessed. Results demonstrate that the waste reduction rate was increased by 20% by incorporating 45% WDG to COM and PM. The bioconversion rate of BSFLs in COM and PM also increased from 1.20 ± 0.02% and 0.92 ± 0.02% to 10.54 ± 0.06% and 10.05 ± 0.11%, respectively. Total nitrogen content and δ15N/14N ratios of WDG + COM and WDG + PM were found to be significantly lower than those of COM and PM alone (p < 0.01). The organic matter changes during manure degradation were further analyzed by combing ultraviolet-visible spectrum (UV-vis) with excitation-emission matrix (EEM) spectroscopy techniques and fluorescence area integration (FRI) method. The UV-vis spectra results indicate that the addition of WDG to manures resulted in the decreased aromaticity and molecular weight of the waste. EEM spectra demonstrated that the accumulative Pi,n values of regions III and V in COM, COM + WDG, PM, and PM + WDG were 58%, 49%, 52% and 63%, respectively. These results not only provide new insights into the potential of mixed wastes for BSFL treatment but also contribute to the basis for the formulation of effective management measurements that reduce and/or reuse these wastes.

Feed nutritional composition affects the intestinal microbiota and digestive enzyme activity of black soldier fly larvae

Introduction

Using black soldier fly larvae (BSFLs) to treat food waste is one of the most promising environmental protection technologies.

Methods

We used high-throughput sequencing to study the effects of different nutritional compositions on the intestinal microbiota and digestive enzymes of BSF.

Results

Compared with standard feed (CK), high-protein feed (CAS), high-fat feed (OIL) and high-starch feed (STA) had different effects on the BSF intestinal microbiota. CAS significantly reduced the bacterial and fungal diversity in the BSF intestinal tract. At the genus level, CAS, OIL and STA decreased the Enterococcus abundance compared with CK, CAS increased the Lysinibacillus abundance, and OIL increased the Klebsiella, Acinetobacter and Bacillus abundances. Diutina, Issatchenkia and Candida were the dominant fungal genera in the BSFL gut. The relative abundance of Diutina in the CAS group was the highest, and that of Issatchenkia and Candida in the OIL group increased, while STA decreased the abundance of Diutina and increased that of Issatchenkia. The digestive enzyme activities differed among the four groups. The α-amylase, pepsin and lipase activities in the CK group were the highest, and those in the CAS group were the lowest or the second lowest. Correlation analysis of environmental factors showed a significant correlation between the intestinal microbiota composition and digestive enzyme activity, especially α-amylase activity, which was highly correlated with bacteria and fungi with high relative abundances. Moreover, the mortality rate of the CAS group was the highest, and that of the OIL group was the lowest.

Discussion

In summary, different nutritional compositions significantly affected the community structure of bacteria and fungi in the BSFL intestinal tract, affected digestive enzyme activity, and ultimately affected larval mortality. The high oil diet gave the best results in terms of growth, survival and intestinal microbiota diversity, although the digestive enzymes activities were not the highest.

Isolated and identified pathogenic bacteria from black soldier fly larvae with "soft rot" reared in mass production facilities and its incidence characteristics

The black soldier fly larvae (BSFL) can transform organic waste into high-end proteins, lipids, chitin, biodiesel, and melanin at an industrial scale. But scaling up of its production capacity has also posed health risks to the insect itself. In this investigation, larval "soft rot" which is occurring in mass production facilities that cause larval developmental inhibition and a certain degree of death was reported. Responsible pathogen GX6 was isolated from BSFL with "soft rot" and identified to be Paenibacillus thiaminolyticus. No obvious impact on larval growth was observed when treated with GX6 spores, whereas mortality of 6-day-old BSFL increased up to 29.33% ± 2.05% when GX6 vegetative cells (1 × 10⁶ cfu/g) were inoculated into the medium. Moreover, higher temperature further enhanced the BSFL mortality and suppressed larval development, but increasing substrate moisture showed the opposite effect. The middle intestine of infected larvae became swollen and transparent after dissection and examination. Transmission electron microscopy (TEM) observation indicated that GX6 had destroyed the peritrophic matrix and intestinal microvilli and damaged epithelial cells of larval gut. Furthermore, 16S rRNA gene sequencing analysis of intestinal samples revealed that gut microflora composition was significantly altered by GX6 infection as well. It can be noticed that Dysgonomonas, Morganella, Myroides, and Providencia bacteria became more numerous in the intestines of GX6-infected BSFL as compared to controls. This study will lay foundations for efficient control of "soft rot" and promote healthy development of the BSFL industry to contribute to organic waste management and circular economy.

An Acyl Carrier Protein Gene Affects Fatty Acid Synthesis and Growth of Hermetia illucens

Acyl carrier protein (ACP) is an acyl carrier in fatty acid synthesis and is an important cofactor of fatty acid synthetase. Little is known about ACP in insects and how this protein may modulate the composition and storage of fatty acids. We used an RNAi-assisted strategy to study the potential function of ACP in Hermetia illucens (Diptera: Stratiomyidae). We identified a HiACP gene with a cDNA length of 501 bp and a classical conserved region of DSLD. This gene was highly expressed in the egg and late larval instars and was most abundant in the midgut and fat bodies of larvae. Injection of dsACP significantly inhibited the expression level of HiACP and further regulated the fatty acid synthesis in treated H. illucens larvae. The composition of saturated fatty acids was reduced, and the percentage of unsaturated fatty acids (UFAs) was increased. After interfering with HiACP, the cumulative mortality of H. illucens increased to 68.00% (p < 0.05). H. illucens growth was greatly influenced. The development duration increased to 5.5 days, the average final body weights of larvae and pupae were decreased by 44.85 mg and 14.59 mg, respectively, and the average body lengths of larvae and pupae were significantly shortened by 3.09 mm and 3.82 mm, respectively. The adult eclosion rate and the oviposition of adult females were also severely influenced. These results demonstrated that HiACP regulates fatty acid content and influences multiple biological processes of H. illucens.

Effects of Disinfectants on Larval Growth and Gut Microbial Communities of Black Soldier Fly Larvae

The use of the black soldier fly has been demonstrated to be effective in the treatment of swine manure. Since the outbreaks of ASFV, prevention procedures, including manure disinfection, have changed dramatically. Glutaraldehyde (GA) and potassium peroxymonosulfate (PPMS) have been shown to be effective in the prevention of this pathogen and are thus widely used in the disinfection of swine manures, etc. However, research on the effects of disinfectants in manures on the growth of BSFL and gut microbiota is scarce. The goal of this study was to determine the effects of GA and PPMS on BSFL growth, manure reduction, and gut microbiota. In triplicate, 100 larvae were inoculated in 100 g of each type of manure compound (manure containing 1% GA treatment (GT1), manure containing 0.5% GA treatment (GT2), manure containing 1% PPMS treatment (PT1), manure containing 0.5% PPMS treatment (PT2), and manure without disinfectant (control)). After calculating the larval weight and waste reduction, the larval gut was extracted and used to determine the microbial composition. According to the results, the dry weights of the larvae fed PT1-2 (PT1: 86.7 ± 4.2 mg and PT2: 85.3 ± 1.3 mg) were significantly higher than those of the larvae fed GT1-2 (GT1: 72.5 ± 2.1 mg and GT2: 70 ± 2.8 mg) and the control (64.2 ± 5.8 mg). There was a 2.8-4.03% higher waste reduction in PT1-2 than in the control, and the waste reduction in GT1-2 was 7.17-7.87% lower than that in the control. In a gut microbiota analysis, two new genera (Fluviicola and Fusobacterium) were discovered in PT1-2 when compared to GT1-2 and the control. Furthermore, the disinfectants did not reduce the diversity of the microbial community; rather, Shannon indices revealed that the diversities of GT1-2 (GT1: 1.924 ± 0.015; GT2: 1.944 ± 0.016) and PT1 (1.861 ± 0.016) were higher than those of the control (1.738 ± 0.015). Finally, it was found that both disinfectants in swine manures at concentrations of 1% and 0.5% may be beneficial to the complexity and cooperation of BSFL gut microbiota, according to an analysis of microbial interactions.

Comparative Proteomic Analysis of Bacillus subtilis and Aspergillus niger in Black Soldier Fly Co-Fermentation

Black soldier fly larvae have gained popularity as an organic waste bio-conversional tool and fodder protein replacement in recent decades. It can consume all kinds of animal feces, kitchen waste and agricultural waste with great efficiency and transform them into high-value insect protein, fatty acids, and amino acids, which makes the larva a good substitute for costly fish meal and bean pulp in animal diets. However, excess chitin in the larva skin limits its application as an animal feed additive, consequently, employing fermentation with zymocytes to remove the chitin is necessary. In this study, we raised black soldier fly larvae (BSFL) with different carbon sources, such as chicken feces, straws and glucose, and examined the growth condition; we applied Bacillus subtilis and Aspergillus niger to co-ferment BSFL paste to analyze its nutrition changes. Data revealed that among the four kinds of cultures, the body weight of the corn powder group increased most rapidly; the wood chip group was the most underweight; however, it increased faster than others before day 4, and contained the least fat. Label-free quantitative proteomic analysis revealed that the expression of multiple enzymes from B. subtilis and A. niger involved in polysaccharide hydrolysis, amino acid biosynthesis and fatty acid metabolism, such as peptidase of S8 family, maltogenic α-amylase, oligo-1,6-glucosidase and lysophospholipase like protein changed significantly compared to the control group. Production detection showed that free amino acids, acid-soluble proteins, and short-chain fatty acids increased after fermentation; 13 out of 17 amino acids were increased and total free amino acids were increased from 0.08 g/100 g to 0.3 g/100 g; organic acids increased by 4.81 to 17 fold through fermentation, respectively; the actual protein content declined from 3.03 g/100 g to 1.81 g/100 g, the peptide content increased from 1.3 g/100 g to 2.46 g/100 g, the chitin degradation rate was 40.3%, and fat decreased 30% (p < 0.05). These findings might provide important information for future applications of black soldier fly larvae in different carbon waste recycling measures and material for animal feed/organic fertilizer after fermentation.

Nutritional Composition of Black Soldier Fly Larvae (Hermetia illucens L.) and Its Potential Uses as Alternative Protein Sources in Animal Diets: A Review

The rapidly growing population has increased demand for protein quantities and, following a shortage of plant-based feed protein sources and the prohibition of animal-based feed protein, has forced the search for new sources of protein. Therefore, humans have turned their attention to edible insects. Black soldier fly larvae (BSFL) (Hermetia illucens L.) are rich in nutrients such as fat, protein and high-quality amino acids and minerals, making them a good source of protein. Furthermore, BSFL are easily reared and propagated on any nutrient substrate such as plant residues, animal manure and waste, food scraps, agricultural byproducts, or straw. Although BSFL cannot completely replace soybean meal in poultry diets, supplementation of less than 20% has no negative impact on chicken growth performance, biochemical indicators and meat quality. In pig studies, although BSFL supplementation did not have any negative effect on growth performance and meat quality, the feed conversion ratio (FCR) was reduced. There is obviously less research on the feeding of BSFL in pigs than in poultry, particularly in relation to weaning piglets and fattening pigs; further research is needed on the supplementation level of sows. Moreover, it has not been found that BSFL are used in ruminants, and the next phase of research could therefore study them. The use of BSFL in animal feed presents some challenges in terms of cost, availability and legal and consumer acceptance. However, this should be considered in the context of the current shortage of protein feed and the nutritional value of BSFL, which has important research significance in animal production.