Review of Black Soldier Fly (Hermetia illucens) as Animal Feed and Human Food

Sericulture and the edible-insect industry can help humanity survive: insects are more than just bugs, food, or feed

The most serious threat which humans face is rapid global climate change, as the Earth shifts rapidly into a regime less hospitable to humans. To address the crisis caused by severe global climate change, it will be necessary to modify humankind's way of life. Because livestock production accounts for more than 14.5% of all greenhouse gas (GHG) emissions, it is critical to reduce the dependence of humans on protein nutrients and calories obtained from livestock. One way to do so is to use insects as food. Compared with typical livestock, farming edible insects (or "mini-livestock") produce fewer GHG emissions, require less space and water, involve shorter life cycles, and have higher feed conversion rates. It has been recently reported that consumption of certain insects can prevent or treat human diseases. This review goes beyond entomophagy to entomotherapy and their application to the food industry.

Isolation of Hermetia illucens larvae core gut microbiota by two different cultivation strategies

Hermetia illucens larvae (black soldier fly larvae, BSFL) convert efficiently organic waste to high quality biomass. To gain knowledge on the specific functions of gut microbes in this process it is a prerequisite to culture members of the core gut microbiota. Two different cultivation strategies were applied here for this purpose, a dilution-to-extinction cultivation and direct plating using six different media to culture aerobic heterotrophic bacteria. A total of 341 isolates were obtained by the dilution-to-extinction cultivation and 138 isolates by direct plating from guts of BSFL reared on chicken feed. Bacterial isolates were phylogenetically identified at the genus level by 16S rRNA gene sequencing (phylotyping) and differentiated at the strain level by genomic fingerprinting (genotyping). The main proportion of isolates was assigned to Proteobacteria, Firmicutes (Bacilli), and Actinobacteria. Predominant genera discussed in literature as member of a potential BSFL core gut microbiota, Providencia, Proteus, Morganella, Enterococcus, Bacillus, and members of the family Enterobacteriaceae, were isolated. A high intra-phylotype diversity was obtained by genomic fingerprinting which was especially enhanced by the dilution-to-extinction cultivation. This study showed that the application of different cultivation strategies including a dilution-to-extinction cultivation helps to culture a higher diversity of the BSFL gut microbiota and that genomic fingerprinting gives a better picture on the genetic diversity of cultured bacteria which cannot be covered by a 16S rRNA gene sequence based identification alone.

Characterization of chitin and chitosan derived from Hermetia illucens, a further step in a circular economy process

Due to their properties and applications, the growing demand for chitin and chitosan has stimulated the market to find more sustainable alternatives to the current commercial source (crustaceans). Bioconverter insects, such as Hermetia illucens, are the appropriate candidates, as chitin is a side stream of insect farms for feed applications. This is the first report on production and characterization of chitin and chitosan from different biomasses derived from H. illucens, valorizing the overproduced larvae in feed applications, the pupal exuviae and the dead adults. Pupal exuviae are the best biomass, both for chitin and chitosan yields and for their abundance and easy supply from insect farms. Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscope analysis revealed the similarity of insect-derived polymers to commercial ones in terms of purity and structural morphology, and therefore their suitability for industrial and biomedical applications. Its fibrillary nature makes H. illucens chitin suitable for producing fibrous manufacts after conversion to chitin nanofibrils, particularly adults-derived chitin, because of its high crystallinity. A great versatility emerged from the evaluation of the physicochemical properties of chitosan obtained from H. illucens, which presented a lower viscosity-average molecular weight and a high deacetylation degree, fostering its putative antimicrobial properties.

Replacing Dietary Fish Meal with Defatted Black Soldier Fly (Hermetia illucens) Larvae Meal Affected Growth, Digestive Physiology and Muscle Quality of Tongue Sole (Cynoglossus semilaevis)

For solving the global shortage of fish meal (FM) supplies from fisheries, the black soldier fly (Hermetia illucens) has become a new protein alternative in aquatic feeds. The present study investigated the effects of dietary inclusion of defatted H. illucens larvae meal (DBLM) on growth, serum biochemical parameters, digestive function, and muscle quality of tongue sole (Cynoglossus semilaevis). The feeding experiment consisted of five experimental diets: a control diet based on FM protein (H0) and four DBLM diets, substituting 25% (H25), 50% (H50), 75% (H75), and 100% (H100) of FM. C. semilaevis (initial weight 563.48 ± 22.81 g) were randomly allocated over five treatments in quadruplicate. After 65 days of feeding, the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) were significantly higher in H0 and H25 groups with less feed conversion ratio (FCR) and feed intake (FI). The concentrations of serum ALT, TG, T-CHO, ALB, and GLO and their ratio (i.e., A/G) in the H25 group were also significantly higher than those in the other DBLM diet-feeding groups. The digestive enzyme activities first increased (from 25% to 75%) and then decreased (from 75%) with the increased level of DBLM in diets. Meanwhile, there were significant improvements in the thickness of the intestinal longitudinal muscle (LM), circular muscle (CM), columnar epithelium (CE), and lamina propria (LP) in H25 C. semilaevis compared to the control group (p < 0.05). The fish from the other DBLM diets groups presented significant reductions in the thicknesses of LM, CM, CE, and LP, as well as the length of microvilli (ML) in a dose-dependent manner (p < 0.05). However, the substitution of FM increased up to 50% would result in intestinal structural damage. Moreover, the proximate compositions, antioxidant and water holding capacity, and muscular structures of C. semilaevis fillets were all significantly affected after substituting 25% FM with DBLM (p < 0.05). Except for the dry matter, moisture, ash, crude fat, and protein contents were significantly higher in H25 C. semilaevis muscles. The SOD activity in the H0 group was significantly lower than that in the H25 group. The CAT activity in C. semilaevis muscles prominently reduced along with the increase in DBLM content in feeding diets (p < 0.05). The water holding capacity of C. semilaevis fillets was best in the H25 group. In summary, the optimum proportion of DBLM with FM for feeding C. semilaevis may be around 25%.

A Review of Organic Waste Treatment Using Black Soldier Fly (Hermetia illucens)

The increase in solid waste generation is caused primarily by the global population growth that resulted in urban sprawl, economic development, and consumerism. Poor waste management has adverse impacts on the environment and human health. The recent years have seen increasing interest in using black soldier fly (BSF), Hermetia illucens, as an organic waste converter. Black soldier fly larvae (BSFL) feed voraciously on various types of organic waste, including food wastes, agro-industrial by-products, and chicken and dairy manure, and reduce the initial weight of the organic waste by about 50% in a shorter period than conventional composting. The main components of the BSFL system are the larvero, where the larvae feed and grow, and the fly house, where the adults BSF live and reproduce. It is essential to have a rearing facility that maintains the healthy adult and larval BSF to provide a sufficient and continuous supply of offspring for organic waste treatment. The BSF organic waste processing facility consists of waste pre-processing, BSFL biowaste treatment, the separation of BSFL from the process residue, and larvae and residue refinement into marketable products. BSFL digest the nutrients in the wastes and convert them into beneficial proteins and fats used to produce animal feed, and BSFL residue can be used as an organic fertilizer. This review summarizes the BSFL treatment process to provide an in-depth understanding of the value of its by-products as animal feed and organic fertilizer.

Dramatic effect of black soldier fly larvae on fungal community in a compost

BACKGROUND

Black soldier fly larvae (BSFL) offer very good prospects for the production of cheap and high-quality dietary protein. This insect is able to consume low-quality substrates, including food waste. The properties and safety of the compost obtained are largely determined by its microbiome. However, while the bacterial component of the BSFL-compost microbiome has been much studied, little is known about its fungal component. In plant-based rearing substrates both the biomass and the metabolic activity of fungi often exceed the biomass and the activity of prokaryotes. So, the purpose of this study was to investigate the fungal community of the compost produced by BSF larvae reared on a food waste substrate.

RESULTS

Community structure was determined by metabarcoding of the ITS (internal transcribed spacer) region. Species composition and abundance were determined using the plating technique and subsequent identification of the isolated pure cultures. It was found that the primary mycobiome of the food waste substrate that was used consisted of 19 families, represented mainly by phytopathogenic and endophytic genera. Larva incubation led to the complete elimination of all mycelial fungi from the resulting compost. The final mycobiome consisted of only two yeast species, Pichia kudriavzevii and Diutina rugosa, with a total abundance of 1.2 × 10⁷  CFU g^-1 .

CONCLUSIONS

The rearing of BSFL led to the complete elimination of mycelial fungi from its feed substrate. The final compost lacked harmful fungi, including molds. This information may be crucial for BSF compost utilization. The phenomenon was also an interesting aspect of zoomicrobial interactions in nature and agriculture. © 2021 Society of Chemical Industry.

Frass derived from black soldier fly larvae treatment of biodegradable wastes. A critical review and future perspectives

Inadequately treated biodegradable waste is considered an environmental, social and economic threat worldwide, which call for great attention. Waste treatment with larvae of the black soldier fly (BSF, Hermetia illucens) complies with the concepts of circular economy, as it enables the transformation of these wastes into marketable products, closing loops and promoting circularity. The processing residues of the treatment (frass) is constantly generated in waste management facilities in large volumes, and this product can be used as an organic fertilizer in agriculture, stimulating a transition to a circular economy. However, many aspects related to frass are still unknown, such as its varying composition of nutrients, microorganisms and bioactive compounds, its post-processing requirements for improved biological stabilization, its behavior in the soil and action in the plants' metabolism, among other aspects. In this review article, we highlight the potential of frass from BSF larvae treatment of biodegradable waste in the world market regarding its possible use as a fertilizer, summarize recent results with this novel product and point towards future research perspectives.

Effects of dietary black soldier fly (Hermetia illucens Linnaeus) on the disease resistance of juvenile grouper (Epinephelus coioides)

An experiment was performed to study the effects of dietary levels of black soldier fly larva meal (BSFLM) on the growth performance, immunity and disease resistance of juvenile grouper (Epinephelus coioides). Four isoproteic and isoenergetic diets were formulated with dietary BSFLM levels of 0 g/kg (T0), 25 g/kg (T2.5), 50 g/kg (T5) and 100 g/kg (T10). Each diet was randomly fed to triplicate groups, each containing 40 fish. The results of the 30-day study indicated that fish growth performance was not affected in the T2.5 and T5 groups compared with the T0 group. In the group with a dietary BSFLM level of 100 g/kg, the feed coefficient was significantly higher than that in the other three groups. The superoxide dismutase, catalase, glutathione peroxidase, lysozyme activity, and malondialdehyde content in the liver, and the interleukin-1 beta (IL-1β), gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α) and heat shock protein 70 (HSP70) expression in the gills, head kidney, liver and spleen remained consistent in all groups. In addition, no significant differences in the cumulative mortality or parasite abundance in groupers after Vibrio harveyi and Cryptocaryon irritans infection were observed. These results suggested that BSFLM supplemented diets did not inhibit disease resistance in groupers.

Growth of the Black Soldier Fly Hermetia illucens (Diptera: Stratiomyidae) on Organic-Waste Residues and Its Application as Supplementary Diet for Nile Tilapia Oreochromis niloticus (Perciformes: Cichlidae)

The black soldier fly, Hermetia illucens (BSF, Diptera: Stratiomyidae) is an insect with high protein value and a potential feed agent for animals aimed for human consumption. The growth parameters of BSF larvae reared on four substrates—restaurant-waste, fruit-waste, fish-waste, and commercial tilapia food—for 41 days before processing for inclusion into Oreochromis niloticus (Perciformes: Cichlidae, Nile tilapia) commercial fry diets at 30% (70:30) were determined. On fly larvae, the food substrate based on restaurant waste yielded the greatest larval weight and length. BSF larvae fed a fish-waste diet showed the shortest developmental time. The fruit-waste diet induced the lowest weight and length in the fly larvae/pre-pupae (immature stage). The pre-pupal protein values were similar to commercial food. On fry-fish, the diets with pre-pupae grown on fish waste showed the greatest yields regarding weight (biomass), length, and nutritional content. These results suggest the BSF has the potential to be used in fish feed and provides an alternative for commercial cultivation.

Metabolomic Effects of the Dietary Inclusion of Hermetia illucens Larva Meal in Tilapia

Black soldier fly (Hermetia illucens) larvae meal have been used as feed protein supplements in fish feed, but few researches have investigated the metabolomic effects of Hermetia illucens larvae meal supplements. Therefore, the metabolic effects on Nile tilapia were investigated by replacing 5%, 10%, and 20% of the dietary soybean meal in the basal diet with Hermetia illucens larvae meal, respectively. This study shows that 20% H. illucens larvae meal feed could promote tilapia average daily gain of upto 5.03 ± 0.18 g (mean ± SEM). It was found that the tricarboxylic acid cycle efficiency was improved by activating the enzymes of mitochondrial isocitrate dehydrogenase, NAD-malate dehydrogenase, succinate dehydrogenase, pyruvate dehydrogenase, and α-ketoglutarate dehydrogenase, which then increased the output of ATP and NADH. Furthermore, amino acid and protein biosynthesis was boosted by enhanced glutamine synthetase and glutamate synthase. In particular, GSH increased with increased H. illucens larvae meal. Unsaturated fatty acid biosynthesis was stimulated by higher levels of fatty acid synthase and acetyl CoA carboxylase. Additionally, there was no significant change in lipase levels. Thus, the higher acetyl Co-A content was primarily involved in fatty acid biosynthesis and energy metabolism. Flavor substances, such as nonanal and 2-methyl-3-furanthiol, also accumulated with the addition of H. illucens larvae meal, which increased the umami taste and meat flavor. Additionally, the flavor of tilapia was improved owing to a decrease in trimethylamine content, which causes an earthy and fishy taste. This study uncovers a previously unknown metabolic effect of dietary H. illucens larvae meal on Nile tilapia.

Evaluation of Antimicrobial Activity in the Extract of Defatted Hermetia illucens Fed Organic Waste Feed Containing Fermented Effective Microorganisms

Hermetia illucens (black soldier fly) larvae (HIL) are considered useful industrial insects for the production of feed for livestock, eco-friendly fertilizer from organic wastes, and biodiesel. Therefore, we evaluated the antimicrobial activity in the extract of crude-oil-extracted crushed HIL powder prepared from HIL fed organic waste containing fermented effective micro-organisms for biodiesel production. The result showed that antimicrobial activity was not fully induced in HIL fed L. casei-containing feed. In contrast, increased antimicrobial activity was observed in defatted HIL extract prepared from crude-oil-extracted crushed HIL powder. We found that the extract effectively inhibited the growth of pathogens and antimicrobial-peptide-resistant bacteria, such as three kinds of Salmonella species, and Enterococcus faecalis, Streptococcus mutans, Candida albicans, Serratia marcescens, and Pseudomonas tolaasii, with a minimum inhibitory concentration of 200-1000 µg/100 µL. Furthermore, no cytotoxicity to CaCO-2 human intestinal cells was observed in the extract. We also found that the production fee of extract equivalent to the antimicrobial activity of melittin was approximately 25-fold less than the production fee of melittin. Therefore, the results demonstrate that crude-oil-extracted crushed HIL powder prepared from HIL fed organic waste containing fermented effective micro-organisms for biodiesel production should be used as the feedstock for synthetic, preservative-free livestock feed and food additives. Taken together, the present study supports the usefulness of HIL as an eco-friendly feedstock in the biodiesel, agricultural, food, and feed industries.

Palatability and apparent total tract macronutrient digestibility of retorted black soldier fly larvae-containing diets and their effects on the fecal characteristics of cats consuming them

There is a growing interest in using black soldier fly larvae (BSFL) due to its supposed sustainability and nutritional qualities. Because little research has been conducted to evaluate the use of BSFL in cats, our objective was to determine the palatability and apparent total tract macronutrient digestibility (ATTD) of BSFL-containing canned diets and the fecal characteristics of healthy adult cats consuming them. First, three palatability tests were conducted to compare the following diets: 1) diet with poultry byproduct meal (PBPM) and chicken serving as the primary protein sources (control) vs. diet with BSFL meal replacing PBPM (BSFL meal); 2) control vs. diet with whole BSFL replacing some PBPM and poultry fat (BSFL whole); and 3) control vs. diet with BSFL oil replacing poultry fat (BSFL oil). All diets were formulated to meet Association of American Feed Control Officials nutrient profiles for adult cats and were produced using a still retort. A paired t-test was conducted to analyze data from each palatability test, with a higher (P < 0.05) consumption ratio being observed for BSFL meal (1.93:1), BSFL whole (2.03:1), and BSFL oil (1.57:1). Second, 32 adult cats (20 females and 12 males; BW: 4.19 ± 0.55 kg; age: 3.3 ± 0.38 yr) were used in a completely randomized design study composed of a 21-d baseline period and a 70-d experimental period. Cats consumed the control diet during the baseline and were then allotted to one of four experimental diets (n = 8 per group): 1) control, 2) BSFL meal, 3) whole BSFL, and 4) BSFL oil. Fecal samples were collected after baseline and experimental periods for ATTD and fecal characteristic analysis. Fecal output was higher (P < 0.05) and fecal dry matter percentage was lower (P < 0.05) in cats fed BSFL meal than those fed BSFL oil. Organic matter, crude protein (CP), and energy ATTD were lower (P < 0.05) in cats fed BSFL meal than those fed BSFL oil or control. CP and energy ATTD were lower (P < 0.05) in cats fed BSFL whole than those fed BSFL oil. A few serum metabolites were affected by diet (P < 0.05) but remained within reference ranges. Hematology was not affected by diet (P > 0.05). Overall, our results suggest that BSFL-containing diets are palatable and do not negatively affect fecal characteristics or serum chemistry but may have slightly lower nutrient digestibilities in adult cats.

A sustainable and economic strategy to reduce risk antibiotic resistance genes during poultry manure bioconversion by black soldier fly Hermetia illucens larvae: Larval density adjustment

Black soldier fly (Hermetia illucens) larvae (BSFL) are common insects that are known for bioconversion of organic waste into a sustainable utilization resource. However, a strategy to increase antibiotic resistance gene (ARG) elimination in sustainable and economic ways through BSFL is lacking. In the present study, different larval densities were employed to assess the mcr-1 and tetX elimination abilities, and potential mechanisms were investigated. The application and economic value of each larval density were also analyzed. The results showed that the 100 larvae cultured in 100 g of manure group had the best density because the comprehensive disadvantage evaluation ratio was the lowest (14.97%, good bioconversion manure quality, low ARG deposition risk and reasonable larvae input cost). Further investigation showed that mcr-1 could be significantly decreased by BSFL bioconversion (4.42 ×10⁷ copies/g reduced to 4.79 ×10⁶-2.14 ×10⁵ copies/g)(P＜0.05); however, mcr-1 was increasingly deposited in the larval gut with increasing larval density. The tetX abundance was stabilized by BSFL bioconversion, except that the abundance at the lowest larval density increased (1.22 ×10¹⁰ copies/g increase, 34-fold). Escherichia was the host of mcr-1 and tetX in all samples, especially in fresh manure; Alcaligenes was the host of tetX in bioconversion manure; and the abundance of Alcaligenes was highly correlated with the pH of bioconversion manure. The pH of bioconversion manure was extremely correlated with the density of larvae. Klebsiella and Providencia were both hosts of tetX in the BSF larval gut, and Providencia was also the host of mcr-1 in the BSF larval gut. The density of larvae influenced the bioconversion manure quality and caused the ARG host abundance to change to control the abundance of ARGs, suggesting that larval density adjustment was a useful strategy to manage the ARG risk during BSFL manure bioconversion.

Black soldier fly larvae (BSFL) and their affinity for organic waste processing

There are two major problems that we are facing currently. Firstly, a growing human population continues to contribute to the increased food demand. Secondly, the volume of organic waste produced will threaten human health and the quality of the environment. Recently, there is an increasing number of efforts placed into farming insect biomass to produce alternative feed ingredients. Black soldier fly larvae (BSFL), Hermetia illucens have proven to convert organic waste into high-quality nutrients for pet foods, fish and poultry feeds, as well as residue fertilizer for soil amendment. However, better BSFL feed formulation and feeding approaches are necessary for yielding a higher nutrient content of the insect body, and if performed efficiently, whilst converting waste into higher value biomass. Lastly, this paper reveals that BSFL, in fact, thrives in various ranges of organic matter composition and with simple rearing systems.

Nutritional, Techno-Functional and Structural Properties of Black Soldier Fly (Hermetia illucens) Larvae Flours and Protein Concentrates

Due to their protein content and balanced amino acid profile, edible insects have been described as an excellent alternative protein source to combat malnutrition. As the global population continues to grow, edible insects such as the black soldier fly larvae (BSFL) may contribute to food security. The effect of different protein extraction methods, i.e., alkaline solution and acid precipitation (BSFL-PC1) and extraction with an alkali (BSFL-PC2), on the nutritional, techno-functional, and structural properties of BSFL flours and protein concentrates were studied. The highest protein content (73.35%) was obtained under alkaline and acid precipitation extraction (BSFL-PC1). The sum of essential amino acids significantly increased (p < 0.05) from 24.98% to 38.20% due to the defatting process during extraction. Protein solubility was significantly higher in protein concentrates (85−97%) than flours (30−35%) at pH 2. The emulsion capacity (EC) was significantly higher (p < 0.05) in the protein concentrates (BSFL-PC1 and BSFL-PC2) compared to the freeze-dried and defatted BSFL flours, while the emulsion stability (ES) was significantly (p < 0.05) higher in BSFL-PC1 (100%) compared with BSFL-PC2 (49.8%). No significant differences (p > 0.05) were observed in foaming stability (FS) between freeze-dried and defatted BSFL flours. Fourier transform infrared spectroscopy (FT-IR) analysis revealed distinct structural differences between BSFL flours and protein concentrates. This was supported by surface morphology through scanning electron microscopy (SEM) images, which showed that the protein extraction method influenced the structural properties of the protein concentrates. Therefore, based on the nutritional and techno-functional properties, BSFL flour fractions and protein concentrates show promise as novel functional ingredients for use in food applications.

Effect of Dietary Meat Content on Weight Gain, Mortality, and Pre-Pupal Rate in Black Soldier Fly (Hermetia illucens) Larvae

Simple Summary

Recently, using insects to process food waste has attracted much attention from researchers. In this study, we investigated the extent to which meat can be included in the diets of immature black soldier flies. Based on our results, it was found that the meat content should be less than 80%. In addition, previous studies have shown that the protein and fat content of immature black soldier fly diets are important for growth and survival. However, it became clear in the present study that it is necessary to pay more attention to the nitrogen-free extract content of a diet than to the protein and fat content.

Abstract

This study aimed to determine the protein content and the ratio of meat that can be added to the diet of black soldier fly (BSF) larvae for the sustainable recycling of food waste using insects. We conducted experiments feeding refined diets to BSF larvae with adjusted protein content and diets with minced pork, and analyzed the correlations between dietary nutrients and larval weight gain, mortality, and pre-pupal rate. The nutrient that was positively correlated with increased larval body weight and pre-pupal rate in both experiments was nitrogen-free extract (NFE). Diets with high concentrations of minced pork showed higher mortality of BSF larvae and were negatively correlated with dietary NFE content. It has been suggested that BSF larvae have reduced body weight and survival due to excessive protein and fat in their diet. Depending on the raw material and ratio of food waste, it may be necessary to adjust dietary protein and fat contents before treatment. The results of this study suggest that the NFE content of a larval diet influences the larval weight gain, mortality, and pre-pupal rate of BSF larvae in a great extent, a finding that has not been reported by previous studies.

Nutritional value of black soldier fly (Hermetia illucens) larvae processed by different methods

Nutritional value of black soldier fly (Hermetia illucens) larvae (BSFL) processed by three different methods of treatment was compared. The resulting products were the spray-dried BSFL (SPR), oven-dried BSFL 1 (OVN1) and oven-dried BSFL 2 (OVN2). Proximate chemical composition, and profiles of amino acids, fatty acids, minerals, heavy metals, vitamins and nucleotides were analysed and compared. The tested BSFL meals were considered to have a good profile of essential amino acids (EAAs), with leucine, lysine, valine, and histidine being the dominant EAAs. Their content of saturated fatty acids exceeded that of the unsaturated fatty acids. Vitamins B1, B2, and C were also present in the samples. Minerals such as calcium, potassium, phosphorus, sodium, magnesium, zinc, iron, manganese and copper were found to be in adequate amounts in almost all the samples. Heavy metals in the BSFL meals were mostly below 1g kg^-1. Nucleotides such as inosine monophosphate and uridine monophosphate occurred in all the BSFL meals. Other nucleotides, including guanosine monophosphate, adenosine monophosphate, xanthosine monophosphate, and cytidine monophosphate were detected in either or both of SPR and OVN2. In general, the nutritional value of the BSFL meals tested in the present study was influenced by the method of processing.

Odorant binding proteins fromHermetia illucens: potential sensing elements for detecting volatile aldehydes involved in early stages of organic decomposition

Organic decomposition processes, involving the breakdown of complex molecules such as carbohydrates, proteins and fats, release small chemicals known as volatile organic compounds (VOCs), smelly even at very low concentrations, but not all readily detectable by vertebrates. Many of these compounds are instead detected by insects, mostly by saprophytic species, for which long-range orientation towards organic decomposition matter is crucial. In the present work the detection of aldehydes, as an important measure of lipid oxidation, has been possible exploiting the molecular machinery underlying odour recognition inHermetia illucens(Diptera: Stratiomyidae). This voracious scavenger insect is of interest due to its outstanding capacity in bioconversion of organic waste, colonizing very diverse environments due to the ability of sensing a wide range of chemical compounds that influence the choice of substrates for ovideposition. A variety of soluble odorant binding proteins (OBPs) that may function as carriers of hydrophobic molecules from the air-water interface in the antenna of the insect to the receptors were identified, characterised and expressed. An OBP-based nanobiosensor prototype was realized using selected OBPs as sensing layers for the development of an array of quartz crystal microbalances (QCMs) for vapour phase detection of selected compounds at room temperature. QCMs coated with four recombinantH. illucensOBPs (HillOBPs) were exposed to a wide range of VOCs indicative of organic decomposition, showing a high sensitivity for the detection of three chemical compounds belonging to the class of aldehydes and one short-chain fatty acid. The possibility of using biomolecules capable of binding small ligands as reversible gas sensors has been confirmed, greatly expanding the state-of the-art in gas sensing technology.

Isolation of Bacterial and Fungal Microbiota Associated with Hermetia illucens Larvae Reveals Novel Insights into Entomopathogenicity

Larvae of the black soldier fly (BSF) Hermetia illucens are polyphagous feeders and show tremendous bioconversion capabilities of organic matter into high-quality insect biomass. However, the digestion of lignocellulose-rich palm oil side streams such as palm kernel meal (PKM) is a particular challenge, as these compounds are exceptionally stable and are mainly degraded by microbes. This study aimed to investigate the suitability of BSF larvae as bioconversion agents of PKM. Since the intestinal microbiota is considered to play a key role in dietary breakdown and in increasing digestibility, the bacterial and fungal communities of BSF larvae were characterized in a culture-dependent approach and screened for their putative entomopathogenicity. The lethality of six putative candidates was investigated using intracoelomal injection. In total, 93 isolates were obtained with a bacterial share of 74% that were assigned to the four phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. Members of the genera Klebsiella, Enterococcus, and Sphingobacterium are part of the core microbiome, as they were frequently described in the gut of Hermetia larvae regardless of diet, nutritional composition, or rearing conditions. With 75%, a majority of the fungal isolates belonged to the phylum Ascomycota. We identified several taxa already published to be able to degrade lignocelluloses, including Enterococcus, Cellulomonas, Pichia yeasts, or filamentous Fusarium species. The injection assays revealed pronounced differences in pathogenicity against the larvae. While Alcaligenes faecalis caused no, Diutina rugosa weak (23.3%), Microbacterium thalassium moderate (53.3%), and Pseudomonas aeruginosa and Klebsiella pneumoniae high (≥80%) lethality, Fusarium solani injection resulted in 100% lethality.

Recognizing Potential Pathways to Increasing the Consumption of Edible Insects from the Perspective of Consumer Acceptance: Case Study from Finland

Mitigating the sustainability challenges related to agriculture and ensuring adequate availability of nutritious food requires an increase in the use of sustainable alternative protein sources. Edible insects are considered to be a sustainable protein source and a possible substitute for meat. There are many readily available edible insect species with many competing utilization possibilities, which, from the producers’ perspective, increases the complexity of the area. Through a consumer survey and expert interviews, this study recognizes four pathways to increasing the use of edible insects in Western countries and especially in Finland where the survey and interviews were conducted: (1) producing a variety of insect-based food products, especially food products where insects are not recognizable as such and the food is in a familiar form; (2) producing edible insect food products which could replace greenhouse gas emission-intensive animal proteins; (3) focusing on the price, taste, and availability of insect food; and (4) using insects as animal feed. Our findings provide information on the prospects of the studied pathways in terms of consumption and production. Technological development is expected to decrease the price of insect-based food products, but at the same time, the increased use of edible insects faces challenges related to eating habits, contradictory perceptions about the sustainability implications of insect farming, and the availability of insect-based products.

Evaluation of Black Soldier Fly larvae (Hermetia illucens) as a protein supplement for beef steers consuming low-quality forage

Black Soldier Fly larvae (BSFL; Hermetia illucens) has been the focus of recent feeding trials in poultry, swine, and fish; however, in vivo research has not yet been conducted in cattle. Accordingly, a study was conducted to evaluate the effects of BSFL as a protein supplement in beef steers. Six steers (603 ± 20 kg of BW, n = 3 and 404 ± 17 kg of BW, n = 3) consuming King Ranch bluestem hay (6.55% dry matter [DM] crude protein [CP]) ad libitum were used in two simultaneous 3 × 3 Latin squares. Steers were provided one of three treatments each period: 1) a control with no supplement (CON), 2) a supplement comprised of conventional feed ingredients with whole cottonseed and soybean meal as the main protein sources (CONV), and 3) a supplement with BSFL as the main protein source (BSFL). Three 14-d periods were conducted with 8 d to adapt to treatments, 5 d to measure intake and digestion, and 1 d to complete a ruminal fermentation profile. DM, organic matter (OM), CP, neutral detergent fiber (NDF), and acid detergent insoluble ash were determined in forage, supplement, ort, and fecal samples. Protein supplementation as CONV or BSFL stimulated forage OM intake (P ≤ 0.01) relative to CON with a trend for a difference (P = 0.08) between the supplements such that CONV steers consumed more FOMI than BSFL steers. Treatment affected total digestible OM intake (TDOMI; P ≤ 0.01); TDOMI for CON steers was 47.5 g/kg metabolic body weight (MBW) which was significantly less (P ≤ 0.01) than that of CONV or BSFL steers. Steers supplemented with CONV consumed significantly more TDOMI than BSFL steers (P = 0.05; 62.2 vs. 60.1 g/kg MBW, respectively). Treatment did not significantly affect digestibility of DM, OM, or NDF (P > 0.32). There was also not a significant effect (P ≥ 0.17) of treatment on ruminal ammonia-N, total volatile fatty acids, or ruminal pH. Overall, these data indicate that BSFL may be an effective protein supplement for beef cattle consuming low-quality forage.

Do It by Yourself: Larval Locomotion in the Black Soldier Fly Hermetia illucens, with a Novel “Self-Harvesting” Method to Separate Prepupae

Simple Summary

The black soldier fly Hermetia illucens is a widespread species of fly of American origins, which is increasingly used to develop sustainable waste recycling processes as it is able to develop by consuming a wide variety of wastes as food, while both its body and the residuals of its feeding activity can be re-used in a variety of processes. However, many aspects of its larval biology remain unknown. Among these, there is larval movement and its variation in response to external stimuli and environmental conditions. Larvae of the black soldier fly eventually reach the prepupal stage, during which they stop feeding and seek a shelter to pupate. Sorting prepupae from the younger larvae and feeding substratum can be important in rearing processes, since they are used to obtain adults but are also particularly rich in protein and lipids. We focused our study on behavioural differences between prepupae and younger larvae, describing tonic immobility as an anti-predatory response of both, but also their very different ways of locomotion and reactions to stress. Finally, we developed a practical system to exploit these differences, inducing prepupae to move away from the substratum and other larvae to be efficiently collected.

Abstract

The neotropical insect Hermetia illucens has become a cosmopolite species, and it is considered a highly promising insect in circular and sustainable economic processes. Being able to feed on a wide variety of organic substrates, it represents a source of lipids and proteins for many uses and produces recyclable waste. We investigated the characteristics and differences in the poorly-known locomotory behaviour of larvae of different instars, paying particular attention to the unique characteristics of the prepupal stage, key to farming and industrial processes. Moreover, we attempted to develop a “self-harvesting” system relying on the behavioural traits of prepupae to obtain their separation from younger larvae under rearing condition with minimum effort. Prepupae differ from younger larvae in their response to physical disturbance in the form of tonic immobility and significantly differ in their locomotory movements. Both prepupae and younger larvae reacted similarly to heat or light-induced stress, but low light and high moisture induced only prepupae to migrate away, which resulted in the development of a highly efficient separation methodology. The new data on the behaviour of H. illucens not only shed new light on some unexplored aspects of its biology, but also led to develop an inexpensive self-harvesting system that can be implemented in small-scale and industrial farming.

Meat Quality of Guinea Pig (Cavia porcellus) Fed with Black Soldier Fly Larvae Meal (Hermetia illucens) as a Protein Source

The most widely used feed ingredients in the world are fishmeal and soybean, which, despite having high-quality digestible protein and good fat content, are considered environmentally unsustainable and increasingly expensive. This issue also involves the guinea pig, a very important animal protein source for people in Andean regions in South America. Here we investigate the substitution of soybean meal with 50% and 100% black soldier fly larvae meal in the guinea pig diet and its effects on meat quality (fatty acid profile, amino acid profile, water-holding capacity, pH, proximal composition, and color). The results showed no differences in the protein content and amino acid profile of meat nor in the n-6:n-3 and P/S ratios, but did show an increment in the desirable fats (mono- and polyunsaturated fatty acids) in the guinea pigs fed with black soldier fly larvae meal. All the other analyzed parameters showed no differences among the diets tested. These results suggest that total replacement of soybean meal with black soldier fly larvae meal in guinea pig nutrition is feasible since meat quality was maintained or improved.

Isoenergetic-practical and semi-purified diets for protein requirement determination in Hermetia illucens larvae: consequences on life history traits

Background

Black soldier fly (BSF) is one of the most promising species for the intensive breeding of insects given its adaptability and its efficiency in the conversion of waste. To maximize the production and use waste as substrates, it is essential to determine the larvae nutritional requirements. The study aims to evaluate the effects of 5 practical, semi-purified and isoenergetic diets (PSPID) with increasing protein levels (10%, CP10; 14%, CP14; 16%, CP16; 19%, CP19) on BSF life history traits. A total of 2000 six-day-old larvae were weighed and divided into groups of 100 (4 replicates/treatment [PSPID and Gainesville diet (GA) used as environmental control]). In larva-prepupa stage, sampling was carried out on 30 individuals/replicate, while in prepupa-adult stage on 35.

Results

In the whole larval stage, the CP16 treatment performed better when compared to the other groups. At 18 days old, the CP14 treatment showed a higher weight than the CP19 (P < 0.01), while the CP10 and CP16 weights were intermediate. On the contrary, the CP10 prepupae weight was higher than the CP19 (P < 0.01). The CP10 and CP14 pupae performed better in terms of weight when compared to the others (P < 0.01). The dietary treatments did not affect the adult parameters. The sex significantly influenced both the exuvia weight, which was the greatest in females (P < 0.001), and the fly lifespan, longest in males (P < 0.05). Fly lifespan was also influenced by the interaction between treatment and sex, with the CP19 females showing a longer life than the others (P < 0.05).

Conclusions

In conclusion, the optimal protein level considering the whole larval stage is 16% on dry matter (DM). At 18 days old, looking at the size intended for the meal production, it can be considered 14% on DM. The result obtained on adult emergence in PSPID may not be attributable to the protein content. Further researches on macronutrients requirements determination have to be conducted to evaluate the substrates composition effects on BSF life history traits.

Dietary Hermetia illucens Larvae Meal Improves Growth Performance and Intestinal Barrier Function of Weaned Pigs Under the Environment of Enterotoxigenic Escherichia coli K88

The aim of this study was to evaluate the effect of Hermetia illucens larvae meal (HI) on the growth performance and intestinal barrier function of weaned pigs. To achieve this, 72 weaned pigs [28-day-old, 8.44 ± 0.04 kg body weight (BW)] were randomly assigned to three dietary treatments: basal diet (negative control, NC), zinc oxide-supplemented diet (positive control, PC), and HI-supplemented diet [100% replacement of fishmeal (FM), HI], for 28 days in the presence of enterotoxigenic Escherichia coli (ETEC). The results showed that HI and PC increased (p < 0.05) the average daily gain (ADG) and average daily feed intake (ADFI) of weaned pigs from day 1 to 14, and decreased diarrhea incidence from day 1 to 28. Additionally, HI increased (p < 0.05) claudin-1, occludin, mucin-1 (MUC-1), and MUC-2 expression, goblet cell number, and secretory immunoglobulin A (sIgA) concentration in the intestine of weaned pigs. Compared with NC, HI downregulated (p < 0.05) interleukin-1β (IL-1β) and IL-8 expression, and upregulated IL-10, transforming growth factor-β (TGF-β), antimicrobial peptide [porcine β defensin 1 (pBD1), pBD2, protegrin 1-5 (PG1-5)] expression in the jejunum or ileum. Moreover, HI decreased (p < 0.05) toll-like receptor 2 (TLR2), phosphorylated nuclear factor-κB (p-NF-κB), and phosphorylated mitogen-activated protein kinase (p-MAPK) expression, and increased sirtuin 1 (SIRT1) expression in the ileum. Additionally, HI increased histone deacetylase 3 (HDAC3) expression and acetylation of histone 3 lysine 27 (acH3k27) in the ileum. Furthermore, HI positively influenced the intestinal microbiota composition and diversity of weaned pigs and increased (p < 0.05) butyrate and valerate concentrations. Overall, dietary HI improved growth performance and intestinal barrier function, as well as regulated histone acetylation and TLR2-NF-κB/MAPK signaling pathways in weaned pigs.

A Combination of Hermetia illucens Reared on Fish Waste and Poultry By-Product Meal Improves Sensory and Physicochemical Quality of Farmed Barramundi Filets

The proximate composition, sensory attributes, and shelf life of filets from barramundi, Lates calcarifer, were fed a fishmeal (FM) based diet (0PBM-0HI) and three test diets replacing FM protein entirely with 85% poultry by-products meal (PBM) and 15% Hermetia illucens (HI) larvae meal protein (85PBM-15HI), 80% PBM and 20% HI (80PBM-20HI) and 75% PBM and 25% HI (75PBM-25HI) were investigated. After a 56-day feeding trial, the crude protein, moisture, and ash percentage were unchanged while the crude lipid increased in barramundi filet when fed with PBM-HI-based diets. The increase in C12:0 (lauric acid) and C14:0 (myristic acid) resulted in an increase in the total saturated fatty acid while the monounsaturated fatty acid elevated due to an increase in C16:1n7 and C18:1cis + trans in the filet of the barramundi fed with a PBM-HI based diet. While the decrease in the total polyunsaturated fatty acid (PUFA) content in PBM-HI based fed barramundi filet was mainly due to a decrease in essential fatty acids including C20:5n3 [eicosapentaenoic acid (EPA)] and C22:6n3 [docosahexaenoic acid (DHA)] when compared with the 0PBM-0HI fed barramundi filet. The sensory quality was improved by PBM-HI-based diets, manifested by the highest scores given by the panelists. Texture profiles were not affected by diet but cohesiveness, gumminess, and chewiness decreased with increasing storage time. On days 1 and 8, skin brightness decreased in the skin of the barramundi fed with 85PBM-15HI and 80PBM-20HI compared with the skin of the 0PBM-0HI fed barramundi. Skin redness improved in fish-fed PBM-HI-based diets. The flesh brightness and yellowness increased significantly in barramundi when fed with PBM-HI-based diets. On days 1 and 4, the flesh brightness of the barramundi fed with PBM-HI-based diets demonstrated an increase compared with 0PBM-0HI. PBM-HI diets suppress lipid oxidation while lipid oxidation increased over the storage time. In summary, the improvement in sensory quality and color coupled with the suppression of rancidity in barramundi filets underpinned the potentiality of using the mixture of PBM and HI transformed from food waste in the barramundi diet to improve the filet quality and thus support sustainability and circular economy in aquaculture.

Understanding dietary carbohydrates in black soldier fly larvae treatment of organic waste in the circular economy

Black soldier fly larvae (BSFL) treatment is promising for organic waste valorisation in the circular economy; however, waste variability impacts the process performance and quality of produced larvae. Specifically, variation in the carbohydrate profile of treated wastes has been suggested to have a significant impact on BSFL treatment performance and quality of produced larvae, with particular carbohydrates either positively or negatively influencing these variables. This study examines the hypothesis that the types of carbohydrates within the substrate can have significant influence on larval survival, waste reduction, bioconversion, and waste conversion efficiency, as well as the crude lipid content and fatty acid profiles of the produced larvae. The carbohydrates explored were D glucose, sucrose, D (-) fructose, corn and wheat starch, D (+) galactose, D (+) mannose, D (+) xylose, D (-) arabinose and xylan from beechwood. Young larvae were grown for 9 days on chicken feed-based diets containing various carbohydrate additives each at 20 dry mass %. Treatments containing hemicellulose constituents galactose and arabinose produced the most adverse effects on process performance relative to the benchmark. Xylan was significantly detrimental to bioconversion (-14.7 ± 3.8%) and waste conversion efficiencies (-19.0 ± 4.4%). There were minimal significant effects on performance from mono- and di-saccharides and starch additives. Larvae crude lipid contents were significantly increased by wheat starch (+12.6 ± 3.0%) and decreased by galactose (-15.0 ± 1.4%) and xylan additives (-27.5 ± 3.4%), however fatty acid profiles were largely unaffected and were dominated by lauric acid. These results indicate that despite an otherwise balanced and nutritious substrate, the carbohydrate profile of organic waste should be an important consideration in BSFL treatment when ensuring process performance and larval lipid contents. The consequences of these results for BSFL treatment of real wastes are discussed. Large scale treatment facilities should formulate substrates accordingly and identify methods to mitigate the anti-nutritional effects of poor carbohydrate profiles, particularly those high in hemicelluloses and their constituents.

Conversion of Mixtures of Soybean Curd Residue and Kitchen Waste by Black Soldier Fly Larvae (Hermetia illucens L.)

The production of insect biomass from organic waste is a major challenge in terms of reducing the environmental impacts of waste and maintaining feed and food security. The feasibility of the co-conversion of soybean curd residue (SCR) and kitchen waste (KW) to breed black soldier fly (BSF, Hermetia illucens) larvae was evaluated so as to enhance biomass conversion efficiency and supply animal feed and allow it to be used in biodiesel production. Co-digestion was found to significantly increase larval yield, bioconversion rate, and bioaccumulation of lipid. Partial least squares regression showed that the conversion of 30% SCR with 70% KW is an appropriate proportion. The appropriate performance parameters of BSF were: survival rate (98.75%), prepupal rate (88.61%), larval biomass (30.32 g fresh and 11.38 g dry mass), bioconversion rate (18.45%), efficiency conversion of ingested food (ECI) (28.30%), and FCR (2.51). Our results show that conversion of mixtures (e.g., SCR with KW) by BSF larvae (BSFL) could play an important role in various organic materials management.

The metabolism and role of free fatty acids in key physiological processes in insects of medical, veterinary and forensic importance

Insects are the most widespread group of organisms and more than one million species have been described. These animals have significant ecological functions, for example they are pollinators of many types of plants. However, they also have direct influence on human life in different manners. They have high medical and veterinary significance, stemming from their role as vectors of disease and infection of wounds and necrotic tissue; they are also plant pests, parasitoids and predators whose activities can influence agriculture. In addition, their use in medical treatments, such as maggot therapy of gangrene and wounds, has grown considerably. They also have many uses in forensic science to determine the minimum post-mortem interval and provide valuable information about the movement of the body, cause of the death, drug use, or poisoning. It has also been proposed that they may be used as model organisms to replace mammal systems in research. The present review describes the role of free fatty acids (FFAs) in key physiological processes in insects. By focusing on insects of medical, veterinary significance, we have limited our description of the physiological processes to those most important from the point of view of insect control; the study examines their effects on insect reproduction and resistance to the adverse effects of abiotic (low temperature) and biotic (pathogens) factors.

Evaluation of Fermented Oat and Black Soldier Fly Larva as Food Ingredients in Senior Dog Diets

Simple Summary

Along with concerns about the shortage of future food resources, the problem of ensuring a stable supply of feed materials is emerging. The rapid growth of the pet food market is also increasing the demand for new food ingredients, requiring the evaluation of their safety and nutritional value. Recently, insects and fermented foods are some of the materials that have entered the spotlight as potential future foods, and studies on their usefulness as food are being actively conducted. This study aimed to evaluate and verify the safety of fermented oat (Avena sativa) and black soldier fly larva (Hermetia illucens L.) when used in a dog food as part of the effort toward discovering suitable nutritionally excellent and functional food materials. Our results show that 10% fermented oat flour, 5% black soldier fly larva meal, or a combination thereof in the food did not negatively affect food intake, body weight, fecal status, skin condition, or hematological and biochemical parameters. Overall, our findings suggest that fermented oat and black soldier fly larva can be used as food ingredients for dogs.

Abstract

The aim of this study was to evaluate the suitability of fermented oat (FO) and black soldier fly larva (BSFL) as food ingredients for dogs. A total of 20 spayed female dogs were divided into four treatment groups, with 5 dogs per group. The four treatment groups consisted of a control group, a diet with 10% FO, one with 5% BSFL, and one with 10% FO and 5% BSFL, and each experimental food was fed for 12 weeks. The feeding of FO and/or BSFL did not affect the daily food intake, body weight, body condition score, fecal score, or skin condition of the dogs. In all the experimental groups, no significant differences in serum IgG, IL-10, or TNF-α levels were observed upon the feeding of FO and/or BSFL. Some hematological (white blood cell and basophils) and serum biochemical parameters (phosphorous, globulin, and alkaline phosphatase) showed significant differences with FO and/or BSFL feeding compared to the control group, but they were within the normal reference range. No adverse clinical signs related to these parameters being affected by FO and BSFL were observed. The feeding of BSFL for 12 weeks reduced the serum cholesterol level (p < 0.05) at the end of the experiment. Our findings suggest the suitability of FO and BSFL as food materials for dogs.

Predicting black soldier fly larvae biomass and methionine accumulation using a kinetic model for batch cultivation and improving system performance using semi-batch cultivation

Global demand for poultry and associated feed are projected to double over the next 30 years. Insect meal is a sustainable alternative to traditional feeds when produced on low-value high-volume agricultural byproducts. Black soldier fly (BSF) larvae (Hermetia illucens L.) are high in protein and contain methionine, an essential amino acid that is critical to poultry health. BSF larvae can be grown on many organic residues, however, larvae growth and quality vary based on feedstock and cultivation processes. Experiments were completed to monitor temporal changes in BSF larvae growth and composition using almond hulls as a growth substrate under batch and semi-batch processes and with varying substrate carbon to nitrogen ratio (C/N). A logistic kinetic growth model was developed to predict larval biomass and methionine accumulations during batch production. Estimated ranges of model parameters for larvae maximum specific growth rate and carrying capacity were 0.017–0.021 h⁻¹ and 9.7–10.7 g larvae kg⁻¹ hulls dry weight, respectively. Methionine content in larvae increased from 11.1 to 17.1 g kg⁻¹ dry weight over a 30-day batch incubation period. Larvae-specific growth and yield increased by 168% and 268%, respectively, when cultivated in a semi-batch compared to a batch process. Increasing C/N ratio from 26 to 40 increased density of methionine content in larvae per unit feedstock by 25%. The findings demonstrate a logistic model can predict larvae biomass accumulation, harvest time can achieve specific methionine contents, and a semi-batch process is more favorable for larvae biomass accumulation compared to a batch process.

Habitat-centric versus species-centric approaches to edible insects for food and feed

The current paradigm of the edible insects for food and feed industry uses a species-centric approach in which an insect species is chosen first and development of rearing practices follows. The goal is to optimize production to maximize the yield of that species in that facility. In contrast, the habitat-centric approach first chooses a habitat, either natural or artificial, then develops harvesting or rearing protocols within that habitat. The goal of this approach is to maximize the yield derived from that habitat. The habitat-centric approach eliminates potential threats from invasive species, and can repurpose local food and agricultural waste into protein derived from local insect species. This approach can increase food security by increasing the diversity of insects that are mass-produced. The species-centric and habitat-centric approaches address different issues and offer advantages in different situations. Further development of the edible insect industry will likely use a combination of both approaches.

Growth of Black Soldier Fly Larvae Reared on Organic Side-Streams

Black soldier fly (BSF) larvae may play a role in a circular economy by upcycling low-value organic streams into high value biomass. In this paper, the capacity of BSF larvae to process 12 organic side-streams (mono-streams) and two standard substrates (chicken start mash and Gainesville diet) was investigated. Survival, larval mass, feed conversion ratio, and waste reduction were evaluated in relation to the proximate composition of the side-streams used. Survival rates larger than 80% were observed for 10 of the organic mono-streams and the two standard substrates. Maximum mean larval weight ranged from 38.3 mg up to 176.4 mg regardless of high survival and was highly correlated with substrate crude protein content. Feed conversion ratio (range 1.58–8.90) and waste reduction (range 17.0–58.9%) were similar to values reported in other studies in the literature. On low protein substrates (e.g., apple pulp), survival rates remained high, however, possibly due to protein deficiency, limited larval growth was observed. It is concluded that several low value organic side-streams can successfully be processed by BSF larvae, thereby opening the possibility of lowering the costs of BSF farming. Potentially mixing nutritionally distinct mono-streams into a mixed substrate might improve BSF performance. However, more research is needed for optimizing diets to guarantee production of BSF larvae of constant yield and quality.

Digestibility of insect meals for Pacific white shrimp (Litopenaeus vannamei) and their performance for growth, feed utilization and immune responses

This study was conducted to examine digestibility of insect meals for Pacific white shrimp (Litopenaeus vannamei) and their utilization as fish meal substitutes. The tested insect meals were mealworm, silkworm, black soldier fly, rice grasshopper, two-spotted cricket, dynastid beetle and white-spotted flower chafer. Apparent digestibility coefficients of the tested insect meals were 83-89% for protein, 91-98% for lipid, 84-90% for energy, 77-81% for dry matter, 28-36% for chitin, 76-96% for amino acids and 89-93% for fatty acids. The amino acid availability of insect meals was high in taurine (93-96%), arginine (91-95%) and lysine (90-95%). Availability of fatty acids were 89-93% for saturated fatty acids, 90-93% for monounsaturated fatty acids and 88-93% for polyunsaturated fatty acids. For a feeding trial, a control diet was formulated using 27% tuna byproduct meal as a fish meal source and seven other diets were prepared replacing 10% tuna byproduct meal in the control diet with each insect meal. Triplicate groups of shrimp (initial body weight: 0.17 g) were fed the diets for 65 days. The growth performance was significantly improved when the shrimp were fed black soldier fly or dynastid beetle included diet. Dietary supplementation of insect meals significantly improved non-specific immune responses and antioxidant enzyme activity in the shrimp. These results indicate that the tested insect meals have high potentials to be used as a protein source that could replace fish meal in diets for the shrimp.

Biomass and Cordycepin Production by the Medicinal Mushroom Cordyceps militaris-A Review of Various Aspects and Recent Trends towards the Exploitation of a Valuable Fungus

Cordyceps militaris is an entomopathogenic ascomycete with similar pharmacological importance to that of the wild caterpillar fungus Ophiocordyceps sinensis. C. militaris has attracted significant research and commercial interest due to its content in bioactive compounds beneficial to human health and the relative ease of cultivation under laboratory conditions. However, room for improvement exists in the commercial-scale cultivation of C. militaris and concerns issues principally related to appropriate strain selection, genetic degeneration of cultures, and substrate optimization. In particular, culture degeneration-usually expressed by abnormal fruit body formation and reduced sporulation-results in important economic losses and is holding back investors and potential growers (mainly in Western countries) from further developing this highly promising sector. In the present review, the main factors that influence the generation of biomass and metabolites (with emphasis on cordycepin biosynthesis) by C. militaris are presented and evaluated in conjunction with the use of a wide range of supplements or additives towards the enhancement of fungal productivity in large-scale cultivation processes. Moreover, physiological and genetic factors that increase or reduce the manifestation of strain degeneration in C. militaris are outlined. Finally, methodologies for developing protocols to be used in C. militaris functional biology studies are discussed.

A Systematic Review on Viruses in Mass-Reared Edible Insect Species

Edible insects are expected to become an important nutrient source for animals and humans in the Western world in the near future. Only a few studies on viruses in edible insects with potential for industrial rearing have been published and concern only some edible insect species. Viral pathogens that can infect insects could be non-pathogenic, or pathogenic to the insects themselves, or to humans and animals. The objective of this systematic review is to provide an overview of the viruses detected in edible insects currently considered for use in food and/or feed in the European Union or appropriate for mass rearing, and to collect information on clinical symptoms in insects and on the vector role of insects themselves. Many different virus species have been detected in edible insect species showing promise for mass production systems. These viruses could be a risk for mass insect rearing systems causing acute high mortality, a drastic decline in growth in juvenile stages and in the reproductive performance of adults. Furthermore, some viruses could pose a risk to human and animal health where insects are used for food and feed.

Nature-Based Units as Building Blocks for Resource Recovery Systems in Cities

Cities are producers of high quantities of secondary liquid and solid streams that are still poorly utilized within urban systems. In order to tackle this issue, there has been an ever-growing push for more efficient resource management and waste prevention in urban areas, following the concept of a circular economy. This review paper provides a characterization of urban solid and liquid resource flows (including water, nutrients, metals, potential energy, and organics), which pass through selected nature-based solutions (NBS) and supporting units (SU), expanding on that characterization through the study of existing cases. In particular, this paper presents the currently implemented NBS units for resource recovery, the applicable solid and liquid urban waste streams and the SU dedicated to increasing the quality and minimizing hazards of specific streams at the source level (e.g., concentrated fertilizers, disinfected recovered products). The recovery efficiency of systems, where NBS and SU are combined, operated at a micro- or meso-scale and applied at technology readiness levels higher than 5, is reviewed. The importance of collection and transport infrastructure, treatment and recovery technology, and (urban) agricultural or urban green reuse on the quantity and quality of input and output materials are discussed, also regarding the current main circularity and application challenges.

Black Soldier Fly (Hermetia illucens) Larvae Meal Modulates Intestinal Morphology and Microbiota in Xuefeng Black-Bone Chickens

The addition of Hermetia illucens larvae meal (HILM) to the feed could contribute to particular antimicrobial and intestinal health in animal husbandry. This study was conducted to investigate the effects of HILM on intestinal morphology and microbial diversity in different intestinal segments of Xuefeng black-bone chickens. All of 432 birds (45 weeks old) were randomly assigned to four equal groups with six replicates and 18 hens in each replicate: (A) basal diet, (B) basal diet with 1% HILM, (C) basal diet with 3% HILM, and (D) basal diet with 5% HILM. The results showed that, compared with the basal diet group, the HILM supplement significantly increased the abundance-based coverage estimator (ACE) and Chao index in cecum (p < 0.05). Diet with 1% HILM significantly increased the villus height (VH) of the duodenum (p < 0.05) and cecum microbial diversity as represented by the Simpson index (p < 0.05). In particular, 1% HILM displayed a markedly increase in the genus unclassified Bacteroidales (cecum, p < 0.05). A basal diet with 3% HILM markedly increased the beneficial genus Romboutsia (jejunum, p < 0.05). Also, principal component analysis (PCA) cluster analysis showed that 3% of HILM was more individual than other groups (p < 0.05). However, 5% HILM decreased the VH and the ratio of villus height to crypt depth (VH/CD) of the jejunum and increased beneficial bacteria such as Staphylococcus (p < 0.05), which was regarded as pathogenetic genera. In conclusion, we found that HILM improved intestinal morphology and increased microbiological diversity and species abundance. Together, dietary supplementation of 1 or 3% HILM might benefit the intestinal morphology and intestinal microbiota of Xuefeng black-bone chicken. However, the addition of 5% HILM could decrease VH and the ratio of VH/CD of the jejunum and increased pathogenetic genera. HILM was an excellent protein substitute for Xuefeng black-bone chickens, which could meet the nutritional requirements under the condition of less feed. These results provide information for HILM meal as an alternative source of soybean meal in Xuefeng black-bone chickens’ feed.

A Molecular Survey of Bacterial Species in the Guts of Black Soldier Fly Larvae (Hermetia illucens) Reared on Two Urban Organic Waste Streams in Kenya

Globally, the expansion of livestock and fisheries production is severely constrained due to the increasing costs and ecological footprint of feed constituents. The utilization of black soldier fly (BSF) as an alternative protein ingredient to fishmeal and soybean in animal feed has been widely documented. The black soldier fly larvae (BSFL) used are known to voraciously feed and grow in contaminated organic wastes. Thus, several concerns about their safety for inclusion into animal feed remain largely unaddressed. This study evaluated both culture-dependent sequence-based and 16S rDNA amplification analysis to isolate and identify bacterial species associated with BSFL fed on chicken manure (CM) and kitchen waste (KW). The bacteria species from the CM and KW were also isolated and investigated. Results from the culture-dependent isolation strategies revealed that Providencia sp. was the most dominant bacterial species detected from the guts of BSFL reared on CM and KW. Morganella sp. and Brevibacterium sp. were detected in CM, while Staphylococcus sp. and Bordetella sp. were specific to KW. However, metagenomic studies showed that Providencia and Bordetella were the dominant genera observed in BSFL gut and processed waste substrates. Pseudomonas and Comamonas were recorded in the raw waste substrates. The diversity of bacterial genera recorded from the fresh rearing substrates was significantly higher compared to the diversity observed in the gut of the BSFL and BSF frass (leftovers of the rearing substrates). These findings demonstrate that the presence and abundance of microbiota in BSFL and their associated waste vary considerably. However, the presence of clinically pathogenic strains of bacteria in the gut of BSFL fed both substrates highlight the biosafety risk of potential vertical transmission that might occur, if appropriate pre-and-postharvest measures are not enforced.

Hermetia illucens (L.) (Diptera: Stratiomyidae) Odorant Binding Proteins and Their Interactions with Selected Volatile Organic Compounds: An In Silico Approach

The black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae), has considerable global interest due to its outstanding capacity in bioconverting organic waste to insect biomass, which can be used for livestock, poultry, and aquaculture feed. Mass production of this insect in colonies requires the development of methods concentrating oviposition in specific collection devices, while the mass production of larvae and disposing of waste may require substrates that are more palatable and more attractive to the insects. In insects, chemoreception plays an essential role throughout their life cycle, responding to an array of chemical, biological and environmental signals to locate and select food, mates, oviposition sites and avoid predators. To interpret these signals, insects use an arsenal of molecular components, including small proteins called odorant binding proteins (OBPs). Next generation sequencing was used to identify genes involved in chemoreception during the larval and adult stage of BSF, with particular attention to OBPs. The analysis of the de novo adult and larval transcriptome led to the identification of 27 and 31 OBPs for adults and larvae, respectively. Among these OBPs, 15 were common in larval and adult transcriptomes and the tertiary structures of 8 selected OBPs were modelled. In silico docking of ligands confirms the potential interaction with VOCs of interest. Starting from the information about the growth performance of H. illucens on different organic substrates from the agri-food sector, the present work demonstrates a possible correlation between a pool of selected VOCs, emitted by those substrates that are attractive for H. illucens females when searching for oviposition sites, as well as phagostimulants for larvae. The binding affinities between OBPs and selected ligands calculated by in silico modelling may indicate a correlation among OBPs, VOCs and behavioural preferences that will be the basis for further analysis.

Effect of Feed Containing Hermetia illucens Larvae Immunized by Lactobacillus plantarum Injection on the Growth and Immunity of Rainbow Trout (Oncorhynchus mykiss)

Simple Summary

In this study, we evaluated the effect on the growth and immunity of rainbow trout of a feed formulated using Hermetia illucens with increased antimicrobial peptides expression by Lactobacillus plantarum infection (ImHIL). As a result, growth and immunological indicators improved, and therefore, ImHIL is expected to become a good feed source for rainbow trout aquaculture.

Abstract

We investigated the effects of a feed containing Hermetia illucens larvae injected with bacteria on the growth and immunity of Oncorhynchus mykiss. The feed was prepared by replacing fishmeal in feed with 25 and 50% nonimmunized (HIL25, HIL50) or immunized HIL (ImHIL25, ImHIL50), and its protein:fat:carbohydrate ratio was 45:15:18. ImHIL extracts showed inhibitory activity against fish pathogenic bacteria. Both red blood cell count and insulin-like growth factor-1 as the growth indicator were the highest among the groups at week 6 after feeding in the ImHIL50 group. As immune indicators, blood aspartate aminotransferase levels were lower in the ImHIL25 and ImHIL50 groups than in that of other groups at week 6 after feeding, and lysozyme content was significantly higher in ImHIL25 and ImHIL50. The above results demonstrate that ImHIL has a beneficial effect on the improvement of growth and immunity. Accordingly, we suggest that ImHIL has the potential to be a good feed source in aquaculture.

Effect of Defatting and Extraction Solvent on the Antioxidant and Pancreatic Lipase Inhibitory Activities of Extracts from Hermetia illucens and Tenebrio molitor

Simple Summary

The food industry is notably investing more resources on the production of nutritious, healthy, safe and sustainable products derived from edible insects. In this sense, natural extracts (or concentrated forms of compounds from natural sources) are usually food ingredients with added value for human health. This is due to their intrinsic beneficious biological activities; however, bioactive extracts from edible insects have been scarcely explored. Due to that and considering that the bioactivities of extracts might be conditioned by parameters of the technological process, we assessed how different extraction conditions, such as the defatting of the raw insect flours or the extraction solvents employed, affected two bioactivities of the resulting extracts from insects: the blocking of the digestion of fats from the diet by evaluating the inhibition of the responsible enzyme (pancreatic lipase), as well as their antioxidant activity. T. molitor and H. illucens were used, as they are two of the most known edible species for both feed and food. We observed a multibioactivity for all the extracts. Both tested processing factors differentially modulated the bioactivity of extracts from both species. We also analysed the composition of the H. illucens extracts and detected amino acids, lipids, carbohydrates, sterols and organic acids.

Abstract

The production of specific insect extracts with bioactive properties for human health is an emerging and innovative field for the edible insects industry, but there are unexplored extraction factors that might modulate the bioactivity of the extracts. Ultrasound-assisted extracts from T. molitor and H. illucens were produced. Effects of defatting pre-treatment and extraction solvent were evaluated on extraction yield, antioxidant activity and pancreatic lipase inhibitory effect. Chemical characterisation of defatted extracts from H. illucens was performed by GC-MS-FID. Non-defatted extracts showed higher extraction yields. Defatted extracts had similar extraction yields (around 3%). Defatted extracts had higher antioxidant activity, T. molitor being stronger than H. illucens. Antioxidant activity of T. molitor methanol extract was higher than the rest of solvents. Aqueous ethanol improved the antioxidant activity of H. illucens extracts. All extracts inhibited lipase, but no significant effect of defatting and solvent was observed for T. molitor. A significant higher inhibitory activity was observed for H. illucens, the strongest being defatted 100% and 70% ethanol H. illucens extracts. H. illucens extracts contained free amino acids and disaccharides, together with minor fractions of lipids, sterols and organic acids. These results evidence the potential of extracts obtained from edible insects as antioxidants and inhibitors of the pancreatic lipase, a simultaneous multibioactivity that might be favoured by the defatting pre-treatment of the samples and the solvent of extraction.

Comparative Lipid Profile Analysis of Hermetia illucens Larvae Fed Food Waste at Different Days of Age Using an LC-MS-Based Lipidomics Approach

A lipidomics approach based on liquid chromatography-tandem mass spectrometry (LC-MS) was applied to analyze the molecular-level mechanism of lipid deposition in Hermetia illucens (H. illucens) larvae fed food waste (FW) at different days of age. The H. illucens larvae reared on FW substrates generally became larger, heavier, and fatter at 5-15 d of age. A large amount of glycerolipids (GL) were deposited, while glycerophospholipids (GP), sphingolipids, and derivatized lipids became relatively less abundant during the growth stage of the larvae. Forty-three subclasses of 3,205 lipid molecules were identified in larvae, and 139 lipids (79 upregulated and 60 downregulated during larval growth and development) were identified as potential biomarkers (variable importance in projection > 1; P < 0.05). The differential lipids were mainly enriched in 19 metabolic pathways, of which 9 metabolic pathways related to lipids, including GL and GP metabolisms. The results demonstrate that the lipid composition and mechanisms changed during the growth and development stage of H. illucens larvae. To the best of our knowledge, this is the first work exploring the molecular-level mechanism of lipid deposition during the growth and development stage of H. illucens larvae. The findings provide novel information for determining and utilizing the nutritional value of H. illucens larvae.

Optimization of Feed Components to Improve Hermetia illucens Growth and Development of Oil Extractor to Produce Biodiesel

Simple Summary

This investigation was performed to establish an optimal feed for Hermetia illucens (black soldier fly) larvae (HIL) and to develop an oil extractor for biodiesel production. An optimal feed for HIL for biodiesel production was established using organic wastes such as dried-food waste, chicken manure, and waste cooking oil. In addition, an automatic oil extractor was developed that cost-effectively produced industrial biodiesel, livestock feed, and fertilizer from HIL. Consequently, this investigation can contribute to the establishment of industrial systems for biodiesel production using HIL.

Abstract

HIL are useful in agriculture because they can be used as feed for livestock or fertilizer and can bioconvert organic wastes, such as food waste and human and animal manure to usable fertilizer. In addition, HIL are being studied as a source of biodiesel because of their high-fat content. However, their use for biodiesel production has not been fully adopted. Here, the results showed that survival, weight gains, and total dried weight were significantly enhanced when HIL were fed dried-food waste (DFW)/chicken manure (CM). Furthermore, increased weight gain was observed in HIL fed DFW containing 5 mL waste cooking oil (WCO) per 100 g and 1.2% (v/w) fermented effective microorganism (F-EM). Based on these results, we prepared experimental feeds containing DFW, CM, WCO, and F-EM to establish an optimal feed for biodiesel production. We found that FT-1-2, a feed prepared with 60 g DFW, 40 g CM, 2 mL WCO, and 0.8% F-EM (v/w), significantly enhanced fat content, weight gain, and total dried weight of HIL. Our results indicate FT-1-2 is a suitable feed to breed HIL for biodiesel production. We then developed an automatic oil extractor for biodiesel production. The yield of the oil extractor was higher than that of solvent extraction. The study shows FT-1-2 is an optimal HIL feed for biodiesel production and that the developed oil extractor is useful for the extraction of crude oil from HIL and for the harvesting of defatted HIL frass for livestock feed and fertilizer. Taken together, we established an optimized low-cost feed for HIL breeding and developed an automatic oil extractor for the production of biodiesel from HIL.