Mealworm (Tenebrio molitor): Potential and Challenges to Promote Circular Economy

Effects of Organic Xenobiotics on Tenebrio molitor Larvae and Their Parasite Gregarina polymorpha

Environmental contamination with xenobiotics affects organisms and the symbiotic relations between them. A convenient object to study relationships between parasites and their hosts is the host-parasite system "Tenebrio molitor Linnaeus, 1758 (Coleoptera, Tenebrionidae)-Gregarina polymorpha (Hammerschmidt, 1838) Stein, 1848 (Eugregarinorida, Gregarinidae)". For this experiment, we took 390 T. molitor larvae and 24 organic compounds. Groups of mealworms, 15 in each, were subjected to those compounds for 10 days. Then, we recorded the vitality of both the larvae of T. molitor and G. polymorpha. To assess how G. polymorpha had affected the hosts' wellbeing, we looked for changes in the larvae's body mass and compared them to the number of gregarines in their intestines. The vitality of the larvae was inhibited by cyclopentanol and 2-naphthol. The intensity of gregarine invasion was reduced by diphenyl ether, benzyl alcohol, catechol, and 3-aminobenzoic acid. No effect on the number of gregarines was produced by 3,4,5-trihydroxybenzoic acid, cyclohexanemethanol, phenol, benzalkonium chloride, maleic anhydride, cyclohexanol, resorcin, benzoic acid, 2-methylfuran, terpinen-4-ol, 1-phenylethylamine, dibutyl phthalate, 3-furancarboxylic acid, 5-methyl furfural, 6-aminohexanoic acid, succinic anhydride, o-xylene, and benzaldehyde. In the infected T. molitor individuals, the mean number of G. polymorpha equaled 45 specimens per host. The groups of smaller mealworms had fewer gregarines. Positive correlation was seen between growth rates of T. molitor larvae and the intensity of invasion by gregarines.

Insects as a Prospective Source of Biologically Active Molecules and Pharmaceuticals-Biochemical Properties and Cell Toxicity of Tenebrio molitor and Zophobas morio Cell-Free Larval Hemolymph

Insects are of great interest as novel sources of alternative proteins and biologically active compounds, primarily anticancer agents. Protein-rich insect larval hemolymph is a prospective candidate for pharmaceutical and food industry-related research. In this study, selected biochemical properties and cell toxicity of larval hemolymph from two mealworm species, Tenebrio molitor and Zophobas morio, were analyzed. Total proteins and carbohydrates, antioxidant capacity, and the level of lipid peroxidation were determined. Human cancer (U-87) and normometabolic (MRC-5) cells were treated with different concentrations of larval hemolymph proteins, and the effects on cell viability were assayed 24, 48, and 72 h after treatments. Z. morio hemolymph was shown to be richer in total proteins, showing a higher antioxidant capacity and lipid peroxidation level than T. molitor hemolymph, which was richer in total carbohydrates. Cytotoxicity assays showed that T. molitor and Z. morio hemolymphs differently affect the viability of U-87 and MRC-5 cells in cell type-, dose-, and time-dependent manners. Hemolymph from both species was more cytotoxic to U-87 cells than to MRC-5 cells, which was particularly prominent after 48 h. Additionally, a more potent cytotoxic effect of Z. morio hemolymph was observed on both cell lines, likely due to its higher antioxidant capacity, compared to T. molitor hemolymph.

Sub-chronic toxicity determination of powdered Tenebrio molitor larvae as a novel food source

Tenebrio molitor larvae are the first insect species to be given a favorable assessment by the European Food Safety Authority (EFSA) as a novel food source, enabling consumption of whole insect larvae or larvae that have been powdered and processed into a variety of food products. Pressure from economic hardships and increase in population growth have paved a way for the realization of an alternative food source in Zimbabwe. This study focused on determining the potential toxicity of Tenebrio molitor larvae powder as an alternative food source for humans. To determine the sub-chronic toxicity of Tenebrio molitor, the powder was administered daily by oral gavage to Sprague-Dawley rats at dose levels of 0, 300, 1000 and 3000 mg/kg for 70 days. A toxicological assessment which included mortality, appearance of clinical symptoms, food consumption, organ and body weight changes were performed. There were no treatment-related mortalities, clinical signs, changes in food consumption, body and organ weights observed during the treatment period. The study's findings suggest Tenebrio molitor larvae to be a good alternative as it did not appear to affect the rats' normal physiological and metabolic processes hence can be considered safe for human consumption. However, further studies on hematological, histological and biochemical markers may be necessary for confirmation of these current results.

Sourcing chitin from exoskeleton of Tenebrio molitor fed with polystyrene or plastic kitchen wrap

In this work we have characterized and compared chitin sourced from exoskeleton of Tenebrio molitor larvae fed with polystyrene or plastic kitchen wrap combined with bran in the ratio 1: 1 with chitin sourced from larvae exoskeleton fed only with bran. Analysis of the frass by ATR-FTIR showed very similar spectra and confirmed degradation of the plastic feed components, while ATR-FTIR analysis of the exoskeleton verified the absence of any plastic residue. Deproteinization followed by demineralization produced 6.78-5.29 % chitin, showing that plastic (polystyrene or plastic kitchen wrap) in the larvae diet resulted in heavier insect exoskeleton, but yielded slightly less chitin, with the lowest value obtained for plastic kitchen wrap in the insect diet. The deacetylation degree of 98.17-98.61 % was determined from measured ATR-FTIR spectra. XRD analysis confirmed the presence of α-chitin with a crystallinity index of 66.5-62 % and crystallite size 4-5 nm. Thermogravimetric analysis showed similar degradation curves for all chitin samples, with two degradation steps. These results show that chitin sourced from exoskeleton of T. molitor larvae fed with plastic (polystyrene or plastic kitchen wrap) and contributing to significant biodegradation of major polluting materials can be a feasible and alternative source of chitin, further promoting a bio-circular economy.

Exploiting Agri-Food Waste as Feed for Tenebrio molitor Larvae Rearing: A Review

The agri-food industry generates substantial amounts of waste, including by-products and residues. The increasing demand for sustainable and eco-friendly practices in the agri-food sector has sparked an interest in finding alternative uses for such waste materials. One promising approach is the utilization of waste from the agri-food industry as feed for the rearing of mealworms (Tenebrio molitor). Since agri-food waste is rich in proteins, carbohydrates, lipids, and vitamins, as well as other bioactive compounds, all of which are essential for insect growth and development, incorporating such waste into the diet of mealworms promotes sustainable insect production, reducing the economic and environmental problems associated with waste disposal. This practice can also be beneficial for the rearing of mealworms since their nutritional value can also be enhanced. To this end, various waste materials, such as fruit and vegetable peels, spent grains, and food processing residues, have been investigated as potential feed sources, leading to increased mass production, lower cost, and enhanced nutritional value. This review aims to highlight the potential of agri-food waste as a feed source for mealworms, as well as their potential to enhance their nutritional value. Furthermore, the potential applications of mealworms reared on agri-food waste are highlighted, including their potential as a sustainable protein source for human consumption and as feed ingredients in the livestock and aquaculture sectors.

The Influence of Different Sustainable Substrates on the Nutritional Value of Tenebrio molitor Larvae

Every year, over 30% of food production is wasted. However, promoting a sustainable food supply not only fosters economic stability in agriculture and the food industry, but also safeguards precious natural resources and ensures universal food access and safety. Therefore, the aim of the study was to determine how specific growth conditions (utilizing by-products: sprouted potatoes (1), wheat bran (2), brewers' spent grain (3), and a control sample with agar-agar gels (4)) affect the larvae of yellow mealworms (Tenebrio molitor). This includes their nutritional and energy value, consumer sensory profiling, and technological parameters of processing. The results have indicated that larvae reared on the substrate with wheat bran had the highest energy value, at 708.26 kcal. In larvae, the difference in protein content was not significant when changing the rearing conditions, and ranged between 48.54 and 59.18%. The larvae contained a significant content of fibers, with the highest amount detected in samples with brewers' spent grain. The data indicate that glucose and arabinose were distinctive to larvae. Our study has also revealed a statistical difference in ash content between larvae and the substrate, with higher levels of nitrogen, copper, and zinc detected in the larvae compared to the substrate. We have found that the salt was naturally occurring in the substrates, with the brewers' spent grain sample having the highest amount, at 1.83%. However, the control sample yielded the highest ratings, achieving a score of 7.30 for general smell acceptability. These findings emphasize the potential of utilizing various industrial and farm by-products as substrates for mealworms, transforming them into a sustainable and nutrient-rich food source. This contribution adds to the broader discourse on nutritional value and resource efficiency.

The Genome of the Yellow Mealworm, Tenebrio molitor: It's Bigger Than You Think

BACKGROUND

Insects are a sustainable source of protein for human food and animal feed. We present a genome assembly, CRISPR gene editing, and life stage-specific transcriptomes for the yellow mealworm, Tenebrio molitor, one of the most intensively farmed insects worldwide.

METHODS

Long and short reads and long-range data were obtained from a T. molitor male pupa. Sequencing transcripts from 12 T. molitor life stages resulted in 279 million reads for gene prediction and genetic engineering. A unique plasmid delivery system containing guide RNAs targeting the eye color gene vermilion flanking the muscle actin gene promoter and EGFP marker was used in CRISPR/Cas9 transformation.

RESULTS

The assembly is approximately 53% of the genome size of 756.8 ± 9.6 Mb, measured using flow cytometry. Assembly was complicated by a satellitome of at least 11 highly conserved satDNAs occupying 28% of the genome. The injection of the plasmid into embryos resulted in knock-out of Tm vermilion and knock-in of EGFP.

CONCLUSIONS

The genome of T. molitor is longer than current assemblies (including ours) due to a substantial amount (26.5%) of only one highly abundant satellite DNA sequence. Genetic sequences and transformation tools for an insect important to the food and feed industries will promote the sustainable utilization of mealworms and other farmed insects.

Waste to value: Global perspective on the impact of entomocomposting on environmental health, greenhouse gas mitigation and soil bioremediation

The innovative use of insects to recycle low-value organic waste into value-added products such as food, feed and other products with a low ecological footprint has attracted rapid attention globally. The insect frass (a combination unconsumed substrate, faeces, and exuviae) contains substantial amounts of nutrients and beneficial microbes that could utilised as fertilizer. We analyse research trends and report on the production, nutrient quality, maturity and hygiene status of insect-composted organic fertilizer (ICOF) generated from different organic wastes, and their influence on soil fertility, pest and pathogen suppression, and crop productivity. Lastly, we discuss the impact of entomocomposting on greenhouse gas mitigation and provide critical analysis on the regulatory aspects of entomocomposting, and utilization and commercialisation ICOF products. This information should be critical to inform research and policy decisions aimed at developing and promoting appropriate standards and guidelines for quality production, sustainable utilization, and successful integration of entomocompost into existing fertilizer supply chains and cropping systems.

Innovative Applications of Tenebrio molitor Larvae in Food Product Development: A Comprehensive Review

The utilization of alternative and sustainable food sources has garnered significant interest as a means to address the challenges of food security and environmental sustainability. Tenebrio molitor larvae, commonly known as mealworms, have emerged as a promising candidate in this context, as they are a rich source of nutrients and can be reared with relatively low resource input. This review article presents an in-depth analysis of the diverse range of food products developed using T. molitor larvae and the distinctive properties they bestow on these products. The review encompasses an exploration of the nutritional composition of the larvae, emphasizing their rich protein content, balanced amino acid profile, fatty acids with health benefits, vitamins, and minerals. It delves into how these attributes have been harnessed to enhance the nutritional value of a variety of food items, ranging from protein-rich snacks and energy bars to pasta, bakery goods, etc. Each of these applications is discussed with regard to how T. molitor larvae contribute to the nutritional content and sensory characteristics of the final product. Furthermore, this review sheds light on the innovative techniques and processing methods employed to incorporate T. molitor larvae into different food matrices. It addresses challenges related to taste, texture, and appearance that have been encountered and the strategies devised to overcome related problems. Overall, this comprehensive review elucidates the diverse food products that have been developed utilizing T. molitor larvae as a key ingredient. Highlighting the nutritional, sensory, and sustainability aspects of these products, this review offers valuable insights to harness the potential of this alternative protein source to meet the evolving needs of modern food systems.

Tenebrio molitor as a model system to study Staphylococcus spp virulence and horizontal gene transfer

Invertebrates can provide a valuable alternative to traditional vertebrate animal models for studying bacterial and fungal infections. This study aimed to establish the larvae of the coleoptera Tenebrio molitor (mealworm) as an in vivo model for evaluating virulence and horizontal gene transfer between Staphylococcus spp. After identifying the best conditions for rearing T. molitor, larvae were infected with different Staphylococcus species, resulting in dose-dependent killing curves. All species tested killed the insects at higher doses, with S. nepalensis and S. aureus being the most and least virulent, respectively. However, only S. nepalensis was able to kill more than 50% of larvae 72 h post-infection at a low amount of 105 CFU. Staphylococcus infection also stimulated an increase in the concentration of hemocytes present in the hemolymph, which was proportional to the virulence. To investigate T. molitor's suitability as an in vivo model for plasmid transfer studies, we used S. aureus strains as donor and recipient of a plasmid containing the gentamicin resistance gene aac(6')-aph(2″). By inoculating larvae with non-lethal doses of each, we observed conjugation, and obtained transconjugant colonies with a frequency of 1.6 × 10-5 per donor cell. This study demonstrates the potential of T. molitor larvae as a reliable and cost-effective model for analyzing the virulence of Staphylococcus and, for the first time, an optimal environment for the plasmid transfer between S. aureus carrying antimicrobial resistance genes.

Behaviour of Staphylococcus aureus in the Rearing Substrate of Tenebrio molitor Larvae

Tenebrio molitor (mealworm) is one of the most promising insect species to produce sustainable feed and food with high nutritional value. Insects may harbour microorganisms both in the gut and on the exoskeleton originating from the rearing environment. Staphylococcus aureus is a pathogenic microorganism frequently involved in food poisoning due to its enterotoxin production. This study aimed to evaluate the S. aureus growth and enterotoxins production following an experimental inoculation into the T. molitor rearing substrate (about 7 log CFU/g). Analyses on the substrate and larvae were performed over a testing period of seven days. The microbial population dynamics were also evaluated through total viable count and lactic acid bacteria count. The effects of fasting, washing, and cooking on the microbial loads of mealworms were evaluated. The results highlighted that mealworms and substrates can maintain their microbial loads of S. aureus over the tested period. Moreover, fasting and washing were generally not able to significantly reduce (p-value > 0.05) S. aureus count in mealworms. On the other hand, cooking significantly reduced (p-value < 0.001) the microbial load in almost all cases. No production of enterotoxins was revealed during the trial. Therefore, microbiological risks can be reduced by a wise choice of substrate, appropriate control measures, and thermal treatment of larvae.

Review: Recent advances in insect-based feeds: from animal farming to the acceptance of consumers and stakeholders

The search for new, alternative and sustainable feeding sources, including insects, has become an important challenge on the feed market. In 2017, the European Union (EU) started to allow the use of insect meals as feeds for fish. In addition, in 2021, the EU also authorised the use of insect meal for pig and poultry farming. However, the adoption of insect meal by the European aquaculture sector is still limited, and this is mostly due to the lack of availability of insects and their higher costs than conventional feed ingredients. Thus, the insect-based feed industry is still in its infancy, and its successful development and integration in the food value chain depend on several factors. Among these, the technical feasibility and production of quality products, and acceptance by European consumers and farmers are relevant factors. To address these points, this narrative review describes the state of the art of the potential role of insect-based feeds. The stakeholders' and consumers' perspectives are investigated, along with the effects of insect-based feeds on the production and nutritional values of fish, poultry (meat and eggs), and pork. Indeed, matching the nutritional values of insect products with conventional feeds is one of the future challenges of the insect sector, as their nutritional composition is highly dependent on the rearing substrates, and thus, their use in animal feeding needs to be investigated carefully. Feeding animals with insect-based diets affects their growth performances and the chemical composition of the derived products (fish fillets, meat, and eggs). Whether these effects can be considered positive or negative seems to depend to a great extent on the percentage of insects included in their diets and the chemical composition of the ingredients. The use of insect-based feeds has also shown a potential to improve the nutritional features and values of animal products and even to add new ones. Finally, many of the acceptance studies on the use of insects in feeds have focused mostly on the consumers' perception rather than on industry stakeholders (e.g., farmers). Future research should focus more on the farmers' perceptions on and market analyses of these innovative feeds. Even though it is likely that the upscaling of the insect sector will lead to a decrease in prices and an increase in market availability, it is still critical to understand the potential barriers and drivers for the implementation of insects as feeds from a production point of view.

Contamination of Zophobas morio Larvae Rearing Substrate with Listeria monocytogenes: A Preliminary Study

The interest in edible insects is continuously increasing due to their environmental, nutritional, and productive features. The aim of this study was to evaluate the effects and survival of Listeria monocytogenes in Zophobas morio rearing, using two different bacterial loads (2 and 6 log CFU/g). We also considered the effect of washing, fasting, and cooking treatments on the larvae. During the experimental trial, no mortality was observed among the larvae. The L. monocytogenes loads decreased over time, and it was below the detection limit for crates inoculated with 2 log CFU/g, while the substrate inoculated with 6 log CFU/g reached loads of 4.26 (without larvae) and 2.83 log CFU/g (with larvae). Due to the absence of L. monocytogenes in the larvae on day seven, it was not possible to assess the fasting treatment or the washing and the cooking. However, when looking at the total microbial count, significant effects were revealed for all treatments. The unfasted larvae showed no effect of washing, while the total microbial counts decreased after washing in the fasted larvae. This proves that fasting is a good treatment in terms of hygiene assurance for the consumer.

Dietary utilization of mealworm frass in rabbit feeding regimes and its effect on growth, carcass characteristics, and meat quality

This study aimed to shed light on the use of mealworm (Tenebrio molitor) frass (TMF) in rabbit diets and its effects on growth performance, blood profiles, rabbit meat quality, and fatty acid profiles. A total of 48 Gabali rabbits were divided equally and randomly into four groups to be fed one of four dietary treatments: a control (T0) group and three TMF groups, which included TMF meal at 1 (T1), 2 (T2), and 3 (T3) %, respectively. The rabbits were fed on isonitrogenous and isoenergetic diets for 11 weeks, and the growth performance data were recorded. Six rabbits per group were slaughtered at the end of the 11th week, then the pharmacochemical parameters and carcass traits were measured, and meat quality and fatty acid profiles were analyzed. The results indicated that the growth performance of different groups was similar (P > 0.05). The levels of globulin, glucose, and alanine transaminase (ALT) were lower in the mealworm frass groups compared with the control group. Carcass traits were not affected by experimental regimes. Fat was higher in the TMF treatment groups, while moisture was lower compared with the control group. The shear force had a lower value in the treatment groups T3 and T2 compared with the control group. The highest values of redness and chroma (color parameter) of rabbit meat were observed in the treatment groups vs. the control group. Moreover, the proportion of total saturated fatty acids in the meat of rabbits that were fed on the T2 and T3 diets was higher compared to those fed on the control (i.e., T0) and T1 diets. Furthermore, the proportion of monounsaturated fatty acid was higher in the T2, T3, and T1 groups vs. T0 rabbits, whereas the PUFA proportions were lower. It could be concluded that frass has great potential to be used as a partial substitute for rabbit diets.

Edible Insects’ Transformation for Feed and Food Uses: An Overview of Current Insights and Future Developments in the Field

The integration of insect-derived extracts in feed and food products has become a field of growing interest in recent years. In this review, we collect different studies carried out on edible insects’ transformation processes and focus on the various treatment operations, extraction technologies, and solvents used in different processing steps. We include an overview of current insights into the different steps of the transformation process: insect reception, killing methods, pretreatments, storage, delipidation, protein extraction, as well as chitin and chitosan extraction. Finally, we reflect on the most important future challenges of this sector.

Exploring the Future of Edible Insects in Europe

The effects of population increase and food production on the environment have prompted various international organizations to focus on the future potential for more environmentally friendly and alternative protein products. One of those alternatives might be edible insects. Entomophagy, the practice of eating insects by humans, is common in some places but has traditionally been shunned in others, such as European countries. The last decade has seen a growing interest from the public and private sectors to the research in the sphere of edible insects, as well as significant steps forward from the legislative perspective. In the EU, edible insects are considered novel foods, therefore a specific request and procedure must be followed to place them in the market; in fact, until now, four requests regarding insects as a novel food have been approved. Insects could also be used as feed for livestock, helping to increase food production without burdening the environment (indirect entomophagy). Market perspectives for the middle of this decade indicate that most of the demand will be from the feed sector (as pet food or livestock feed production). Undoubtedly, this sector is gaining momentum and its potential relies not only in food, but also in feed in the context of a circular economy.

Insect as feed ingredients for pigs

Among edible insects, black soldier fly (Hermetia illucens), yellow mealworm (Tenebrio molitor), and common housefly (Musca domestica) have been considered as an alternative protein source for pigs. Because they are easy to breed and grow in the organic wastes, and they have well-balanced nutritional value as a protein source for pigs. The black soldier fly larvae and mealworm could replace the fish meal in the diets for weaned pigs without adverse effects on growth performance and nutrient digestibility. Black soldier fly could also be included in the finishing pig's diet without any negative effects on the growth performance and pork quality of the market pigs. Insect products showed a greater standardized ileal digestibility value of amino acids than conventional animal proteins in growing pigs. Due to the limited amount of insect products used for pig feeding study, most previous pig studies have been conducted in weaned pigs. Thus, further study is needed about the optimal inclusion level of insect products in every phase diet from weaned pigs to sows. The use of insect products in swine diets has some challenges in terms of cost, supply, and safety. Lastly, intrinsic differences among insect species, processing method, and feeding phase should be taken into consideration for the use of insect products in the swine diets.