Black soldier fly (Hermetia illucens) larvae as potential feedstock for the biodiesel production: Recent advances and challenges

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

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

Feed-shifting strategy for increasing biodiesel production from black soldier fly larvae

The aim of this study was to increase the bioconversion efficiency (lipid accumulation) of black soldier fly larvae while simultaneously increasing biodiesel production through a feed-shifting strategy. Feeding with low-lipid feed promoted an increase in larval weight, while high-lipid feed resulted in greater lipid accumulation. Based on this result, a feed-shifting strategy was introduced, which consisted of two stages: first, increasing larval body weight using low-lipid feed, followed by lipid induction for biodiesel production using high-lipid feed. The use of this strategy resulted in an increase in the dry weight of larvae by ≥16 % compared to single feeding systems. This led to a 20 % increase in biodiesel productivity. The waste reduction ratio was enhanced due to the higher bioconversion rate in the feed-shifting strategy compared to that in the single feeding systems. The feed-shifting strategy would contribute to the enhancement of waste-to-energy efficiency.

Rearing of Black Soldier Fly Larvae with Corn Straw and the Assistance of Gut Microorganisms in Digesting Corn Straw

Corn straw is considered a renewable biomass energy source, and its unreasonable disposal leads to resource waste and environmental pollution. Black soldier fly (Hermetia illucens L.) larvae (BSFL) facilitate the bioconversion of various types of organic wastes. In this study, we found that 88% of BSFL survived, and 37.4% of corn straw was digested after 14 days of feeding with corn straw. Contrary to expectations, the pretreatment of corn straw with alkaline hydrogen peroxide did not promote its digestion but rather reduced the growth and survival rates of BSFL. Acinetobacter, Dysgonomonas, and unclassified Enterobacteriaceae were the abundant genera in the BSFL gut fed with corn straw. Compared with the standard diet, the relative abundances of carbohydrate metabolism genes, such as the gene abundances of β-glucosidase and α-glucosidase, were higher with corn straw as the substrate. These results suggested that the gut microbial community could regulate suitable and functional microorganisms in response to the substrates. Furthermore, four cellulase-producing strains, namely Klebsiella pneumoniae, Proteus mirabilis, Klebsiella oxytoca, and Providencia rettgeri, were isolated from the guts of corn straw BSFL. These four strains helped increase the conversion rates of corn straw, the weights of BSFL, and survival rates. In summary, we reared BSFL with corn straw and discovered the functions of gut microorganisms in adapting to the substrates. We also isolated four cellulase-producing strains from the BSFL guts and declared the benefits of BSFL digesting corn straw.

Microplastics in the diet of Hermetia illucens: Implications for development and midgut bacterial and fungal microbiota

In a world with a population exceeding 8 billion people and continuing to grow, pollution from food and plastic waste is causing long-term issues in ecosystems. Potential solutions may be found by exploiting insect-based bioconversion. In this context, we investigated the impact of polyvinyl chloride microparticles (PVC-MPs) on the development of Hermetia illucens (black soldier fly; BSF) and its midgut bacterial and fungal microbiota. The impact of PVC-MPs was evaluated feeding BSF larvae with a PVC-MPs-supplemented diet. The larvae exposed to different PVC-MPs concentrations (2.5%, 5%, 10% and 20% w/w) developed into adults with no significant increase in pupal mortality. Faster development and smaller pupae were observed when 20% PVC-MPs was provided. The BSF larvae ingest PVC-MPs, resulting in a reduction in MPs size. Larvae exposed to PVC-MPs did not exhibit differences in gut morphology. Regarding the impact of PVC-MPs on the structure of both bacterial and fungal communities, the overall alpha- and beta-diversity did not exhibit significant changes. However, the presence of PVC-MPs significantly affected the relative abundances of Enterobacteriaceae and Paenibacillaceae among the bacteria and of Dipodascaceae and Plectospharellaceae among the fungi (including yeast and filamentous life forms), suggesting that PVC-MP contamination has a taxa-dependent impact. These results indicate that BSF larvae can tolerate PVC-MPs in their diet, supporting the potential use of these insects in organic waste management, even in the presence of high levels of PVC-MP contamination.

Sexual dimorphism in the structural colours of the wings of the black soldier fly (BSF) Hermetia illucens (Diptera: Stratiomyidae)

The black soldier fly (BSF) Hermetia illucens (Diptera: Stratiomyidae) plays a significant role at the larval stage in the circular economy due to its ability to convert organic waste into valuable products for energy, food, feed, and agricultural applications. Many data are available on larval development and biomass generation, but basic research on this species is lacking and little is known about adult biology, in particular about the cues involved in sexual recognition. In the present study, using various instruments (stereomicroscope, scanning and transmission electron microscope, hyperspectral camera and spectrophotometer), wing ultrastructure of both sexes was analysed, reflectance and transmission spectra of the wings were measured and behavioural bioassays were carried out to measure male response to specific visual stimuli. The collected data showed the existence of sexual dimorphism in the wings of H. illucens due to iridescent structural colouration generated by a multilayer of melanin located in the dorsal lamina of the central part of the wing. Wing sexual dimorphism is particularly evident regarding the strong emission of blue light of female wings. Blue colour induces in males a strong motivation to mate. The obtained results can help to improve and optimize the breeding techniques of BSF.

A cell line derived from the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae)

Insect cell lines are effective tools used in industry and academia. For example, they are used in screening potential insecticides, in making certain proteins for biomedical applications, and in basic research into insect biology. So far, there are no cell lines derived from the black soldier fly, Hermetia illucens (BSF). This may become an issue because BSFs are employed in a range of industrial and household processes. BSFs are used in producing biodiesel, in developing cosmetics and skin creams, and in the production of some medicines and animal feeds. BSF larvae process waste streams from a variety of sources into food for some animals and are also used in household composting. Our BSF cell line, designated BCIRL-HiE0122021-SGS, was developed from eggs using the medium CLG#2 (50% L-15 + 50% EX-CELL 420, with 9% FBS and antibiotics), with many other media being tested. This cell line consists of attached cells with a variety of morphologies and its identity was authenticated using CO1 barcoding. A growth curve was generated and the resulting doubling time was 118 h. We quantified the fatty acid methyl esters (FAMES) and recorded the expected range of saturated, monounsaturated, and polyunsaturated FAMEs, with only trace levels of lauric acid being noted. The BSF cell line is available free of charge by request.

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

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

Effect of moisture content on larval gut microbiome and the conversion of pig manure by black soldier fly

The study investigated the influence of varied moisture levels in pig manure on the gut microbiome of black soldier fly larvae (BSFL) and their waste conversion efficiency. This encompassed alterations in nutrient components of both BSFL and pig manure, diversity and characterization of the BSFL gut microbiota, and the reciprocal effects between the BSFL gut microbiota and their growth performance and nutrient composition. Additionally, the investigation delved into the changes in the bacterial community and the presence of potential pathogenic bacteria in pig manure. An initial mixture of fresh pig manure and wheat bran was prepared with a 60 % moisture content (Group A). Distilled water was subsequently added to adjust the moisture levels, resulting in mixtures with 65 % (Group B), 70 % (Group C), and 75 % (Group D) moisture content. Each group underwent BSFL digestion over ten days. Groups C (3.87 ± 0.05 mg/worm) and D (3.97 ± 0.08 mg/worm) showed significantly higher bioconversion efficiencies and enhanced BSFL growth compared to Groups A (2.66 ± 0.21 mg/worm) and B (3.09 ± 0.09 mg/worm) (P < 0.05). A 75 % moisture level was identified as ideal, positively influencing fecal conversion efficiency (FCE) (9.57 ± 0.14 %), crude fat intake (8.92 ± 0.56 %), protein (46.60 ± 0.54 %), and total phosphorus (1.37 ± 0.08 %) from pig manure, and subsequent nutrient accumulation in BSFLs. A decline in larval crude ash content indicated higher organic matter and an increased pig manure conversion rate with elevated moisture. High-throughput sequencing and diversity analyses confirmed different moisture contents influenced the BSFL gut microbiota. Bacteroidetes (32.7-62.0 %), Proteobacteria (6.8-29.3 %), Firmicutes (5.8-23.4 %), and Actinobacteria (1.9-29.0 %) were predominant phyla. A 75 % moisture content significantly impacted the BSFL biomass conversion and growth performance. Additionally, Larval feces met non-hazardous fertilizer standards, according to NY-525 (2012).

Evaluation of Growth Performance and Environmental Impact of Hermetia illucens Larvae Reared on Coffee Silverskins Enriched with Schizochytrium limacinum or Isochrysis galbana Microalgae

Hermetia illucens is a promising insect due to its ability to convert low-value substrates as food chain by-products into highly nutritious feed. Its feeding and nutrition are important issues. The aim of this work was to investigate the effect of different substrates consisting of coffee silverskin, a by-product of the roasting process, enriched with different inclusions of microalgae (5%, 10%, 20%, and 25%), Schizochytrium limacinum, and Isochrysis galbana, combined with the assessment of environmental sustainability by LCA. In general, the addition of microalgae led to an increase in larval growth performance due to the higher content of protein and lipids, although S. limacinum showed the best results with respect to larvae fed with coffee silverskin enriched with I. galbana. A higher prepupal weight was observed in larvae fed with 10%, 20%, and 25% S. limacinum; shorter development times in larvae fed with 25% of both S. limacinum and I. galbana; and a higher growth rate in larvae fed with 25% S. limacinum. The 10% S. limacinum inclusion was only slightly different from the higher inclusions. Furthermore, 10% of S. limacinum achieved the best waste reduction index. The greater the inclusion of microalgae, the greater the environmental impact of larval production. Therefore, the addition of 10% S. limacinum appears to be the best compromise for larval rearing, especially considering that a higher inclusion of microalgae did not yield additional benefits in terms of the nutritional value of H. illucens prepupae.

Laboratory-adapted and wild-type black soldier flies express differential plasticity in bioconversion and nutrition when reared on urban food waste streams

BACKGROUND

The black soldier fly (BSF) offers a potential solution to address shortages of feed and food sources; however, selecting effective rearing substrates remains a major hurdle in BSF farming. In an urban area like Singapore, current practice is based on rearing BSF on homogeneous waste streams (e.g., spent brewery grains or okara) because heterogeneous food wastes (e.g., mixed kitchen/canteen waste or surplus cooked food) present several operational challenges with respect to the standardization of development, nutritional content, and harvesting.

RESULTS

In this study, we compared two genetic strains of BSF larvae (wild-type and laboratory-adapted line) in a bioconversion experiment with diverse types of food waste (homogeneous/heterogeneous; plant/meat) and we quantified the phenotypic plasticity. Our results demonstrate different plasticity in bioconversion performance, larval growth and larval nutrition between the two BSF lines. This difference may be attributed to the selective breeding the laboratory-adapted line has experienced. Notably, larval lipid content displayed little to no genetic variation for plasticity compared with larval protein and carbohydrate content. Despite variation in larval development, heterogeneous food wastes can produce better performance in bioconversion, larval growth, and larval nutrient content than homogeneous food waste. All-meat diets result in high larvae mortality but larval survival could be rescued by mixing meat with plant-based food wastes.

CONCLUSION

Overall, we suggest using mixed meals for BSF larvae feeding. Targeted breeding may be a promising strategy for the BSF industry but it is important to consider the selection effects on plasticity in larval nutrition carefully. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Controlled crushing device-intensified direct biodiesel production of Black Soldier Fly larvae

Insect larvae contain sufficient oil comparable with oleaginous biomass, and hence have potency as alternative biodiesel resources. The direct transesterification of Black Soldier Fly (BSF) larvae have conducted using a controllable crushing device (CCD) and a homogeneous base as a catalyst. The effect of catalyst concentration (wt.%), ratio BSF larvae to methanol (wt./v), reaction time (min) and rotational speed (rpm) on biodiesel conversion was determined. The maximum conversion of 93.8% was achieved at room temperature after 20 min of reaction time and ratio larvae to methanol of 1:2 (wt./v), catalyst concentration of 7 wt% and rotational speed of 3000 rpm. In addition, the green metrics calculation showed that this method produces less waste and uses less solvent. Some of the BSF-biodiesel properties meet the biodiesel standard. The CCD-intensified the DT of BSF larvae is a promising alternative for green and energy-saved biodiesel production.

Effects of Black Soldier Fly Larvae (Hermetia illucens Larvae) Meal on the Production Performance and Cecal Microbiota of Hens

The effects of Hermetia illucens larvae meal (HILM) as a feed supplement on production performance and cecal microflora were studied in 900 Hy-line Brown laying hens. Laying hens (60 weeks old) were randomly divided into four groups. Each group had five replicates, and each replicate had 45 hens. The control group was fed with a corn-soybean-based diet, and the experimental groups were fed with 1% HILM, 2% HILM, or 3% HILM. Results were as follows: (1) With the increase in HILM level, the laying rate increased linearly (p ≤ 0.05), and the feed/egg and cracked-egg rate decreased linearly (p ≤ 0.05). (2) Community composition analysis showed that the dominant bacteria in each group were Bacteroidetes and Firmicutes, followed by Actinobacteria and Proteobacteria, which accounted for more than 97% of 16S rRNA gene sequence of the total cecal bacteria. (3) Alpha diversity analysis at the operational taxonomic unit classification level showed that the HILM-addition groups had higher community richness and community diversity than the control group. (4) Principal co-ordinates analysis showed that the cecum samples in each group were significantly separated (p ≤ 0.05). At the phylum level, the relative abundance of Bacteroidetes in the HILM addition groups was significantly lower than that in the control group (p < 0.001), and the relative abundance of Firmicutes in the HILM addition groups was significantly higher than that in the control group (p < 0.001). In conclusion, dietary HILM supplementation had a significant effect on the production performance and cecal microflora of laying hens at the late laying period under the conditions of this experiment but had no adverse effect on the intestinal dominant flora.

Co-Immobilization of Lipases with Different Specificities for Efficient and Recyclable Biodiesel Production from Waste Oils: Optimization Using Response Surface Methodology

Lipase-catalyzed transesterification is a promising and sustainable approach to producing biodiesel. To achieve highly efficient conversion of heterogeneous oils, combining the specificities and advantages of different lipases is an attractive strategy. To this end, highly active Thermomyces lanuginosus lipase (1,3-specific) and stable Burkholderia cepacia lipase (non-specific) were covalently co-immobilized on 3-glycidyloxypropyltrimethoxysilane (3-GPTMS) modified Fe₃O₄ magnetic nanoparticles (co-BCL-TLL@Fe₃O₄). The co-immobilization process was optimized using response surface methodology (RSM). The obtained co-BCL-TLL@Fe₃O₄ exhibited a significant improvement in activity and reaction rate compared with mono and combined-use lipases, achieving 92.9% yield after 6 h under optimal conditions, while individually immobilized TLL, immobilized BCL and their combinations exhibited yields of 63.3%, 74.2% and 70.6%, respectively. Notably, co-BCL-TLL@Fe₃O₄ achieved 90-98% biodiesel yields after 12 h using six different feedstocks, demonstrating the perfect synergistic effect of BCL and TLL remarkably motivated in co-immobilization. Furthermore, co-BCL-TLL@Fe₃O₄ could maintain 77% of initial activity after nine cycles by removing methanol and glycerol from catalyst surface, accomplished by washing with t-butanol. The high catalytic efficiency, wide substrate adaptability and favorable reusability of co-BCL-TLL@Fe₃O₄ suggest that it will be an economical and effective biocatalyst for further applications.