Bioconversion Of Organic Waste Research Articles

Bioconversion of organic wastes: treatment sludges, animal manures, and agricultural wastes

AbstractThis study aimed to investigate the compostability of treatment sludge and to determine the effects of adding different animal manures (cattle, pig, horse, and chicken) and agricultural waste (sunflower stalks) on the composting process. Five different compost reactors (M1, M2, M3, M4, and M5) were operated. Sunflower stalks were added to all reactors as a bulking agent at the rate of 20%. Treatment sludge (80%) and bulking agent were added to the M1 reactor, where animal manure was not added, while 40% treatment sludge and 40% animal manure were added to the other reactors. In the reactors where animal manure was added, cattle (M2), pig (M3), horse (M4), and chicken (M5) manure were used, respectively. The temperature, pH, electrical conductivity, organic matter (OM), carbon to nitrogen ratio (C/N), total Kjeldahl nitrogen, and total phosphorus were monitored during the 21-day process. The highest OM loss (64.8%) occurred in the M2 reactor, and the maximum temperature (62.7 °C) was achieved. The high temperatures reached in the reactor increased microbial activity, resulting in rapid decomposition of OM and elimination of pathogens. With a maximum reduction in the C/N ratio (40%), carbon and nitrogen balance was achieved, thus obtaining a more stable and higher quality compost for plants in this reactor. In the M1 reactor, where only treatment sludge was composted, lower microbiological activity occurred compared to the other mixtures due to the lack of substrate. It can be said that composting treatment sludge together with animal manures will provide higher quality end products.

ECR Spotlight – Pedro Duarte

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Pedro Duarte is an author on ‘Tracking lipid synthesis using 2H2O and 2H-NMR spectroscopy in black soldier fly (Hermetia illucens) larvae fed with macroalgae’, published in JEB. Pedro is a PhD student in the lab of Ivan Viegas at the University of Coimbra, Portugal, investigating edible insect metabolism and nutritional value, and their role in the bioconversion of organic waste and improving food security.

Pathogen inactivation from faecal waste via black soldier fly treatment

Sustainable development goal 6.2 advocates for increasing access to equitable and adequate hygiene and sanitation for all by 2030, and its indicator target is to raise the proportion of the population using safely managed sanitation. On the contrary, it is approximated that only 54% of people globally have access to safely managed sanitation, while 2.4 billion lack access. Recent innovations have however seen the development of low-cost technologies that can be customized depending on the region. The container based sanitation (CBS) is one of the options for safely managing the waste compared to conventional sewerage systems that are expensive. However, the need for emptying and transportation of filled fecal sludge (FS) containers on daily basis, leads to high operational costs and increases the operational exposures risks to fecal pathogens amongst the CBS operators. The study determined the performance efficiency of Black Soldier Fly Larvae in inactivation of E.coli via seeded container based sanitation- Urine diverting dry toilet model. Sample was transported to the lab for analysis of E.coli after every 3 days from Seeded households and samples from Non seeded households in replication. One gram of sample was used in serial dilution up to factor 5.The inoculum was plated in Tryptone Bile Glucuronic (TBX) agar for enumeration according to manufacturer’s instructions. Plates with 30-300 colonies were considered viable for counting. The study used statistical analysis IBM SPSS software from the sets of experiments. The E.coli (CFU/ml) mean varied between 7.3±1.3 and 10.1±2.8 for Seeded treatments while non-seed treatments ranged between 7.5±1.6 and 10.4±3.2. A significant variation occurred between the two treatments at p<0.05(SH and NH). Findings from this study showed that there was reduction of E.coli coliforms with Bioconversion of organic waste using the BSF technology has been noted to reduce the E.coli load and reducing the volume of the bio-waste. Sanitation policy makers can apply the findings of this study in formulation of policies on safe handling and disposal of fecal matter from onsite sanitation facilities.

Analysis of Maggot Nutrition in Various Farming Periods and Organic Wastes as a Growth Medium

Undoubtedly, the bioconversion of organic waste into maggots is an innovation to reduce organic waste generation. Nonetheless, maggot cultivators only use available organic waste as feed, without adjustments, which makes the nutritional value of maggot produced inconsistent. The current study aims to determine appropriate organic waste and farming periods based on the nutritional value of maggots. This research was conducted using a field-scale experimental method for 21 days. A total of 9 experimental variations of organic waste type and farming period were observed, i.e., kitchen waste, rotten vegetables, and a mixture of both (50:50, w/w) for 7, 14, and 21 days of farming, respectively. The results showed that the appropriate organic waste for maggot farming is kitchen waste, with a farming period of 14 days. During the 14-day farming process, maggot weight increased 1,750 times to 3,500 grams, with protein and fat content of 38.28% and 28.47%, respectively. The protein content in maggot meets the minimum requirements for fish and poultry use as an alternative feed.

Genetic structure of black soldier flies in northern Iran.

The black soldier fly (BSF), Hermetia illucens, is known for nutrient-recycling through the bioconversion of organic waste into protein-rich insect larvae that can be processed into an animal feed ingredient. However, information on species distribution and its genetic structure in Iran is scarce. We directed a survey on the Caspian Sea coast, with a reconstructing demographic relationships study using two parts of mitochondrial cytochrome C oxidase 1 (COI) gene (barcode and 3' end regions) and nuclear internal transcribed spacer 2 (ITS2) to identify BSF' genetic diversity in retrospect to the global diversity and the potential origin of the Iranian BSF population. Larvae and adults were recovered from highly decomposed poultry manure, in May 2020. Sequence analysis of both regions of COI gene (about 1500 bp) revealed a single haplotype, identical to that of haplotype C, a worldwide commercial strain originated from Nearctic, Palearctic, or African biogeographic regions. However, the ITS2 locus was confirmed to be invariable across samples from diverse biogeographic regions. The results proved the presence of BSF in north of Iran. However, it is not possible to determine with certainty when and where this species first established in Iran, and they have likely been released to nature due to the existence of companies importing and breeding such flies. Due to heavy international trading, the introduction and settlement of this fly in the southern coasts of the country is highly suggested.

Bioconversion of Organic Wastes by Black Soldier Fly for Chitin, Lipid and Protein Production

The bioconversion of organic waste into black soldier fly (BSF) larvae, which is a valuable source of lipid, and protein, is part on an ongoing creative effort in valorising waste. Besides lipid and protein, BSF larvae also contain significant amounts of chitin, a polymer of N-acetylglucosamine that make up the backbone of the polysaccharide structure normally found in insects. In this study, the effects of organic waste type and moisture content on biomass conversion ratio were investigated. BSF larval development (larvae to prepupae to pupae) was found to occur to the highest extent (98.90 ± 0.71 % biomass converted) when kitchen waste (KW) was used compared to when vegetables waste (VW) (84.6 ± 1.41 % biomass converted) or fruit waste (FW) was used (87.5± 0.71 % biomass converted). The optimal moisture content of the kitchen waste was found to be 80 %, which results in the highest waste biomass conversion of 99.8 % ± 0.58. The BSF larvae were found to have approximately 38 – 42 % crude lipid, 34 – 41 % crude protein, and 8 – 9 % ash content. Chitin was isolated through a three-step process of deproteinization, demineralization, and decolorization. A yellowish-grey powder was obtained at the end of the isolation process and the chitin yield was determined to be 4 – 6% (g/g). Fourier transform infra-red (FTIR) analyses confirmed the chitin yield by identifying the -OH, -CH3CONH, and -CO stretching of its polysaccharides and glucosamine rings; and the lipid yield by noting the disappearance of the hydroxyl stretching that had been present in the spectra of unprocessed BSF larvae, and the appearance of X–H stretching which indicates the presence of triglyceride functional groups.

Studies on Vermicomposting of Sericultural Wastes: An Eco-Friendly Approach for Effective Management of Seri-Wastes

Vermicompost is one of the most essential and efficient organic manure commonly applied to the mulberry field in most the advance sericulture countries. Vermicompost is the one of the beneficial biotechnology is the bioconversion of organic waste into useful form. In the current experiment, soil treated with vermicompost of three different treatments viz., Cow dung + Seri-waste (T-1), Cow dung +Seri-waste (T-2) and Cow dung +Seri-waste + Rice straw (T-3) were recorded different parameters. After the application of different treatment of vermicompost the best recorded treatment as a T-as 6.7 pH. The moisture retention capacity was recorded as 52% in T-1 and 74% and 62% respectively in T-2 and T-3, with electric conductivity as 2-3ms/cm. The soil texture of soil treated with T-2 (Cow dung +Seri-waste) showed best input as 50% as compared to T-1 and least in T-3 as 40% and 35% respectively. Application of different treatment of vermicompost on soil recorded to be T-2 (Cow dung +Seri-waste) showed positive response and high availability of microorganisms that are beneficial for the mulberry plant. The germination percentage of seed of mulberry treated with different treatment was recorded to be highest of 90% in T-2 and root and shoot length of plant grown as 26cm and 12cm as compared to T-1 and T-3 as 19 cm and 8cm, 34cm and 10cm respectively. Similarly, the moisture percentage and moisture retention capacity of T-2 was recorded to be highest as 74.64% and 73.21% respectively. Therefore, the current experiment opens new avenues vermicompost substrate for promoting of by-product utilization seri-waste in sericulture. The resultant product could be utilized for agricultural and horticultural as well. The present results offer numerous scopes for further sustainable agriculture with special emphasis on sericulture industry.

Aplikasi limbah padat budidaya maggot terhadap pertumbuhan dan produksi tanaman pakcoy (Brassica chinensis L.)

Bioconversion of organic waste can use the agent of black soldier fly larvae (Hermetia illucent) or maggot. Maggot cultivation residue can be used as plant fertilizer. This study aimed to determine the effect of the application of maggot cultivation solid waste and the optimal dose that could be used to increase the growth and productivity of pakchoi (Brassica chinensis L.). The study was conducted in a greenhouse with a completely randomized design (CRD) with 5 treatments, namely the dose of maggot solid waste (0, 90, 180, 270, and 360 grams) on planting media with a total weight of 4180 grams per polybag. Each treatment consisted of 5 replications. The results showed that the application of solid waste of maggot cultivation had a significant effect on plant height, the number of leaves, plant fresh weight, and plant dry weight but had no significant effect on root length. Application of a dose of 180 grams on plant media gave the highest average yield compared to other doses. This study concludes that the solid waste of maggot cultivation can be used as organic fertilizer to increase plant productivity.

Recycling different textile wastes for methane production: Morphological and microstructural changes and microbial community dynamics

The dramatic increase of textile wastes has become a major global concern, which calls for alternative practices to alleviate severe environmental pollution and waste of resources due to their improper disposal and management. Anaerobic digestion (AD) is a cost-effective and eco-friendly technology that allows the bioconversion of organic wastes into clean energy (methane), which might be potentially useful for recycling textile wastes. In this study, AD was applied to 11 commonly available textile wastes in daily life to explore their feasibility, along with the methane production efficiency, biodegradability (BD), degradation mechanism, and microbial community dynamics during AD. The results showed that all textile wastes presented an obvious decomposition from an integrated shape to fragmented pieces within 18 days except blue denim. The highest experimental methane production (EMP) of 356.0 mL/g volatile solids (VS) and BD of 78.0 % were obtained with flax. The degradation mechanism could be concluded that predominant bacteria, especially Clostridium sensu stricto, first attached to the surface of textile waste and converted its main compositions cellulose and hemicellulose into acetate as the core intermediate. Then, acetate was utilized by the major methanogen, Methanothrix, through the acetoclastic methanogenesis pathway to produce methane. This study not only enriches the understanding of textile wastes degradation mechanisms during AD and provides very useful data on methane production from commonly available textile wastes but also proposes a promising method for efficiently recycling and utilizing the diverse range of textile wastes to reduce waste pollution and generate clean energy simultaneously.

The Effect of Biofertilizer from Waste Bioconversion on The Growth of Cocoa Seedlings

Organic waste can be a source of environmental pollution if not managed properly. The organic waste transformed by Black Soldier Fly (BSF) larvae produces liquid biofertilizer (LB) containing nutrients and beneficial microbes for plants. This study aims to determine the effect of dosage and frequency of application of liquid biofertilizer on the growth of cocoa seedlings and soil properties. The experiment used a randomized complete block design with seven treatments and four replications. The treatments were a control, LB 3% every two weeks, LB 3% every four weeks, LB 6% every two weeks, LB 6% every four weeks, LB 12% every two weeks, LB 12% every four weeks. The results showed that LB 6% every four weeks was the best treatment in increasing seedling height, stem diameter, and weight of fresh shoot, dry shoot, and dry roots of cocoa seedlings at 20 weeks old compared to other treatment. The application of LB significantly increased soil pH, but not significantly affected on the content of organic C, total N, available P and exchangeable cations at soil. Biofertilizer from bioconversion of organic waste using BSF larvae is suitable to improve the growth of cocoa seedlings.

Effects of biochar amendment on bioconversion of soybean dregs by black soldier fly

Biochar is known to accelerate composting process and improve the quality of end-products. However, its effects on bioconversion of organic waste by black soldier fly larvae (BSFL) remains largely unexamined. To investigate the effects of corn straw biochar (CS-BC) on bioconversion of soybean dregs (SD) by BSFL, SD was amended with four different dosages of CS-BC [0%, 2%, 5%, and 8% (w/w)] and digested by BSFL for ten days. The results indicated that the peak values of single larva wet weight in the treatments amended with CS-BC were advanced by 2–3 days and the reduction rate of SD increased from 72.09% to 85.37% with the increasing dosage of CS-BC. Meanwhile, SD mixed with 2%, 5% and 8% of CS-BC decreased ammonia (NH3) emission by 2.7%, 3.6% and 18.0%, respectively. The nitrous oxide (N2O) emissions reduced (−23.6%, −29.1% and −49.2%) with 2%, 5% and 8% CS-BC additions, respectively. In addition, the residual nitrogen of SD‑nitrogen proportionally increased with CS-BC application (28.3%, 28.6%, 30.1% and 35.0% for application at the dosage of 0%, 2%, 5% and 8%, respectively). Based on the comprehensive evaluation of bioconversion performance, alleviation of pollutant gas emission, and nitrogen conservation, we recommend the introduction of 8% (w/w) CS-BC during bioconversion of SD by BSFL. This study confirmed the feasibility of CS-BC as an amendment for the BSFL-based bioconversion system.

Odorant binding proteins from Hermetia 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 in Hermetia 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 recombinant H. illucens OBPs (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.

Creating wealth from waste: An approach for converting organic waste in to value-added products using microbial consortia

In the current scenario, great emphasis is being made on the recovery, recycling, and reconditioning of organic solid waste. With a focus on the bioconversion of organic waste into value-added products, municipal vegetable waste was fractionated into liquid and solid part. The solid fraction was subjected to biodegradation in the presence of different microbial consortia and different enzymes were extracted. The remaining solid stuff was converted into animal feed, followed by the evaluation of its microbiological and chemical indices. Liquid fraction separated from waste was used as a crude medium to grow different bio-fertilizer strains. Among the three consortia, consortium C (Aspergillus terreus and Myrothecium verrucaria) showed the maximum production of amylase, cellulase, xylanase and pectinase after 4 days. Results of the microbiological and chemical parameters of the animal feed prepared from the fermented vegetable waste showed that the various parameters were found to be within the permissible limit. The average concentrations of heavy metals in the compost was found to be within the permissible limit of FCO standard, therefore, it can also be used for agricultural application. For using liquid extract of the vegetable waste, maximum CFU count 1.9 × 106, 1.1 × 106, and 8.7 × 105 was achieved in BAB 1980, BAB 662, and BAB 267 strain, respectively after 30 h of incubation. Thus, the present study demonstrated the bioconversion of vegetable waste into crude enzymes, animal feed, compost, and liquid biofertilizer.

Analysis of the use of media resulting from bioconversion of organic waste in the production of maggots BSF (black soldier fly)

Maggots is an organism derived from the eggs of the black fly, Hermentia illucens (black soldier fly, BSF), which undergoes metamorphosis in the second phase after the egg phase and before the pupa phase which then turns into an adult fly. The purpose of this study was to analyze the utilization of organic waste substrate on the production of BSF maggots cultivation. This research was conducted outdoor at the Freshwater Aquaculture Fisheries Center (BPBAT) Sungai Gelam Jambi with a completely randomized design (CRD) with 4 treatments and 3 replications; Treatment A: PKM (palm kernel meal) 100%, B (PKM 50% + cabbage vegetable waste 50%), C (PKM 50% + coconut pulp 50%) and D (PKM 50% + coconut pulp 25% + vegetable waste cabbage 25%). The average yield parameter of high maggots biomass in treatment A was 673.67 g/4 kg substrate and the lowest biomass in treatment D was 239.67 g/4 kg substrate. For the average weight and length of the best maggots in treatment A (0.20 g/individual) and (1.83 cm), the lowest was in B (0.12 g/Ind. and 1.58 cm). The highest was in treatment B (5,182.31 individual/4 kg substrate) and the lowest was in D (1,479.44 ind./4 kg substrate. The highest bioconversion value of maggots to organic matter OSE (organic substrate efficiency) was highest in treatment A (16, 84%) and the lowest was in D (5.99%). Technically, treatment A was slightly better than B, while economically the best organic substrate medium for maggots cultivation was in treatment B with a production cost of Rp. 7.257 and the ECR (economic conversion ratio) value of 5.81 was lower than the other 3 treatments.
 
 Keywords: Maggots, black soldier fly, Hermentia illucens, organic waste.
 
 ABSTRAK
 
 Maggots merupakan organisme yang berasal dari telur seranga lalat hitam, Hermentia illucens (black soldier fly, BSF). Tujuan penelitian ini yaitu menganalisis pemanfaatan subtrat limbah organik terhadap produksi budidaya maggots BSF. Penelitian ini dilaksanakan di Balai Perikanan Budidaya Air Tawar (BPBAT) Sungai Gelam, Jambi dengan rancangan acak lengkap (RAL) 4 perlakuan 3 ulangan yaitu perlakuan A : PKM (palm kernel meal) 100%, B (PKM 50% + limbah sayur kol 50%), C (PKM 50% + ampas kelapa 50%), dan D (PKM 50% + ampas kelapa 25%+ limbah sayur kol 25%).Rata-rata biomassa tertinggi didapatkan pada perlakuanA (673,67g/4 kg subtrat) dan biomassa terendah dihasilkan pada perlakuan D (239.67g/4 kg subtrat). Untuk bobot rata-rata dan panjang maggots terbaik dihasilkan pada perlakuan A (0,20 g/individu dan 1,83 cm/individu), terendah pada B (0,12 g/individu dan (1,58 cm). Jumlah populasi maggots yang terbanyak dihasilkan pada perlakuan B (5.182,31 ind./4 kg subtrat) dan terendah pada D (1.479,44 individu/4 kg subtrat). Nilai biokonversi maggots terhadap bahan organik OSEterbaik (organic substrate efficiency) tertinggi pada perlakuan A (16,84%) dan terendah pada D (5,99%). Secara teknis perlakuan A sedikit lebih baik dari B sedangkan secara ekonomi media subtrat organik terbaik untuk budidaya maggots terdapat pada perlakuan B dengan biaya produksi sebesar Rp. 7.257 dan nilai ECR (economic convertion ratio) sebesar 5.81 lebih rendah dari ke 3 perlakuan lainnya.
 
 Kata kunci: Maggots, black soldier fly, Hermentia illucens, limbah organik.

Pengaruh Formula Pakan terhadap Pertumbuhan Larva Hermetia illucens dalam Biokonversi Limbah Organik

Abstract. The growth rate of Hermetia illucens larvae in the bioconversion of organic waste is influenced by the media and environmental conditions where the BSF lives. This study aims to determine the effect of the feed formula on the growth of Hermetia illucens larvae in the bioconversion of organic waste. This research method was carried out by rearing BSF larvae, making BSF feed formulas, determining larval length, determining the weight and weight of BSF cassava. The results showed that the feeding formula from fish waste, tapioca waste with a chopped diameter of 10,20,30 mm gave a significant effect on the growth of BSF larvae (larval length, larvae weight) and BSF maggots. The provision of 20 and 30 percent fish waste has a higher weight and length with a chopped diameter of 20 and 30 mm..Keywords: feed formula, hermetia illucens, bioconversion, organic waste

Fiber Nanoarchitectonics for Pre-Treatments in Facile Detection of Short-Chain Fatty Acids in Waste Water and Faecal Samples.

Short-chain fatty acids (SCFAs) are among the active metabolites in biological process both in the intestinal tract and the bioconversion of organic wastes, which has resulted in various human diseases and environmental problems. In order to accurately detect SCFAs, we introduced a novel extraction sorbent. Electrospun polyacrylonitrile (PAN) nanofiber membrane was synthesized, then poly (3, 4-Ethylenedioxythiophene) (PEDOT) was deposited onto the surface of electrospun PAN nanofibers by in situ polymerization. The morphology of the composite PAN/PEDOT nanofiber was characterized by scanning electronic microscopy (SEM) and FTIR spectrum. PAN/PEDOT was used to isolate and concentrate the SCFAs in waste water and fecal samples before gas chromatography mass spectrometry (GC-MS) analysis. The analytical method was evaluated systematically, and low limits of detection (LODs) of 0.34–0.87 μg/L and good linearity (R2 ≥ 0.9953) were obtained. The method was applied successfully for the determination of SCFAs in waste water and fecal samples, with good recovery (87.5–104.6%) and satisfactory reproducibility (relative standard deviation: 6.5–14.1%). The results indicated that the proposed method can be used as a potential approach for the determination of SCFAs with high sensitivity in waste water and biological samples.

The case for a wider range of flies for use in waste bioconversion

Bioconversion is the process whereby nutrients are recovered from organic waste products, often by flies, to produce value-added products such as protein for animal feed and lipids for biodiesel production. Currently, research and industry focus on a select few fly species for use in bioconversion that are generalists in their feeding behaviour, the black soldier fly,Hermetia illucens L., and the housefly,Musca domestica L. More investigation is needed on species of flies that are more suited to underutilised waste streams, including meat processing waste. Species of flies that breed in carrion, such as blowflies (Calliphoridae) and flesh flies (Sarcophagidae) can be used to reduce meat processing waste and produce a valuable source of protein. In this review, we propose more investigation and use of a wider range of fly species for bioconversion of organic waste. Four blowfly species are recommended for use in the bioconversion of meat processing waste or a mixture of manure waste and meat processing waste.Chrysomya chloropyga (Wiedemann) is a large mammal carcass specialist and has been found to be effective at recovering nutrients from abattoir waste within four days and producing large larvae in the process.Chrysomya putoria (Wiedemann) andChrysomya megacephala (Wiedemann) naturally breed in carrion and faeces, are associated with pit latrines and respond well under mass rearing conditions, with high egg production. These species would be recommended for a large-scale bioconversion facility that receives mixed waste streams including manure and animal remains.Lucilia sericata is known to produce antimicrobial compounds that assist in wound healing and has been frequently bred and studied and responds well to lab and mass rearing conditions. We recognise the potential obstacles to using alternative species in industrial-scale bioconversion facilities and pose future directions for research to overcome these challenges.

Global population genetic structure and demographic trajectories of the black soldier fly, Hermetia illucens

BackgroundThe black soldier fly (Hermetia illucens) is the most promising insect candidate for nutrient-recycling through bioconversion of organic waste into biomass, thereby improving sustainability of protein supplies for animal feed and facilitating transition to a circular economy. Contrary to conventional livestock, genetic resources of farmed insects remain poorly characterised. We present the first comprehensive population genetic characterisation of H. illucens. Based on 15 novel microsatellite markers, we genotyped and analysed 2862 individuals from 150 wild and captive populations originating from 57 countries on seven subcontinents.ResultsWe identified 16 well-distinguished genetic clusters indicating substantial global population structure. The data revealed genetic hotspots in central South America and successive northwards range expansions within the indigenous ranges of the Americas. Colonisations and naturalisations of largely unique genetic profiles occurred on all non-native continents, either preceded by demographically independent founder events from various single sources or involving admixture scenarios. A decisive primarily admixed Polynesian bridgehead population serially colonised the entire Australasian region and its secondarily admixed descendants successively mediated invasions into Africa and Europe. Conversely, captive populations from several continents traced back to a single North American origin and exhibit considerably reduced genetic diversity, although some farmed strains carry distinct genetic signatures. We highlight genetic footprints characteristic of progressing domestication due to increasing socio-economic importance of H. illucens, and ongoing introgression between domesticated strains globally traded for large-scale farming and wild populations in some regions.ConclusionsWe document the dynamic population genetic history of a cosmopolitan dipteran of South American origin shaped by striking geographic patterns. These reflect both ancient dispersal routes, and stochastic and heterogeneous anthropogenic introductions during the last century leading to pronounced diversification of worldwide structure of H. illucens. Upon the recent advent of its agronomic commercialisation, however, current human-mediated translocations of the black soldier fly largely involve genetically highly uniform domesticated strains, which meanwhile threaten the genetic integrity of differentiated unique local resources through introgression. Our in-depth reconstruction of the contemporary and historical demographic trajectories of H. illucens emphasises benchmarking potential for applied future research on this emerging model of the prospering insect-livestock sector.

Evaluating the potential of okara-derived black soldier fly larval frass as a soil amendment

Bioconversion of organic waste by the black soldier fly (BSF) larva yields a by-product commonly known as ‘frass’. Although BSF larval frass has often been marketed as a biofertilizer, few studies have evaluated this claim. In this study, BSF larvae reared on a pure okara diet achieved an 85% waste reduction in the fresh weight of the okara. Subsequently, the frass was mixed with soil at concentrations of 10, 20, and 30% (vol/vol), and used to cultivate lettuce plants. At 10% concentration, the lettuce plants had biomasses comparable to those of the controls. Higher frass concentrations stunted the growth of the lettuce, likely because of the low C:N ratio of larval frass resulting from the rapid mineralization of nutrients. Larval frass was also found to be able to provide sufficient nutrients for lettuce growth as fertilizer application was only necessary after the first growth cycle, suggesting its suitability as a soil amendment. Analyses of the microbial community of all the growing media showed that the growth medium treatments with BSF larval frass tended to have a lower number of microbial species than the controls. Inherently higher micronutrient levels present in the frass resulted in the growth of lettuce plants. More importantly, the microbial analysis revealed that common foodborne pathogens were absent in the BSF larval frass and elemental analysis also indicated no heavy metal pollutants present. Overall, BSF larval frass was found to be a suitable soil amendment and more in-depth studies could facilitate its sensible use in agriculture.

Bioprocessing of corn rind using continuous multiphase-multistage bioreactor for downstream applications

Corn rind is a major agricultural residue which is often problematic for disposal. However, it is a rich lignocellulose source useful for many downstream industrial applications. The technique commonly used in the bioconversion of organic waste is a static two-stage fermentation system; in the first stage, corn rind is converted to simple sugars, and at the second stage, reduced sugars are used to produce commercial products. The stage one is a resource-consuming process as the product removal is not dynamic, and hence, the bioconversion process comes to an equilibrium due to product accumulation. Therefore, a novel concept of continuous multiphase-multistage bioreactor was introduced, in which the sugars formed are continuously removed to enhance the bioconversion efficiency. A lab-scale model with three digestion modules, each with 2000-ml working capacity, is developed for degradation of corn rind to partially optimize the process parameters that eventually improve corn rind degradation. The multiphase in each stage contributes cumulatively in achieving better degradation of corn rind. In the first stage, out of 150-g feed-stock introduced, a total of 2353 mg of free reducing sugar was released on completion of five phases (1st phase; 431 mg, 2nd phase; 690 mg, 3rd phase; 523 mg, 4th phase; 374 mg, 5th phase; 335 mg) which accounts for 44% of the yield potential. The lab-scale prototype showed promising trend of progressive degradation of corn rind that requires further process optimization to achieve maximum productivity. The reducing sugars thus obtained could be used for subsequent bioconversion processes by using suitable microorganisms.