Li, X. Y., Mei, C., Luo, X. Y., Wulamu, D., Zhan, S., Huang, Y. P., & Yang, H. (2023).
Dynamics of the intestinal bacterial community in black soldier fly larval guts and its influence
on insect growth and development. Insect Science, 30(4), 947-963.
Black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae), is a prominent insect for the
bioconversion of various organic wastes. As a saprotrophic insect, the BSF inhabits microbe-rich
environments. However, the influences of the intestinal microorganisms on BSF growth and
development are not very clear. In this study, the dynamics of the intestinal bacterial community
of BSF larvae (BSFL) were analyzed using pyrosequencing. Actinobacteria, Bacteroidetes,
Firmicutes, and Proteobacteria were the most prevalent bacterial phyla in the intestines of all
larval instars. The dynamic changes in bacterial community compositions among different larval
instars were striking at the genus level. Klebsiella, Clostridium, Providencia,
and Dysgonomonas were the relatively most abundant bacteria in the 1st- to 4th-instar BSFL,
respectively. Dysgonomonas and Providencia also dominated the 5th- and 6th-instar larvae, at
ratios of 31.1% and 47.2%, respectively.
In total, 148 bacterial strains affiliated with 20 genera were isolated on different media under
aerobic and anaerobic conditions. Among them, 6 bacteria, BSF1–BSF6, were selected for
further study. The inoculation of the 6 isolates independently into germ-free BSFL feeding on an
artificial diet showed that all the bacteria, except BSF4, significantly promoted BSF growth and
development compared with the germ-free
control. Citrobacter, Dysgonomonas, Klebsiella, Ochrobactrum, and Providencia promoted BSF
development significantly by increasing the weight gains of larvae and pupae, as well as
increasing the prepupae and eclosion rates. In
addition, Citrobacter, Klebsiella and Providencia shortened the BSF life cycle significantly. The
results illustrate the promotive effects of intestinal bacteria on BSF growth and development.
Klammsteiner, T., Walter, A., Bogataj, T., Heussler, C. D., Stres, B., Steiner, F. M., ... & Insam,
H. (2021). Impact of processed food (canteen and oil wastes) on the development of black
soldier fly (Hermetia illucens) larvae and their gut microbiome functions. Frontiers in
microbiology, 12, 619112.
Canteens represent an essential food supply hub for educational institutions, companies, and
business parks. Many people in these locations rely on a guaranteed service with consistent
quality. It is an ongoing challenge to satisfy the demand for sufficient serving numbers, portion
sizes, and menu variations to cover food intolerances and different palates of customers.
However, overestimating this demand or fluctuating quality of dishes leads to an inevitable loss
of unconsumed food due to leftovers. In this study, the food waste fraction of canteen leftovers
was identified as an optimal diet for black soldier fly (Hermetia illucens) larvae based on 50%
higher consumption and 15% higher waste reduction indices compared with control chicken feed
diet. Although the digestibility of food waste was nearly twice as high, the conversion efficiency
of ingested and digested chicken feed remains unparalleled (17.9 ± 0.6 and 37.5 ± 0.9 in CFD
and 7.9 ± 0.9 and 9.6 ± 1.0 in FWD, respectively). The oil separator waste fraction, however,
inhibited biomass gain by at least 85% and ultimately led to a larval mortality of up to 96%. In
addition to monitoring larval development, we characterized physicochemical properties of pre-
and post-process food waste substrates. High-throughput amplicon sequencing identified
Firmicutes, Proteobacteria, and Bacteroidota as the most abundant phyla,
and Morganella, Acinetobacter, and certain Lactobacillales species were identified as indicator
species. By using metagenome imputation, we additionally gained insights into the functional
spectrum of gut microbial communities. We anticipate that the results will contribute to the
development of decentralized waste-management sites that make use of larvae to process food
waste as it has become common practice for biogas plants.
Topic: Utilizing canteen food waste as an optimal diet for Hermetia illucens (BSF) larvae.
Research Focus: Investigating the potential of using food waste from canteens as a
sustainable feed source for BSF larvae, comparing its consumption and waste reduction
efficiency with chicken feed, and analyzing the effect of different waste fractions on larval
development.
Key Findings:
1. Food Waste Efficiency: Canteen food waste resulted in 50% higher consumption and
15% higher waste reduction rates for BSF larvae compared to chicken feed.
2. Digestibility: Although the digestibility of food waste was almost double that of chicken
feed, the conversion efficiency of ingested and digested chicken feed remained
significantly higher.
o Conversion Efficiency: Chicken feed (17.9 ± 0.6 ingested, 37.5 ± 0.9 digested);
Food waste diet (7.9 ± 0.9 ingested, 9.6 ± 1.0 digested).
3. Oil Separator Waste: The oil separator fraction of the waste inhibited biomass growth
by 85% and caused larval mortality rates of up to 96%.
4. Bacterial Community: Firmicutes, Proteobacteria, and Bacteroidota were the most
abundant phyla in the food waste. Morganella, Acinetobacter, and Lactobacillales species
were identified as indicator species.
5. Microbial Functions: Metagenome imputation provided insights into the functional roles
of gut microbial communities in BSF larvae.
6. Practical Implications: These findings suggest that BSF larvae could play a role in
decentralized waste-management systems, similar to their use in biogas plants, for
sustainable food waste processing.
Galassi, G., Jucker, C., Parma, P., Lupi, D., Crovetto, G. M., Savoldelli, S., & Colombini, S.
(2021). Impact of agro-industrial byproducts on bioconversion, chemical composition, in vitro
digestibility, and microbiota of the black soldier fly (Diptera: Stratiomyidae) larvae. Journal of
Insect Science, 21(1), 8.
The interest in using byproducts from agro-food industries as a rearing substrate for insects is
increasing rapidly. We investigated the influence of byproducts of vegetal origin (okara—a
byproduct of soy milk production, maize distillers with solubles, brewer’s grains), used as
rearing diet for black soldier fly larvae (BSFL), on the following parameters: biomass
production, substrate reduction (SR), nutritional profile and in vitro digestibility, and larval gut
microbiota. Hen diet was used as a control substrate. The highest larval biomass was collected on
maize distillers, whereas the highest SR was observed on okara. The rearing substrate affected
ash, ether extract, and chitin larval content. The BSFL reared on okara were characterized by a
lower lauric acid content (17.6% of total fatty acids). Diets also influenced in vitro crude protein
digestibility (%) for monogastrics, with the highest values for BSFL reared on maize distillers
(87.8), intermediate for brewer’s grains and okara BSFL, and the lowest for hen BSFL (82.7).
The nutritive value for ruminants showed a lower Net Energy for lactation for BSFL reared on
hen diet than okara and dried maize distillers BSFL. The different byproducts showed an
influence on the larval gut microbiota, with a major bacterial complexity observed on larvae fed
with the hen diet. The neutral detergent fiber concentration of dietary substrate was negatively
correlated with Firmicutes and Actinobacteria relative abundance. Insects valorized byproducts
converting them into high-value larval biomass to be used for feed production. The results
evidenced the effects of the tested byproducts on the measured parameters, underling the
chemical composition importance on the final insect meal quality.
Topic: Impact of Agro-Industrial Byproducts on Black Soldier Fly (BSF) Larvae Growth,
Nutritional Profile, and Gut Microbiota.
Research Focus: Exploring the effects of agro-industrial byproducts as rearing substrates
for BSF larvae, examining their impact on larval biomass production, substrate reduction
(SR), nutritional composition, digestibility, and gut microbiota composition.
Key Findings:
1. Substrate Impact: Various byproducts of vegetal origin, such as okara (soy milk
byproduct), maize distillers, and brewer's grains, were tested as feed for BSF larvae, with
hen feed serving as the control diet.
2. Biomass and Substrate Reduction: The highest larval biomass was achieved using
maize distillers, while okara resulted in the highest substrate reduction.
3. Nutritional Composition: Rearing substrates influenced the ash, ether extract, and chitin
content of the larvae. BSF larvae raised on okara had lower lauric acid content (17.6% of
total fatty acids).
4. Digestibility: In vitro crude protein digestibility for monogastrics was highest in larvae
reared on maize distillers (87.8%), followed by brewer’s grains and okara, with the
lowest values observed in hen diet-fed larvae (82.7%).
5. Net Energy for Ruminants: The nutritive value for ruminants showed that larvae fed
hen diet had lower Net Energy for lactation compared to those fed okara and maize
distillers.
6. Microbiota Complexity: The gut microbiota of larvae was significantly influenced by
the dietary substrate, with higher bacterial diversity in larvae fed the hen diet. The neutral
detergent fiber concentration of the substrate negatively correlated with the relative
abundance of Firmicutes and Actinobacteria.
7. Practical Implications: The study highlights the potential of agro-industrial byproducts
to be converted into valuable larval biomass, emphasizing the importance of chemical
composition in determining the quality of insect meal for feed production.
Eriksen, N. T. (2024). Metabolic performance and feed efficiency of black soldier fly
larvae. Frontiers in Bioengineering and Biotechnology, 12, 1397108.
The black soldier fly (BSF), Hermetia illucens, is used in entomoremediation processes because
its larvae can use a variety of organic residues with high efficiency. However, feed efficiencies
are variable and characterized by uncertainties. Recently developed growth and metabolic
performance models have predicted across different studies that BSF larvae have used 53%–58%
of the feed components they have assimilated, in terms of carbon equivalents, for growth
throughout their lifetime when reared on chicken feed. This is termed their average net growth
efficiency. The remainder of the carbon has been lost as CO 2. However, mass balances made
under similar conditions show that the weight gained by BSF larvae corresponds to only 14%–
48% of the feed substrates removed, indicating substrate conversion efficiency. Both
performance indicators show even greater variability if more feed substrates are considered. Feed
assimilation and growth rates, costs of growth, maintenance, and larval lifespan have been shown
to affect how efficiently BSF larvae convert feed into growth. The differences between average
net growth efficiencies and substrate conversion efficiencies further indicate that feed is often
not used optimally in entomoremediation processes and that the overall yield of such processes is
not determined by larval performance alone but is the result of processes and interactions
between larvae, substrates, microbes, and their physical environment. The purpose of this study
is to illustrate how quantification of the metabolic performance of BSF larvae can help improve
our understanding of the role of the larvae in entomoremediation processes.
Topic: Efficiency of Black Soldier Fly (BSF) Larvae in Entomoremediation Processes
Research Focus: Investigating the metabolic performance of BSF larvae (Hermetia
illucens) and their efficiency in converting various organic residues into biomass during
entomoremediation.
Key Findings:
1. Versatile Feeding: BSF larvae are known for their ability to efficiently utilize a wide
range of organic residues, which makes them valuable in entomoremediation processes.
2. Variable Feed Efficiency: The feed efficiencies of BSF larvae show considerable
variability, with recent models predicting an average net growth efficiency of 53%–58%
when fed a chicken diet. This efficiency refers to the proportion of assimilated feed
components, expressed in carbon equivalents, that contribute to growth throughout the
larvae's lifecycle.
3. Carbon Loss: The remaining carbon is primarily lost as CO2, indicating that not all
ingested feed is effectively converted into larval mass.
4. Substrate Conversion Efficiency: Mass balance studies under similar conditions reveal
that the weight gained by BSF larvae accounts for only 14%–48% of the feed substrates
consumed, reflecting substrate conversion efficiency.
5. Influencing Factors: Factors such as feed assimilation, growth rates, maintenance costs,
and the duration of larval lifespan significantly influence the efficiency of feed
conversion into biomass.
6. Complex Interactions: The discrepancy between net growth efficiency and substrate
conversion efficiency suggests that feed is not always utilized optimally in
entomoremediation processes. Moreover, the overall yield of these processes is not solely
determined by larval performance but is influenced by the interactions among larvae,
substrates, microbes, and their physical environment.
7. Study Objective: This study aims to demonstrate how quantifying the metabolic
performance of BSF larvae can enhance our understanding of their role in
entomoremediation processes, potentially leading to improved efficiencies and outcomes.
Jeon, H., Park, S., Choi, J., Jeong, G., Lee, S. B., Choi, Y., & Lee, S. J. (2011). The intestinal
bacterial community in the food waste-reducing larvae of Hermetia illucens. Current
microbiology, 62, 1390-1399.
The authors hypothesised that degradation of organic compounds by the intestinal bacteria of
BSF larvae played an important role in reduction of food waste and manure and produced
beneficial anti-bacterial/anti-fungal (probiotic) compounds that could improve soil conditions. If
anaerobic bacteria for the enzymes they secrete were analysed, then it could be possible to get a
better idea of the relationship between dominant anaerobic bacteria and their food waste-
reducing activity. Therefore, future studies will screen and identify useful strains and genes
involved in the degradation of organic compounds and analyse more probiotic strains from
optimally fed BSF larvae for their potential use at industrial level.
The bacterial communities in the gut of BSF larvae were represented to depend on three different
nutrient sources. Food waste-fed samples had much more complexity of bacterial species than
the samples fed cooked rice and calf forage (Fig. 3). The cooked rice-fed samples had less
diversity than that of the calf forage group because the nutrients in cooked rice were mainly
carbohydrates. The shared 36 bacterial strains from three diets possibly indicated that BSF larvae
had a unique composition of bacteria as gut microbiota.
Topic: Intestinal Bacterial Community in Black Soldier Fly (BSF) Larvae
Research Focus: Examining the role of the intestinal bacterial community in the food waste
reduction capabilities of BSF larvae (Hermetia illucens) and its potential benefits for soil
health.
Key Findings:
1. Hypothesis on Bacterial Degradation: The authors proposed that the intestinal bacteria
in BSF larvae significantly contribute to the breakdown of organic compounds, which
aids in the reduction of food waste and manure. Additionally, these bacteria produce
beneficial antibacterial and antifungal compounds, which could enhance soil conditions.
2. Anaerobic Bacteria Analysis: The study suggests that analyzing anaerobic bacteria and
the enzymes they secrete may provide insights into the relationship between the dominant
anaerobic bacteria and their efficiency in reducing food waste.
3. Future Research Directions: Future investigations are planned to screen and identify
useful bacterial strains and genes that facilitate organic compound degradation.
Furthermore, there will be an emphasis on analyzing probiotic strains derived from
optimally fed BSF larvae for their potential applications at an industrial level.
4. Nutritional Influence on Bacterial Communities: The research revealed that the
bacterial communities in BSF larvae's guts vary based on their nutrient sources. Samples
fed with food waste exhibited a greater complexity of bacterial species compared to those
fed cooked rice and calf forage.
5. Comparative Diversity: Cooked rice-fed larvae showed less bacterial diversity than
those fed calf forage, likely due to the predominant carbohydrate content in the cooked
rice diet.
6. Unique Gut Microbiota Composition: The study identified 36 shared bacterial strains
across the three diets, suggesting that BSF larvae possess a distinct gut microbiota
composition.
Cifuentes, Y., Glaeser, S. P., Mvie, J., Bartz, J. O., Müller, A., Gutzeit, H. O., ... & Kämpfer, P.
(2020). The gut and feed residue microbiota changing during the rearing of Hermetia illucens
larvae. Antonie Van Leeuwenhoek, 113, 1323-1344.
Larvae of Hermetia illucens, commonly known as black soldier fly, efficiently convert organic
waste into nutrient-rich supplements for different applications. Here we performed a preliminary
experiment to investigate the dynamics of the H. illucens gut microbiota and changes in the
composition of the bacterial community in the residue of the larval feed during rearing. We
furthermore quantified the presence of antibiotic resistance and disinfectant genes in the gut and
feed microbiota during the rearing process to elucidate if rearing leads to a reduction, increase,
and/or transfer of resistance genes from the feed to larvae and vice versa. We found that the gut
and feed residue bacterial communities were distinct throughout the rearing process. The gut
microbiome remained more stable compared to the feed residue microbiome varying in both
bacterial abundance and community structure during rearing. Antibiotic-resistance genes were
present in both, gut and feed residues, with a significant increase in pupae and residue samples
taken at the end of the rearing process. Disinfectant-resistance genes were present in the feed
residue and even increased during the rearing process but were not transferred to the gut
microbiome. We conclude that H. illucens larvae have a stable gut microbiome that does not
change significantly over the course of larval development, whereas bacterial communities in the
feed residue are strongly affected by rearing. If the presence of antibiotics and disinfectants
during rearing, can promote the spread of antibiotic/disinfectant-resistance genes among feed and
larvae needs to be evaluated in further experiments.
Topic: Dynamics of Gut and Feed Residue Microbiota in Black Soldier Fly (BSF) Larvae
Research Focus: Investigating the dynamics of the gut microbiota in Hermetia illucens
larvae and the composition of bacterial communities in their feed residue during the
rearing process, with a particular emphasis on antibiotic and disinfectant resistance genes.
Key Findings:
1. Efficient Waste Conversion: Hermetia illucens, or black soldier fly larvae, are
effective at converting organic waste into nutrient-rich supplements, making them
valuable for various applications.
2. Microbiota Composition Changes: A preliminary experiment aimed to explore the
changes in the gut microbiota of BSF larvae and the bacterial community composition in
the residue of the larval feed throughout the rearing process.
3. Stability of Gut Microbiome: The gut microbiome of BSF larvae was found to be more
stable compared to the microbiome of feed residues. The gut microbiota remained
consistent, while the feed residue microbiota exhibited significant variations in bacterial
abundance and community structure during rearing.
4. Antibiotic Resistance Genes: Antibiotic resistance genes were detected in both the gut
and feed residues. Notably, there was a significant increase in these genes in the pupae
and residue samples collected at the end of the rearing period.
5. Disinfectant Resistance Genes: Disinfectant resistance genes were present in the feed
residue and increased throughout the rearing process. However, these genes were not
found to transfer to the gut microbiome.
6. Implications for Future Research: The study concludes that while the gut microbiome
of BSF larvae remains stable during development, the bacterial communities in feed
residues are heavily influenced by the rearing conditions. Further research is warranted to
evaluate whether the presence of antibiotics and disinfectants during rearing could
promote the spread of antibiotic and disinfectant resistance genes between the feed and
the larvae.
