Modulation of Atlantic salmon (Salmo salar) gut microbiota composition and predicted metabolic capacity by feeding diets with processed black soldier fly (Hermetia illucens) larvae meals and fractions

Background Black soldier fly (Hermetia illucens) is a promising insect species to use as a novel ingredient in fish feeds. Black soldier fly larvae consists of three major fractions, namely protein, lipid, and exoskeleton. These fractions contain bioactive compounds that can modulate the gut microbiota in fish such as antimicrobial peptides, lauric acid, and chitin. However, it is not certain how, or which fractions of black solider fly would affect gut microbiota in fish. In the present study, black soldier fly larvae were processed into three different meals (full-fat, defatted and de-chitinized) and two fractions (oil and exoskeleton), and included in diets for Atlantic salmon (Salmo salar). Atlantic salmon pre-smolts were fed with these diets in comparison with a commercial-like control diet for eight weeks to investigate the effects of insect meals and fractions on the composition and predicted metabolic capacity of gut microbiota. The gut microbiota was profiled by 16S rRNA gene sequencing, and the predicted metabolic capacities of gut microbiota were determined using genome-scale metabolic models. Results The inclusion of insect meals and fractions decreased abundance of Proteobacteria and increased abundance of Firmicutes in salmon gut. The diets that contained insect chitin, i.e., insect meals or exoskeleton diets, increased abundance of chitinolytic bacteria including lactic acid bacteria and Actinomyces in salmon gut, with fish fed full-fat meal diet showing the highest abundances. The diets that contained insect lipids, i.e., insect meals and oil diets enriched Bacillaceae in fish gut. The fish fed diets containing full-fat insect meal had a unique gut microbiota composition dominated by beneficial lactic acid bacteria and Actinomyces, and showed a predicted increase in mucin degradation compared to the other diets. Conclusions The present results showed that the dietary inclusion of insect meals and fractions can differently modulate the composition and predicted metabolic capacity of gut microbiota in Atlantic salmon pre-smolts. The use of full-fat black soldier fly larvae meal in diets for salmon is more favorable for beneficial modulation of gut microbiota than larvae processed by separation of lipid or exoskeleton fractions.

System development for production of black soldier fly larvae (Hermetia illucens) in small scale, using wild flies

Technological innovation in rural areas guarantees the maintenance and subsistence of rural producers. Additionally, it is mandatory to use strategies aimed at reducing costs in animal production and reducing the environmental impact involved, making it challenging in the current global scenario. Thus, it is necessary to develop new alternative methods of production aimed at small scales, which can be implemented in small properties with reduced capital investment. In this sense, the objective was to describe the development of a system capable of inducing the production of black soldier fly larvae-BSFL (Hermetia illucens) through the attractiveness of egg laying of wild adults. To make the larvae production system, the following were needed: a plastic drum, with a capacity of 200 liters, 10 meters of 8mm silk rope, 1.5 m2 of wire mesh with 25mm x 20mm mesh, 1 m2 3mm x 2mm nylon mesh, plastic faucet for draining the slurry, one meter of 20mm diameter hose, two plastic containers with capacity of 20 liters for collecting the slurry and pre-pupae; besides equipment for cutting and finishing the drum. The System was supplied with organic plant material from daily household disposal, and other plant residues produced on the property. The development of this System can provide great social and economic viability, as it can be implemented in small rural properties for the treatment of organic waste. The mechanism presented good performance for the recycling of organic waste, and also for the production of BSFL, with satisfactory quantity collected daily.

Impact of Heat Treatment on the Microbiological Quality of Frass Originating from Black Soldier Fly Larvae (Hermetia illucens)

Since black soldier fly larvae (BSFL, Hermetia illucens) are being produced at substantial volumes, concomitantly large amounts of the resulting by-product, called frass, are generated. This frass can potentially be applied as valuable plant fertilizer or soil improver. Since frass carries high microbial counts, potentially including foodborne pathogens, safety problems for consumers should be prevented. A heat treatment of 70 °C for 60 min is proposed to reduce harmful organisms in insect frass, based on EU regulations ((EU) No. 2021/1925). This study evaluated for the first time the impact of the proposed heat treatment on BSFL frass. This was done by applying the treatment on uninoculated frass as well as on frass inoculated with Salmonella or Clostridium perfringens at 5.0 log cfu/g. The heat treatment resulted in a reduction (maximum one log-cycle) of total viable counts and did not noticeably reduce bacterial endospores. In contrast, Enterobacteriaceae counts were reduced to below the detection limit (10 cfu/g). Heat treatment of inoculated frass resulted in absence of Salmonella in 25 g of frass and reduction of vegetative C. perfringens to below the detection limit (1 cfu/g). The proposed heat treatment appears to be appropriate to meet the microbiological regulations for insect frass.

Staphylococcus aureus in Substrates for Black Soldier Fly Larvae (Hermetia illucens) and Its Dynamics during Rearing

Given the increasing need for (more sustainable) methods to upcycle organic waste streams, the interest to rear insects, like black soldier fly larvae (BSFL), on such streams is increasing. This study reveals that S. aureus is abundantly present in such waste streams, which might be a point of attention for insect producers.

Addendum to a minimalist revision of Costa Rican Braconidae: 28 new species and 23 host records

Twenty-nine species are treated, most of which have host caterpillar and food plant records, and all but one are new to science. The first host record for the agathidine genus Amputoearinus is given. Gnathopleura josequesadai Sharkey, sp. nov. is reported as a hyperparasitoid of fly larvae, the first such record for the genus. The following new species are diagnosed primarily using COI barcode data; Sharkey is the authority for all: Agathidinae: Aerophilus davidwagneri, Aerophilus fundacionbandorum, Aerophilus nicklaphami, Lytopylus davidstopaki, Lytopylus davidschindeli; Alysiinae: Gnathopleura josequesadai; Braconinae: Bracon andreamezae, Bracon franklinpaniaguai, Bracon rafagutierrezi, Bracon guillermoblancoi, Bracon oscarmasisi, Bracon pauldimaurai, Bracon shebadimaurae, Sacirema karendimaurae; Cheloninae: Chelonus minorzunigai; Homolobinae: Homolobus stevestroudi; Macrocentrinae: Macrocentrus michaelstroudi; Orgilinae: Stantonia gilbertfuentesi; Rhysipolinae: Rhysipolis stevearonsoni; Rogadinae: Aleiodes kaydodgeae, Aleiodes kerrydresslerae, Aleiodes josesolanoi, Aleiodes juniorporrasi, Aleiodes rocioecheverri, Aleiodes ronaldzunigai, Choreborogas jesseausubeli, Triraphis doncombi, and Yelicones mayrabonillae.