Effect of heat treatment on microbiological safety of supermarket food waste as substrate for black soldier fly larvae (Hermetia illucens).

Supermarket food waste, constituting 13% of global food waste, can be upcycled as substrate for black soldier fly larvae (BSFL) and converted into larval biomass. Since presence of food pathogens in supermarket food waste is likely, microbiological safety should be ensured when using waste as insect substrate. Heat treatment provides a suitable pre-treatment to reduce microbiological contaminations. This study investigated the effect of different temperature-time combinations on the microbiological safety of supermarket food waste as BSFL substrate. Artificial supermarket food waste without meat and fish (SFW) was inoculated with both Salmonella and Staphylococcus aureus (7.0log cfu/g) and treated at 50 and 60 °C for 10, 20 and 30 min. While 50 °C was insufficient for adequate pathogen reduction, 60 °C only required 10 min to reduce the Enterobacteriaceae and S.aureus counts to < 1.0logcfu/g and for absence of Salmonella in 25 g. Heat-treated SFW could be stored for two days at ambient temperature or refrigerated without pathogen growth. Treatment of supermarket food waste containing meat and fish at 60 °C for 10 min caused similar results as for SFW, but S.aureus persisted (2.4logcfu/g), possibly by protective effects of fat and/or proteins. Finally, BSFL rearing experiments on SFW revealed significantly higher larval mass, bioconversion efficiency and waste reduction than on Gainesville diet, with no notable differences between untreated and heat-treated SFW. Rearing BSFL on supermarket food waste is possible, and unsafe food waste can be heated to obtain safety without eliminating nutrients necessary for rearing.

Determining the Effect of Different Reproduction Factors on the Yield and Hatching of Tenebrio Molitor Eggs.

Whereas the production of conventional livestock can rely on years of knowledge and experience, the mealworm production industry is still in its early stages. Although the yellow mealworm Tenebrio molitor has been cultivated as feed for pets and zoo animals for quite some time, the optimization of the reproduction process has not been widely explored. For reproduction, beetles are placed in crates supplemented with a substrate to oviposit their eggs. After a specified time, the beetles are removed, and the eggs are further cultivated to develop into larvae. Factors such as oviposition duration and beetle density influence the number of produced mealworms per beetle, partly due to the cannibalistic behavior of the beetles. However, reproductive success has mostly been assessed by determining the number of offspring several weeks after oviposition. As a result, the number of eggs laid and their hatch rates are unknown. In this research, eggs are separated from the oviposition substrate, i.e., harvested. This approach allows to determine the influence of beetle density, oviposition duration, beetle age and the use of a grid during oviposition on the number of eggs produced and the egg hatching rate and timing thereof. In addition, the influence of the harvesting method on the hatching of T. molitor's eggs was determined.

Valorisation Potential of Using Organic Side Streams as Feed for Tenebrio molitor, Acheta domesticus and Locusta migratoria.

Due to increasing welfare and population, the demand for alternative protein sources, obtained with minimal use of natural resources, is rising in today's society. Insects have the potential to be used as an alternative protein source since they are considered to be able to convert low-value biomass into high-value components, resulting in opportunities for valorisation of organic side streams. Moreover, insects are suggested to be a sustainable protein source, referring to the efficient "feed to body" mass conversion potential. The aim of this review was to explore the potential to rear the yellow mealworm (Tenebrio molitor), the house cricket (Acheta domesticus) and the migratory locust (Locusta migratoria) on low or not yet valorised organic side streams within the food supply chain. This was performed by collecting research information focusing on the rearing of the insects in scope on organic biomass. In addition, the nutritional composition of the produced insects as well as their dietary requirements will be reviewed. Finally, the availability of side streams in the EU will be discussed as well as their potential to be used as insects feed.

Isolation and Identification of Dominant Bacteria From Black Soldier Fly Larvae (Hermetia illucens) Envisaging Practical Applications.

This study aimed to establish a representative strain collection of dominant aerobic bacteria from black soldier fly larvae (Hermetia illucens, BSFL). The larvae were fed either chicken feed or fiber-rich substrates to obtain a collection of BSFL-associated microorganisms. Via an approach based on only considering the highest serial dilutions of BSFL extract (to select for the most abundant strains), a total of 172 bacteria were isolated. Identification of these isolates revealed that all bacteria belonged to either the Proteobacteria (66.3%), the Firmicutes (30.2%), the Bacteroidetes (2.9%) or the Actinobacteria (0.6%). Twelve genera were collected, with the most abundantly present ones (i.e., minimally present in at least three rearing cycles) being Enterococcus (29.1%), Escherichia (22.1%), Klebsiella (19.8%), Providencia (11.6%), Enterobacter (7.6%), and Morganella (4.1%). Our collection of dominant bacteria reflects largely the bacterial profiles of BSFL already described in literature with respect to the most important phyla and genera in the gut, but some differences can be noticed depending on substrate, biotic and abiotic factors. Furthermore, this bacterial collection will be the starting point to improve in vitro digestion models for BSFL, to develop mock communities and to find symbionts that can be added during rearing cycles to enhance the larval performances, after functional characterization of the isolates, for instance with respect to enzymatic potential.

RPamide neuropeptides NLP-22 and NLP-2 act through GnRH-like receptors to promote sleep and wakefulness in C. elegans.

Sleep and wakefulness are fundamental behavioral states of which the underlying molecular principles are becoming slowly elucidated. Transitions between these states require the coordination of multiple neurochemical and modulatory systems. In Caenorhabditis elegans sleep occurs during a larval transition stage called lethargus and is induced by somnogenic neuropeptides. Here, we identify two opposing neuropeptide/receptor signaling pathways: NLP-22 promotes behavioral quiescence, whereas NLP-2 promotes movement during lethargus, by signaling through gonadotropin-releasing hormone (GnRH) related receptors. Both NLP-2 and NLP-22 belong to the RPamide neuropeptide family and share sequence similarities with neuropeptides of the bilaterian GnRH, adipokinetic hormone (AKH) and corazonin family. RPamide neuropeptides dose-dependently activate the GnRH/AKH-like receptors GNRR-3 and GNRR-6 in a cellular receptor activation assay. In addition, nlp-22-induced locomotion quiescence requires the receptor gnrr-6. By contrast, wakefulness induced by nlp-2 overexpression is diminished by deletion of either gnrr-3 or gnrr-6. nlp-2 is expressed in a pair of olfactory AWA neurons and cycles with larval periodicity, as reported for nlp-22, which is expressed in RIA. Our data suggest that the somnogenic NLP-22 neuropeptide signals through GNRR-6, and that both GNRR-3 and GNRR-6 are required for the wake-promoting action of NLP-2 neuropeptides.

Corrigendum: the FMRFamide-like peptide family in nematodes.

[This corrects the article on p. 90 in vol. 5, PMID: 24982652.].

The FMRFamide-Like Peptide Family in Nematodes.

In the three decades since the FMRFamide peptide was isolated from the mollusk Macrocallista nimbosa, structurally similar peptides sharing a C-terminal RFamide motif have been identified across the animal kingdom. FMRFamide-like peptides (FLPs) represent the largest known family of neuropeptides in invertebrates. In the phylum Nematoda, at least 32 flp-genes are classified, making the FLP system of nematodes unusually complex. The diversity of the nematode FLP complement is most extensively mapped in Caenorhabditis elegans, where over 70 FLPs have been predicted. FLPs have shown to be expressed in the majority of the 302 C. elegans neurons including interneurons, sensory neurons, and motor neurons. The vast expression of FLPs is reflected in the broad functional repertoire of nematode FLP signaling, including neuroendocrine and neuromodulatory effects on locomotory activity, reproduction, feeding, and behavior. In contrast to the many identified nematode FLPs, only few peptides have been assigned a receptor and there is the need to clarify the pathway components and working mechanisms of the FLP signaling network. Here, we review the diversity, distribution, and functions of FLPs in nematodes.

Metformin promotes lifespan through mitohormesis via the peroxiredoxin PRDX-2.

The antiglycemic drug metformin, widely prescribed as first-line treatment of type II diabetes mellitus, has lifespan-extending properties. Precisely how this is achieved remains unclear. Via a quantitative proteomics approach using the model organism Caenorhabditis elegans, we gained molecular understanding of the physiological changes elicited by metformin exposure, including changes in branched-chain amino acid catabolism and cuticle maintenance. We show that metformin extends lifespan through the process of mitohormesis and propose a signaling cascade in which metformin-induced production of reactive oxygen species increases overall life expectancy. We further address an important issue in aging research, wherein so far, the key molecular link that translates the reactive oxygen species signal into a prolongevity cue remained elusive. We show that this beneficial signal of the mitohormetic pathway is propagated by the peroxiredoxin PRDX-2. Because of its evolutionary conservation, peroxiredoxin signaling might underlie a general principle of prolongevity signaling.

Neuropeptide GPCRs in C. elegans.

Like most organisms, the nematode Caenorhabditis elegans relies heavily on neuropeptidergic signaling. This tiny animal represents a suitable model system to study neuropeptidergic signaling networks with single cell resolution due to the availability of powerful molecular and genetic tools. The availability of the worm's complete genome sequence allows researchers to browse through it, uncovering putative neuropeptides and their cognate G protein-coupled receptors (GPCRs). Many predictions have been made about the number of C. elegans neuropeptide GPCRs. In this review, we report the state of the art of both verified as well as predicted C. elegans neuropeptide GPCRs. The predicted neuropeptide GPCRs are incorporated into the receptor classification system based on their resemblance to orthologous GPCRs in insects and vertebrates. Appointing the natural ligand(s) to each predicted neuropeptide GPCR (receptor deorphanization) is a crucial step during characterization. The development of deorphanization strategies resulted in a significant increase in the knowledge of neuropeptidergic signaling in C. elegans. Complementary localization and functional studies demonstrate that neuropeptides and their GPCRs represent a rich potential source of behavioral variability in C. elegans. Here, we review all neuropeptidergic signaling pathways that so far have been functionally characterized in C. elegans.