Effect of Rearing Temperature on Growth and Microbiota Composition ofHermetia illucens

The potential utilization of black soldier fly (Hermetia illucens) as food or feed is interesting due to the nutritive value and the sustainability of the rearing process. In the present study, larvae and prepupae ofH. illucenswere reared at 20, 27, and 33 degrees C, to determine whether temperature affects the whole insect microbiota, described using microbiological risk assessment techniques and 16S rRNA gene survey. The larvae efficiently grew across the tested temperatures. Higher temperatures promoted faster larval development and greater final biomass but also higher mortality. Viable Enterobacteriaceae,Bacillus cereus,Campylobacter,Clostridium perfringens, coagulase-positive staphylococci,Listeriaceae, andSalmonellawere detected in prepupae.CampylobacterandListeriaceaecounts got higher with the increasing temperature. Based on 16S rRNA gene analysis, the microbiota of larvae was dominated byProvidencia(>60%) and otherProteobateria(mainlyKlebsiella) and evolved to a more complex composition in prepupae, with a bloom ofActinobacteria,Bacteroidetes, andBacilli, whileProvidenciawas still present as the main component. Prepupae largely shared the microbiota with the frass where it was reared, except for few lowly represented taxa. The rearing temperature was negatively associated with the amount ofProvidencia, and positively associated with a variety of other genera, such asAlcaligenes,Pseudogracilibacillus,Bacillus,Proteus,Enterococcus,Pediococcus,Bordetella,Pseudomonas, andKerstersia. With respect to the microbiological risk assessment, attention should be paid to abundant genera, such asBacillus,Myroides,Proteus,Providencia, andMorganella, which encompass species described as opportunistic pathogens, bearing drug resistances or causing severe morbidity.