Feeding Impact on the Gut Microbiome of Hermetia illucens Larvae

The microbiome of the black soldier fly larvae (BSFL) formed in real rearing substrates in close to industrial conditions was studied. The used substrates, dairy waste and feeding yeasts, differed in the sources of protein, which are available in commercial rearing of the black soldier fly (BSF). Amplicon 16S rRNA sequencing of the BSFL gut metagenome reveals high variability in the microbiome composition. The only bacteria genus found in all the studied developmental stages of BSFL was Enterococcus. We identified typical microorganisms for the initial and final stages of the experiment, as well as typical patterns in changes of the abundance of the main groups of microorganisms. It has been noted that many microorganisms previously believed to be members of the core microbiome of BSFL gut (such as Dysgonomonas) may be completely absent. It is important that the change of rearing conditions influences also the BSFL microbiome: opportunistic pathogen microorganisms, as well as unwanted histamine-poisoning bacteria can appear. Most of them belong to the families Enterobacteriaceae, Morganelliaceae, and Campylobacteriaceae. Other conditions prompt development of spore-forming bacilli, the presence of which may prevent successful heat sterilization of the final product (larva biomass). However, various modifications of substrate composition and the duration of the larva rearing lead to a reduction or complete elimination of unwanted microorganisms.