Directional Changes in the Intestinal Bacterial Community in Black Soldier Fly (Hermetia illucens) Larvae

SIMPLE SUMMARY: The black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae), is renowned for its bioconversion of organic waste into a sustainable source of animal feed. Gut microbes play an essential role in aiding their host during the digestion of complex substrates by possessing metabolic properties that the insect lacks. Microbes that survive the gut passage are candidates for microbes that contribute more to larval development, besides just being a nutrient source. Insect larvae cohabit in some form of symbiosis with microbes. Here, a preliminary experiment was performed to explore the dynamics of the H. illucens gut microbiota and the changes in the composition of the bacterial community in organic waste with six different functional strains of the larval feed during rearing. The results showed that the increase in the abundance of Lysinibacillus in the experimental group that was exposed to Lysinibacillus sphaericus was significantly different to the other groups (p < 0.05). The results indicate that H. illucens larvae have a stable gut microbiome that does not change significantly during larval development, whereas bacterial communities in the feed residue with the addition of certain bacteria can be slightly affected by rearing. ABSTRACT: Black soldier fly (BSF) larvae, Hermetia illucens (Diptera: Stratiomyidae) have emerged as an efficient system for the bioconversion of organic waste. Intestinal microorganisms are involved in several insect functions, including the development, nutrition, and physiology of the host. In order to transform the intestinal bacterial community of BSF directionally, six different potential functional strains (Lysinibacillus sphaericus, Proteus mirabilis, Citrobacter freundii, Pseudocitrobacter faecalis, Pseudocitrobacter anthropi, and Enterococcus faecalis) were added to aseptic food waste, and aseptic food waste was used without inoculants as a blank control to evaluate the changes in the intestinal microbiota of BSF under artificial intervention conditions. These six strains (which were isolated from the larval intestinal tract in selective media and then identified and screened) may be considered responsible for the functional characteristics of larvae. The results imply that the increase in the abundance of Lysinibacillus in the experimental group that was exposed to Lysinibacillus sphaericus was significantly different to the other groups (p < 0.05). The results revealed that it is feasible to transform the intestinal microbiota of BSF directionally; there are differences in the proliferation of different strains in the intestine of BSF.