Bacillus velezensis EEAM 10B Strengthens Nutrient Metabolic Process in Black Soldier Fly Larvae (Hermetia illucens) via Changing Gut Microbiome and Metabolic Pathways

Abstract

Insects are a potential alternative protein source to solve the food shortage crisis. Previous studies have illustrated that probiotics can improve the substrate conversion efficiency of insects and increase insect protein content. However, the effects of probiotics on insect physiology and nutrient metabolism are still not well understood. Here, the black soldier fly larvae (BSFL), Hermetia illucens (Diptera: Stratiomyidae), was used as a study subject to deeply investigate the specific interaction among a novel probiotic, Bacillus velezensis EEAM 10B (10B), intestinal microbiota, and the host. In this study, the effects of 10B on the survival and physiology of BSFL were first analyzed. It shows that 10B significantly elevated the substrate conversion rate, average dry weight, and protein content of BSFL by 5%, 0.13 g/pc, and 8%, respectively. Then, we assessed the effect of 10B on the microbial community composition in the gut and frass of BSFL using Illumina Miseq sequencing. It shows that 10B significantly altered the microbial composition of the gut, but not that of the frass. Pearson’s correlation analysis further showed that the Bacillus, unclassified_of_Caloramatoraceae, and Gracilibacillus were positively correlated with the survival rate, crude protein content, and substrate conversion rate of BSFL. To further investigate the effect of 10B on host metabolism, metabolic analyses on germ-free BSFL, monobacterial intestinal BSFL, and natural BSFL were also performed. The results proved that 10B (i) played a vital role in the survival of BSFL; and (ii) regulated the amino acid synthetic and metabolic process of BSFL, thus leading to the rise of the protein content of BSFL. In addition, vitamin backfill assays verified that the BSFL survival rate was significantly improved by supplying the germ-free BSFL with riboflavin, which further suggests that 10B determines the survival of BSFL via delivering riboflavin. Overall, this study provides a reference for understanding the comprehensive contribution of a specific probiotic to its host.

Characteristics of Aflatoxin B1 Degradation by Stenotrophomonas acidaminiphila and It’s Combination with Black Soldier Fly Larvae

“…Indeed, insect gut microbiota can be considered an additional organ with fluidity or malleability. The larval intestinal microbiota is a crucial contributor to the BSFL nutrient metabolic process [ 22 ] and helps the host to tolerate heavy metals [ 29 ] and degrade antibiotics [ 30 , 31 ]. Lou et al [ 30 ] identified two bacterial strains— Alcaligenes faecalis GLD-1 and Ochrobactrum intermedium GLD-2—capable of degrading lincomycin from BSFL gut.…”

“…Functional bacteria isolated from the BSFL gut have been found to benefit the growth of BSFL. Pei et al [ 22 ] reported that Bacillus velezensis EEAM 10B could improve the protein synthesis process and digestive enzyme activities in BSFL, thus elevating the substance uptake and protein conversion ability of BSFL. When the intestinal ciprofloxacin-degrading isolates were re-inoculated to the sterile BSFL system, the larvae survival rate and weight were significantly increased in comparison with the sterile BSFL system [ 31 ].…”

“…Germ-free BSFL was constructed as described in our previous study [ 22 ]. Fresh BSFL eggs provided by the BSFL Culturing Center of Henan Agricultural University were placed in a sterile centrifuge tube containing 1 mL of 2.7% NaClO solution and 1 mL of Sporgon (Beijing Mingyangkehua Bio-Technology, Beijing, China) and were shaken gently to disperse the eggs thoroughly.…”

The Use of Probiotics during Rearing of Hermetia illucens: Potential, Caveats, and Knowledge Gaps

“…On the other hand, diets consisting of lignocellulolytic biomass have demonstrated poor conversion into larval mass [ 32 ]. Thus, it is not unexpectedly that materials such as soybean curd residue [ 36 ], rice straw [ 34 ], and peanut shell powder [ 47 ] are included in studies to stimulate insect productivity. At the same time, as summarized in Table 1 , many studies were performed on (chicken) manure as BSFL have been opted as a valuable solution for these types of waste to reduce ecological pollution [ 10 ].…”

Enhanced protein degradation by black soldier fly larvae (Hermetia illucens L.) and its gut microbes

“…BSFL has been used to degrade organic waste. Most of the omics data used to study the changes of gut microbiota composition involve 16S rRNA or 16S rDNA ( Jiang et al, 2019 ; Wynants et al, 2019 ; Zhan et al, 2020 ; Pei et al, 2022 ). Few studies have focused on ITS1 sequence changes.…”