Objective Effects of applying varieties of microbes and Hermetia illucens larvae on microbial community and physicochemical properties as well as larval population of composting food waste were studied.

Methods Based upon the known ability of Micrococcus luteus, Lactobacillus plantarum, and Bacillus velezensis in enhancing growth performance, antioxidant capacity, and microbiota balance in animals, M. luteus FJAT-25102, L. plantarum FJAT-13772, and B. velezensis FJAT-54560 were combined in the respective volume ratios of 1∶1∶1 for Treatment A, 1∶2∶1 for Treatment B, 1∶1∶2 for Treatment C, and 2∶1∶1 for Treatment D, along with control without the inoculants (CK), in composting kitchen discards. The experimentation was conducted with Stage 1 of fermentation with inoculants followed by Stage 2 of synergistic transformation by adding black soldier fly larvae (BSFL) to the compost. High-throughput sequencing was used to analyze the microbial community at each stage. BSFL survival rate (SR), hundred-larva weight (W100), and larval population, as well as physicochemical properties of the compost, were determined at end of the experiment.

Results In Stage 1 and Stage 2, no significant difference in microbial diversity, but community structure, between the treatment and control composts was observed. On the community structure, Bacillota and Actinomycetota were the dominant phyla, and Anaerococcus the most abundant genus constituting 27.11–40.15% and followed by Aminicella at 7.09–18.79% in the treatment composts in Stage 1. In Stage 2 after BSFL were added, the dominant phyla were Bacillota and Bacteroidota. And the abundance variations at genus level became significant, as Erysipelothrix was most abundant at 12.01% in A2 (Treatment A at Stage 2), Fastidiosipila at 7.76% in B2, Cerasibacillus at 7.87% in C2, and Fastidiosipila at 8.73% in D2. The BSFL SR and W100 under B2. And the W5053, Erysipelothrix, norank_f__Family_XI, and unclassified_f__Lachnospiraceae significantly correlated with the key indicators, including TOC, TN, CF, and W100; whereas Helcococcus and Cerasibacillus negatively correlated with W100.

Conclusion The combined use of 3 inoculants and BSFL significant affected the microbial community and functions played in the composting. Treatment B2 that included M. luteus∶L. plantarum∶B. velezensis in the mixing ratio of 1∶2∶1 was significantly conducive to protein breakdown into polypeptides and/or amino acids facilitating nourishing the BSFL. There appeared to be a practical application for waste management based on the current findings.