Microbial Load of Cattle Rumen Content and Fruit Waste, and Associated Black Soldier Fly (hermetia Illucens) Larvae

As the search for sustainable protein alternatives and effective waste management solutions grows, Black Soldier Fly Larvae (BSFL) have gained attention for their ability to convert organic waste into valuable biomass. This study investigated the microbial load present in cattle rumen content (CRC), fruit waste (FRW), and a combination of both, used as rearing substrates for BSFL. The objective was to identify fungi and bacteria associated with the substrates and the larvae, in order to assess potential biosafety concerns. Fresh and dried CRC and FRW were processed and analyzed before and after BSFL feeding. Larvae were reared on three treatments: 100% CRC, a 1:1 CRC-FRW mix, and a commercial chicken feed (serving as control), using a Completely Randomized Design (CRD). Findings revealed significant variations in microbial populations across the different treatments. Notably, Saccharomyces spp. was among the fungal species identified, while bacterial isolates included Escherichia coli, Shigella spp., Staphylococcus aureus, and Providencia spp. In general, spent substrates showed higher microbial loads than fresh ones, though the CRC-FRW mix had the lowest fungal count after BSFL feeding. While BSFL possess natural antimicrobial properties, the persistence of some pathogenic microorganisms indicates that thorough hygiene and post-processing measures are essential. Overall, this study underscores the need for routine microbial evaluation when using insect-based systems for waste conversion, particularly if the end products are intended for use in animal feed or as organic fertilizer.