SAFETY OF BLACK SOLDIER FLY LARVAE: MICROBIAL AND HEAVY METAL RISKS

Abstract

Black soldier fly larvae (BSFL) are considered a sustainable protein source and an effective means of recycling organic waste. They are rich in nutrients, including proteins and lipids, making them suitable for animal feed and potentially for human consumption. In addition to their nutritional benefits, BSFL also have environmental benefits, i.e., reducing waste and greenhouse gas emissions. However, concerns about their safety persist, particularly regarding contamination by pathogenic microorganisms, toxins, and heavy metals. The aim of our study was to investigate the effect of different feedstuffs on heavy metal accumulation and on the microcenosis (Enterobacteriaceae, aerobic bacterial endospores, microscopic filamentous fungi) of BSFL. BSFL were fed four feed treatments (I: egg pasta cooked in whole milk; II: cooked rice with peas; III: poultry feed; and IV: cooked couscous, boiled eggs, and raw carrot peels). The results of our study showed that feed variants significantly affect the microbial safety of BSFL. Using MALDI-TOF, we identified 13 species of family Enterobacteriaceae in BSFL, including facultative pathogenic species Enterobacter cloacae, Klebsiella aerogenes, Klebsiella pneumoniae, Morganella morganii, and Proteus mirabilis. Our research confirmed that BSFL fed different feed variants under experimental laboratory conditions contained heavy metals, including cadmium, copper, manganese, molybdenum, nickel, lead, and zinc. Cadmium concentrations in BSFL ranged from 0.12 to 0.18 mg.kg^-1, with the highest values measured in BSFL in variant IV.