Bioconversion of aflatoxin-contaminated groundnut press cake by larvae of black soldier fly Hermetia illucens results in a complete mass balance for aflatoxin B1

Abstract

Groundnuts are considered as one of the most important cultivated food crops globally. Groundnuts are used for vegetable oil production, which generate a variety of by-products, such as peanut press cake (PPC). Groundnuts are sensitive to infection by aflatoxigenic fungi. Aflatoxins are highly toxic to both humans and livestock, and contaminated crops containing high aflatoxin concentrations are deemed unsafe for consumption and trade. Innovative aflatoxin management strategies are needed and the insect production sector could be such a solution. Larvae of the black soldier fly (BSFL) were exposed to a PPC diet naturally contaminated with aflatoxins. After an exposure lasting eleven days, data on larval survival and biomass were collected. The PPC, BSFL and the residual material were analysed by LC-MS/MS to determine the concentration of eight different aflatoxins. A bio-accumulation factor and a molar mass balance were calculated. BSFL survival and biomass were not affected by exposure to the aflatoxin-contaminated PPC diet. The aflatoxins did not accumulate in the insect body, providing a promising outlook for the safety of rearing insects on aflatoxin contaminated PPC with the purpose of using them as food- and/or feed. Aflatoxin B1 (AFB1) was the dominant compound found in PPC. Formation of aflatoxicol, aflatoxin P1, and aflatoxin M1 occurred and taking these metabolites into account, a complete molar mass balance, thus full recovery, for AFB1 was obtained. This differs from previous studies using artificially spiked substrates in which 17–38% was recovered. This calls for additional studies comparing naturally contaminated with artificially spiked feedstuff.