Conversion of mycotoxin-contaminated maize by black soldier fly larvae into feed and fertilizer

Globally, large amounts of various crops such as cereals, oilseeds, nuts and spices are contaminated with mycotoxins during pre-harvest, postharvest handling, processing and/or storage. Mycotoxin contamination results into economic and health issues, and valorisation options of contaminated crops are urgently needed. The aim of this research was to evaluate whether quality feed and fertilizer can be safely produced from naturally mycotoxin contaminated crops using black soldier fly larvae (BSFL, Hermetia illucens L.) under realistic field conditions in East Africa. Naturally mycotoxin contaminated maize (corn; Zea mays L.) was used as a model due its prevalence as food and feed and utilized by BSFL together with local agri-food by-products at a research facility in Rwanda. To assess the influence of the initial maize mycotoxin contamination and maize inclusion, larval diets with three mycotoxin contamination levels and two maize inclusion levels were tested. BSFL were tolerant against the high mycotoxin concentrations (e.g. 99.4 μg aflatoxin B1 kg dry mass-1) as the presence of mycotoxins in the substrate did not affect BSFL mass at harvest. Product safety was assessed by quantifying the presence of 38 common and emerging mycotoxins and metabolites in the maize, substrates and BSFL products (e.g. larvae and frass). The results show that it is possible to produce feed and fertilizer with BSFL considered safe within the European Union and East African legal limits with maize contaminated with mycotoxins typical for East Africa. Thereby, this research works towards the safe recycling of nutrients from mycotoxin contaminated maize within the food system in East Africa and beyond.