Mycotoxins-contaminated wheat matrices bioconversion by Tenebrio molitor larvae (Coleoptera: Tenebrionidae)

Tenebrio molitor is proposed for the valorization of mycotoxins-contaminated substrates no longer usable for other purposes. Larvae were reared on three different wheat matrices (wholegrain flour, shorts and bran) contaminated with different levels of mycotoxins. Nine diets (3 matrices × 3 contamination levels) were assessed. Larval development time, average daily gain (ADG), substrate consumption, survival rate, and the capacity of T. molitor to accumulate and excrete different mycotoxins, through exuviae and frass, were evaluated. Larval development time, ADG, survival rate and substrate consumption were not negatively affected by the mycotoxins, but only by the rearing matrix, depending on the nutritive value. The ability of larvae to excrete DON and its derivatives through exuviae and frass was observed. Within each matrix, DON contamination in larvae increased significantly moving from poorly to highly contaminated ones. Overall, the ratio between the modified form (deoxynivalenol-3-glucoside) and the native one (DON), increased from 7%, in the raw materials, to 101% in the larvae, highlighting their ability to modify this mycotoxin and accumulate it in their body. Larvae accumulated also nivalenol, zearalenone, and enniatins showing a higher concentration in larvae reared on substrates with high level of contamination, while moniliformin was never found in larvae. Overall, the levels of mycotoxins recorded in larvae was always below the current legal limits for livestock feed, thanks to their ability to excrete them through exuviae and frass. These interesting data open new scenarios on the valorization of mycotoxin-contaminated matrices, not suitable for other livestock farming, by means of insects.