Aflatoxin B1 Metabolism of Reared Alphitobius diaperinus in Different Life-Stages

Impact of aflatoxin B1-exposure on the genotoxic potential of larval extracts of the black soldier fly (Hermetia illucens), housefly (Musca domestica) and lesser mealworm (Alphitobius diaperinus)

Aflatoxin B1 (AFB1)-contaminated crops could serve as insect feed without affecting growth and survival of black soldier fly (BSFL), housefly (HFL), and lesser mealworm (LMW) larvae. However, the genotoxic safety of larvae reared on AFB1-contaminated substrate remains uncertain. This study assessed the genotoxic effects of larvae reared on 0, 20, and 200 µg/kg AFB1 spiked substrate through in vitro testing. AFB1 and metabolites were analysed in the feed substrate, larvae and residual material using a LC-MS/MS-based method. Cytotoxic and genotoxic potential of larval extracts were assessed using the Ames MPF™ assay (mini-Ames assay), Ames test, and in vitro micronucleus assay. RESULTS: indicated no effect on survival and biomass for all insects and no bioaccumulation of AFB1. Species-specific AFB1 metabolism appeared to occur. HFL exhibited no cytotoxic or genotoxic potential. Further research is required for BSFL and LMW, due to matrix effects and incompatibility with the used in vitro tests.

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.

Mycotoxins on edible insects: Should we be worried?

Edible insects are a solid alternative to meet the growing demand for animal protein. However, there are doubts regarding the safety of insect consumption. Mycotoxins are substances of concern for food safety, as they may cause harmful effects on the human organism and accumulate in the tissues of some animals. This study focuses on the characteristics of the main mycotoxins, the mitigation of human consumption of contaminated insects, and the effects of mycotoxins on insect metabolism. To date, studies reported the interaction of the mycotoxins aflatoxin B1, ochratoxin A, zearalenone, deoxynivalenol, fumonisin B1, and T-2, isolated or combined, in three insect species from Coleoptera and one from Diptera order. The use of rearing substrates with low mycotoxin contamination did not reduce the survival and development of insects. Fasting practices and replacing contaminated substrate with a decontaminated one decreased the concentration of mycotoxins in insects. There is no evidence that mycotoxins accumulate in the tissues of the insects' larvae. Coleoptera species showed high excretion capacity, while Hermetia illucens had a lower excretion capacity of ochratoxin A, zearalenone, and deoxynivalenol. Thus, a substrate with low mycotoxin contamination could be used for raising edible insects, particularly from the Coleoptera order.

Fipronil and fipronil sulfone in chicken: From in vitro experiments to in vivo PBK model predictions

In 2017 a large-scale fipronil contamination in eggs occurred in several European countries. Fipronil and its metabolites have the potential to be transferred into the eggs of laying hens, thereby entering the human food chain. Here, first the metabolism of fipronil was measured in vitro using chicken liver S9. The results show that fipronil is mainly metabolised into fipronil sulfone and the clearance obtained in vitro was extrapolated to in vivo liver clearance. In a second step a physiologically based kinetic model was developed with a focus on fipronil and its major sulfone metabolite and the model outcome was compared to available in vivo data in eggs from the literature. The experimentally obtained clearance was used as model input to evaluate whether such an in vitro-based model can be used in an early phase of a contamination incident to predict the time-concentration curves. Overall, all model predictions were within a 10-fold difference and the estimated elimination half-life for fipronil equivalents was 14 days. In vitro experiments are definitely recommended compared to in vivo studies, since they provide a fast first insight into the behaviour of a chemical in an organism.