Feeding study for the mycotoxin zearalenone in yellow mealworm (Tenebrio molitor) larvae—investigation of biological impact and metabolic conversion

Abstract

Edible insects as additional food and/or feed source may represent one important component to solve the problem of food security for a growing human population. Especially for covering the rising demand for protein of animal origin, seven insect species currently allowed as feed constituents in the European Union are gaining more interest. However, before considering insects such as yellow mealworm larvae ( Tenebrio molitor ) as suitable for, e.g. human consumption, the possible presence and accumulation of contaminants must be elucidated. The present work investigates the effects of the mycotoxin zearalenone (ZEN) and its metabolites on insect larvae. Seven different diets were prepared: toxin-free control, spiked and artificially contaminated (both containing approx.500 μg/kg and approx. 2000 μg/kg of ZEN) as well as two naturally contaminated diets (600 μg/kg and 900 μg/kg ZEN). The diets were used in a multiple-week feeding trial using T. molitor larvae as model insects. The amount of ZEN and its metabolites in the feed, larvae and the residue were measured by HPLC-MS/MS. A significantly enhanced individual larval weight was found for the insects fed on the naturally contaminated diets compared to the other feeding groups after 8 weeks of exposure. No ZEN or ZEN metabolites were detected in the T. molitor larvae after harvest. However, ZEN, α- and β-stereoisomers of zearalenol were found in the residue samples indicating an intense metabolism of ZEN in the larvae. No further ZEN metabolites could be detected in any sample. Thus, ZEN is not retained to any significant amount in T. molitor larvae.

Formation of Zearalenone Metabolites in Tempeh Fermentation

“…However, β-ZEL and its sulfate as well as ZEL-glucosides were not detected in the fermented tempeh-like product. This result is in line with previous results from liquid culture experiments [31] and expecially the absence of β-ZEL shows that the metabolism of the investigated fungi is significantly different from other species such as mammals or insects always forming α-ZEL along with β-ZEL [36,39]. Moreover, all tempeh-like products were also screened for presence of diglucosidic and disulfated derivatives.…”

Impact of Naturally Contaminated Substrates on Alphitobius diaperinus and Hermetia illucens: Uptake and Excretion of Mycotoxins

“…The lack of ZEN uptake in Lesser Mealworm is in agreement with the literature [19], while the possible transferal of DON and FB1 in LM larvae grown on naturally incurred substrates, was observed in this study for the first time.…”

“…However, despite a growing interest, only few papers have addressed the possible uptake and biotransformation of mycotoxins in insects so far [17,18,19,20,21,22]. Although information on the possible biotransformation and/or excretion mechanisms are still scattered, all the studies performed to date consistently demonstrated that parent mycotoxins are not bioaccumulated by insects grown in contaminated substrates.…”

Distribution of T-2 toxin and HT-2 toxin during experimental feeding of yellow mealworm (Tenebrio molitor)

“…Recent studies have shown that insects-if kept on rotten and/or mouldy substrates-may render hazardous metabolites harmless via their own metabolism or largely excrete them, especially mycotoxins, such as zearalenone or type B trichothecenes (Niermans et al 2019;Ochoa Sanabria et al 2019;Van Broekhoven et al 2017). However, as shown for zearalenone, metabolism in T. molitor may also result in the formation of compounds of higher toxicity, such as αzearalenol (Niermans et al 2019). Based on these studies, it could be possible to obtain a safe product for further use for food or feed through insects reared on material no longer suitable for animal or human consumption.…”