Awareness of chemical hazards in edible insects: toxicokinetics of mercury in Tenebrio molitor

• Autor(a) principal: Fernandes, André Vinhas Mendes
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33459
• topic: Bioaccumulation; Food exposure; Growth; Contaminants uptake; Safety; Food safety; Contaminants elimination

The human population is increasing significantly, and, as a result, there is a growing demand for an alternative protein source to relieve the pressure from the livestock sector. Discussion regarding edible insects has grown in the scientific community since the report concerning its use as food and feed, from the Food and Agriculture Organization of the United Nations in 2013. The Yellow mealworm larvae (Tenebrio molitor) is considered one of the best solutions to feed pets, livestock and poultry sectors, and human consumption. When reared in agricultural leftovers, mealworms convert waste into valuable nutritional material, reducing waste and contributing to a more sustainable planet. One of the major concerns on rearing insects as a food source is related to food safety aspects. Contaminants can be uptaken by insects through the substrate they feed on, entering into the farming cycle and, consequently, into the food chain. Understanding these compounds’ pathways and their effects on insects and generations’ and different development stages is crucial for the continuous farming production process. After looking at previous studies where mercury was observed to accumulate in edible insect species, this thesis aimed to apply an innovative and more complex approach to understand how mercury is uptaken and eliminated by insects. Considering that, this thesis aimed to investigate the toxicokinetics of Hg in T. molitor larvae exposed through food. This thesis combined a series of ecotoxicological and bioaccumulation assays with previous biomass gain experiments, followed by the Hg bioaccumulation assays. To assess the optimal medium of exposure and larval stage for the bioaccumulation studies, biomass gain experiments were carried out: two larval stages (20-40 mg and 60-80 mg) were exposed to four treatments for 21 days: with soil and oat; with soil only (no oat); with oat only (no soil); no soil and oat. Results revealed a high mortality rate in the treatments where insect larvae growth in soil (with presence of fungi), contrasting with a very low mortality rate and highest biomass gain when both larval stages were exposed to oat and no soil as a substrate. Considering this, the bioaccumulation studies were conducted only with oat (no soil present), using larvae with 60-80 mg, which presented the highest biomass gain, being also the most suitable size from the perspective of the producers. Bioaccumulation experiments consisted of an uptake and elimination phase of 21 days each, providing Hg contaminated and “clean” oat in each phase, respectively. A first-order one-compartment model had the best fit, to explain the uptake and elimination of Hg, in Tenebrio molitor. Through this, it was observed that Hg stays in the organism (Fi=0.682) even after an elimination period in clean oat. In addition, this model had an uptake (k1) and elimination (k2) constant of 0.056 and 0.316, respectively. Lastly, to the best of our knowledge, this was the first time that the absorption and elimination rate were measured through time. To conclude, these experiments should be conducted without soil and toxicokinetic models are a viable method to comprehend the behavior of Hg in mealworms.