Toxicity Testing by the Microbial Assay for Risk Assessment (MARA) in Relation to Trace Elements Content in King Bolete (Boletus edulis) Collected in Several Sites of Poland

Boletus edulis (King bolete) is one of the most consumed wild mushrooms on a global scale, but this is particularly the case in Poland. Several studies have reported that mushrooms accumulate many potentially toxic elements (PTEs) such as Hg, Pb, and Cd, which may lead to adverse effects. Therefore, in this preliminary study, an assessment of the potential of a microbial assay for risk assessment (MARA) for ecotoxicological testing of both dried samples of fruiting bodies of King bolete collected from several sites of Poland and water extracts of mushrooms being tested were analyzed. An evaluation of MARA response in Boletus edulis extracts was performed to identify their toxicity and then, using the same samples, instrumental determination of 10 elements (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn) was performed. In general, the MARA responses indicated that the samples were only slightly toxic or nontoxic. Similarly, most of the PTEs were not detected in all dried samples of the fruiting bodies of King bolete. However, the analysis of digested samples (total content) proved that the elements’ content in water extracts was markedly lower than in dried fruit bodies. It implies that the MARA test corresponded better to the elements that are well extracted in water. Therefore, the MARA system can be applied for toxic identification if the targeted toxin is highly extracted in water. Further and more detailed research is still needed to develop reliable approach in order to evaluate the ecotoxicity in food-related bio-based raw materials using the MARA assay.