Introduction. Today, it is well known that mushrooms (pileated fungi, macromycetes) are not only a traditional food, but also an inexhaustible source of substances that have a wide range of pharmacological applications. Some species of mushrooms are considered a source of physiologically important, so-called essential elements, such as Cu, Fe, Zn, Cr, Se, Mo, Mn, etc.
Problem Statement. The biotechnological approaches aiming at enriching the essential elements of the mineral composition of mushroom biomass that is cultivated on a liquid nutrient medium and the fruit bodies of valuable edible species cultivated in the surface culture are relevant and promising, given the mineral composition of macromycetes is rather specific and characterized by a certain selectivity of the accumulation of individual elements from soils / substrates (species-specificity of accumulation). Enrichment with essential elements potentially has to increase the medicinal properties, biological activity, and nutritional value of such mushroom supplements.
Purpose. To identify the bio-accumulative ability of Pleurotus ostreatus (Jacq.) P. Kumm. and P. eryngii (DC.) Quél. mycelial biomass with the compounds of Ge, Se, and Mo.
Materials and Methods. The content of Ge, Se, and Mo in the mycelial biomass of three strains of the Pleurotus genus has been studied by the inductively coupled plasma mass spectrometry (ICP-MS) method during cultivation on a liquid nutrient medium with the addition of germanium, selenium, and molybdenum compounds at a concentration of 10, 25, and 50 mg/l, respectively.
Results. All tested strains have shown a high bio-accumulive ability: for germanium, the coefficients of accumulation are within the range from two to three orders of magnitude (404-3577), for selenium, they vary from one to three orders of magnitude (19-2118), and for molybdenum, they range from one to two orders of magnitude (12-162).
Conclusions. The further development and implementation of mushroom supplements enriched with essential elements should include study of the bioavailability and efficacy of the preparations, as well as biomedical and clinical trials.

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