Accumulation and distribution of selenium and cesium in the cultivated mushroom Agaricus bisporus — A radiotracer-aided study

The mushroom Agaricus bisporus was cultivated under controlled conditions to follow the simultaneous uptake of selenium and cesium from a mycelium-incubated substrate containing appropriate radiotracers (75Se, 134Cs). Cesium was chosen as a non-complexing cationic marker for tetravalent selenium which tends to undergo biotransformation and/or binding to reactive functional groups in the mushroom. During cultivation it was found that volatile selenium compounds can be adsorbed/absorbed by fruiting bodies. Mushroom homogenates originating from cap and stalk were separated by centrifugation into supernatant and pellet, and the former subjected to size fractionation chromatography. For both cap and stalk the recovery in supernatant was >90% for cesium and ca. 60% for selenium. Cesium gave the expected single cationic peak in the chromatogram whereas for selenium four and five compounds could be observed for stalk and cap, respectively. The extra low molecular weight or inorganic compound in cap might be related to high metabolic activity due to spore formation. The necessity of speciation is clearly illustrated, the more as the toxicity of the separated compounds and their resorption in humans are still to be elucidated.