Growth inhibition and tissue accumulation of palladium in the ubiquitous macrofungus Pleurotus ostreatus (oyster mushroom)

The growth effects and tissue accumulation of palladium (Pd) in the ubiquitous white-rot macrofungus Pleurotus ostreatus (oyster mushroom) are reported. Submerged cultures of P. ostreatus were exposed to Pd (as Na₂PdCl₄) at concentrations of 0, 6.25, 12.5, 25, 50 and 100 mg/L in potato dextrose broth media and incubated for 18 days at 25 °C. The growth response was measured as dried tissue biomass. Relative to controls, growth was partially inhibited at [Pd]_broth = 25 and 50 mg/L. The minimum inhibitory concentration (MIC) of Pd was 100 mg Pd/L. Mean Pd concentrations of dry tissue (± standard error) ranged from 93.5 ± 17.1 mg Pd/kg to 1912.0 ± 293.9 mg Pd/kg, with bioconcentration factors (BCFs) ranging from 16.10 ± 4.17 to 40.91 ± 8.89. A linear positive log-log relationship was found between the C_tissue and [Pd]_broth (R² = 0.476), consistent with a Freundlich isotherm model of sorption. This relationship suggested that physicochemical processes may dominate tissue Pd accumulation in this system rather than biological processes.