Pb tolerance and bioaccumulation by the mycelia of Flammulina velutipes in artificial enrichment medium

Mushrooms have the ability to accumulate high concentrations of heavy metals, which gives them potential for use as bioremediators of environmental contamination. The Pb2+ tolerance and accumulation ability of living mycelia of Flammulina velutipes were studied in this work. Mycelial growth was inhibited when exposed to 1 mM Pb2+. The colony diameter on solid medium decreased almost 10% compared with the control. Growth decreased almost 50% when the Pb2+ concentration increased to 4 mM in the medium, with the colony diameter decreasing from 80 mm to 43.4 mm, and dry biomass production in liquid cultures decreasing from 9.23 +/- 0.55 to 4.27 +/- 0.28 g/L. Lead ions were efficiently accumulated in the mycelia. The amount of Pb2+ in the mycelia increased with increasing Pb2+ concentration in the medium, with the maximum concentration up to 707 +/- 91.4 mg/kg dry weight. We also show evidence that a large amount of the Pb2+ was adsorbed to the mycelial surface, which may indicate that an exclusion mechanism is involved in Pb tolerance. These results demonstrate that F. velutipes could be useful as a remediator of heavy metal contamination because of the characteristics of high tolerance to Pb2+ and efficient accumulation of Pb2+ ions by the mycelia.