Rapid copper transfer and precipitation by wood-rotting fungi can effect copper removal from copper sulfate-treated wood blocks during solid-state fungal treatment

• Copper sulfate-treated Japanese cedar blocks were cultivated with wood-rotting fungi.
• Copper was transferred through mycelia away from the wood block.
• Copper oxalate was precipitated on mycelia covering the wood block.
• After the 2-week cultivation, brushing off mycelia removed 42.9% of the copper.
• During the 2-week cultivation, no weight loss of the wood block was observed.

Copper sulfate (CuSO4)-treated Japanese cedar (Cryptomeria japonica) blocks were cultivated with copper-tolerant wood-rotting fungi, either Fomitopsis palustris TYP-0507 or Antrodia xantha Shiga-1F. After 2 weeks, mycelia of both species had covered the blocks, but wood weight loss was not observed. At that time, oxalate accumulations were 21% (F. palustris) and 47% (A. xantha) of their maxima after 6 weeks. Within 2 weeks, the natural copper oxalate complex moolooite appeared at the interface between the wood surface and fungal mat of both species. In addition, the copper content in F. palustris mycelia located far from the CuSO4-treated wood block was at least 5.5 times greater than that in mycelia on untreated controls. By brushing off the moolooite and mycelia, 42.9% (F. palustris) and 34.7% (A. xantha) of the original copper was removed within 2 weeks. The results showed that both species transferred copper from inside the wood blocks and precipitated some of it as moolooite before significant wood decay was observed. Furthermore, F. palustris transferred copper far from the wood blocks, probably through the hyphae. This rapid fungal transfer and precipitation of copper could provide a practical method for the bioremediation of CCA-treated wood.