Use of spent mushroom compost to bioremediate PAH-contaminated samples

Spent mushroom compost (SMC) is a bulky waste byproduct of mushroom industry and produced abundantly. The SMC of Pleurotus pulmonarius immobilized laccase (0.88 mmoles min−1 g−1) and manganese peroxidase (0.58 mmoles min−1 g−1) of which the optimal temperatures were 45 and 75 °C, respectively. In laboratory test, complete degradative removal of individual naphthalene, phenanthrene, benzo[a]pyrene and benzo[g,h,i]perylene (200 mg PAH kg−1 sandy-loam soil) by 5% SMC was obtained in two days under continuous shaking at 80 °C. The SMC-treated PAH samples had significantly reduced or removed their toxicities as revealed by the Microtox® bioassay. These results were confirmed by gas chromatography–mass spectrometry analysis on the breakdown products. A phthalic derivative which is reported as a degradative product of PAHs by ozonation or ligninolysis was also detected in the SMC-treated samples. The results demonstrate the potential in employing SMC in ex situ bioremediation.