PCBs stimulate laccase production and activity in Pleurotus ostreatus thus promoting their removal

Pleurotus ostreatus degrades polychlorinated biphenyls (PCBs) with an increase of laccase activity. Laccases are well known for their detoxifying activity. We show, using reverse transcription polymerase chain reaction and a biochemical assay, that reduction in PCBs (di, tri, tetra, and penta) levels are correlated with an increase in laccase activity. P. ostreatus cultures were obtained from 0 to 30 days in the presence or absence of 7,100 mg/L PCBs (from transformer oil) and a surfactant. After each selected time cultures were withdrawn and remaining PCBs were determined, a maximal removal percentage of PCBs was obtained at 20 (63.5 +/- 2.0) and 30 days (63.8 +/- 4.6) post-induction. Also, the activity of the enzyme was analyzed and it was found to increase at 10 (6.9-fold) and 20 (6.77-fold) days post-induction in the presence of PCBs, as determined by its activity. Taken together, these data suggest that PCBs induce laccase expression and that laccase catalyzes PCBs removal.