Dechlorination of 1,2,3- and 1,2,4-trichlorobenzene by the white-rot fungus Trametes versicolor

The degradation of 1,2,3-, 1,3,5- and 1,2,4-trichlorobenzene (TCB) by the white-rot fungus Trametes versicolor was studied. Time course experiments showed a degradation rate of 2.27 and 2.49 nmol d−1 mg−1 dry weight of biomass during the first 4 d of incubation in cultures spiked with 6 mg L−1 of 1,2,3- and 1,2,4-TCB, respectively. A high percent of degradation of 91.1% (1,2,3-TCB) and 79.6 (1,2,4-TCB) was obtained after 7 d. However, T. versicolor was not able to degrade 1,3,5-TCB under the conditions tested. For a range of concentrations of 1,2,4-TCB between 6.5 and 23 mg L−1, a complete dechlorination of the molecule was observed. Cytochrome P450 monooxygenase appears to be involve in the first step of 1,2,4-TCB degradation, as evidenced by marked inhibition of both dechlorination and degradation of 1,2,4-TCB in the presence of the known cyt P450 inhibitors 1-aminobenzotriazole and piperonyl butoxide. Four intermediates formed from 1,2,4-TCB degradation were detected the second day of incubation, which did not appear the seventh day: 2,3,5-trichloromuconate, its corresponding carboxymethylenebutenolide, 2- or 5-chloro-4-oxo-2-hexendioic acid and 2- or 5-chloro-5-hydroxy-4-oxo-2-pentenoic acid. Based on these results, a degradation pathway of 1,2,4-TCB through cyt P450 monooxygenase and epoxide hydrolase was proposed.