Induction of hydroxyl radical production in Trametes versicolor to degrade recalcitrant chlorinated hydrocarbons

Extracellular hydroxyl radical (OH) production via quinone redox cycling in Trametes versicolor, grown in a chemically defined medium, was investigated to degrade trichloroethylene (TCE), perchloroethylene (PCE), 1,2,4- and 1,3,5-trichlorobenzene (TCB). The activity of the enzymes catalyzing the quinone redox cycle, quinone reductase and laccase, as well as the rate of OH production, estimated as the formation of thiobarbituric acid reactive substances (TBARS) from 2-deoxyribose, increased rapidly during the first 2–3 days and then remained at relatively constant levels. Under quinone redox cycling conditions, TCE degradation was concomitant to TBARS production and chloride release, reaching a plateau after 6 h of incubation. Similar results were obtained in PCE, 1,2,4- and 1,3,5-TCB time course degradation experiments. The mole balance of chloride release and 1,2,4-TCB and TCE degraded suggests that these chemicals were almost completely dechlorinated. Experiments using [13C]-TCE confirmed unequivocal transformation of TCE to 13CO2. These results are of particular interest because PCE and 1,3,5-TCB degradation in aerobic conditions has been rarely reported to date in bacterial or fungal systems.