Degradation by white-rot fungi of high concentrations of PCB extracted from a contaminated soil

White-rot fungi are known to degrade a wide variety of recalcitrant pollutants. In this work, three white-rot fungi were used to degrade a mixture of PCBs at high initial concentrations from 600 to 3000 mg/l, in the presence of a non-ionic surfactant (Tween 80). The PCBs were extracted from a historically PCB-contaminated soil. Preliminary experiments showed that Tween 80 exhibited the highest emulsification index of the three surfactants tested (Tergitol NP-10, Triton X-100 and Tween 80). Tween 80 had no inhibitory effect on fungal radial growth, whereas the other surfactants inhibited the growth rate by 75–95%. Three initial PCB concentrations (600, 1800 and 3000 mg/l) were assayed with three fungi for the PCB degradation tests. The extent of PCB modification was found to depend on PCB concentration (P<0.001) and fungal species (P<0.001). PCB degradation ranged from 29 to 70%, 34 to 73% and 0 to 33% for Trametes versicolor, Phanerochaete chrysosporium and Lentinus edodes, respectively, in 10-day incubation tests. The highest PCB transformation (70%) was obtained with T. versicolor at an initial PCB concentration of 1800 mg/l, whereas P. chrysosporium could modify 73% at 600 mg/l. Interestingly, P. chrysosporium was the most effective for PCB metabolization at an initial concentration of 3000 mg/l, and it reduced up to 34% of the PCB mixture. As an overall effect, an increase in the initial PCB concentration led to a decrease in the pollutant degradation, from 57% to 21%. P. chrysosporium and L. edodes accumulated low chlorinated congeners. In contrast, T. versicolor removed both low and high-chlorinated congeners of PCBs.