Bioaugmentation of a historically contaminated soil by polychlorinated biphenyls with Lentinus tigrinus

Best overall PCB depletions (33.6 ± 0.3%) and dechlorination (23.2 ± 1.3%) were found after 60 d incubation in the absence of SO where, however, the fungus appeared to exert adverse effects on both the growth of biphenyl- and chlorobenzoate-degrading bacteria and the abundance of genes coding for both biphenyl dioxygenase (bph) and catechol-2,3-dioxygenase. A significant (P < 0.001) linear inverse relationship between depletion yields and degree of chlorination was observed in both augmented and control microcosms in the absence of SO; conversely, this negative correlation was not evident in SO-amended microcosms where the additive inhibited the biodegradation of low chlorinated congeners. The presence of SO, in fact, resulted in lower abundances of both biphenyl-degrading bacteria and bph.The PCB depletion extents obtained in the presence of L. tigrinus are by far higher than those reported in other remediation studies conducted under unsaturated solid phase conditions on actual site soils historically contaminated by Aroclor 1260. These results suggest that the bioaugmentation strategy with the maize stalk-immobilized mycelium of this species might be promising in the reclamation of PCB-contaminated soils. The addition of SO to matrices contaminated by technical PCB mixtures, such as Aroclor 1242 and Delor 103 and characterized by a large preponderance of low chlorinated congeners, might not be advisable.The ubiquitous contamination of terrestrial and aquatic ecosystems by polychlorinated biphenyls (PCBs) has become a matter of increasing concern due to their toxicity and ability to accumulate along the food chain [1]. PCBs theoretically encompass as many as 209 different compounds, generally referred to as congeners, with a number of chlorine substitutions in the biphenyl nucleus varying from 1 to 10. From their first production in the 1930s, until their ultimate ban in the 1990s, the overall PCBs production has been estimated to approximately amount to 1.3 milli