Exploiting wood rotting fungi as tools to enhance the bioremediation of an artificially polycyclic aromatic hydrocarbon polluted soil.

DI CLEMENTE, N. A.; SAPARRAT, M. C. N.; DEL PANNO, M.T.

Lyon

Conferencia; 14th International Conference on Sustainable Use and Management of Soil, Sediment and Water Resources; 2017

Deltares

Two main groups of fungi belonging to phylum Basidiomycota that attack wood may be distinguished as white (WRF) or brown (BRF) ones. WRF thanks to their extracellular, oxidative enzymes, have ability to degrade lignin as well as cellulose and hemicellulose. BRF degrade cellulose and hemicellulose present in wood after only a partial modification of lignin by a nonenzymatic Fenton-type catalytic system. However, all these wood rotting fungi have several mechanisms to transform and detoxify environmental chemicals. Although they are potential agents in bioremediation strategies for contaminated soils, up to now most of the data available are from axenic cultures, so further work is required to study their capacities in nonsterile soil and taking into account the natural variables and their practice applicability in systems at large-scale or at field. Initially we analysed the ability of the WRF Coriolopsis rigida LPSC 232, Peniophora albobadia LPSC 285, Gelatoporia subvermispora FBCC 313 and Grammothele subargentea LPSC 436 as well as the BRF Gloeophyllum sepiarium LPSC 735 to degrade and tolerate phenanthrene (Phe, 30 mg %) when supplemented to agar (0.8 %) basal medium or one supplemented with carboxymethyl-cellulose (CMC) at 1 %. The isolates LPSC 436 and LPSC 735, which tolerated Phe in a 70 % and 50 % respectively compared to control cultures, showed Phe-degrading capacity. However, the isolate LPSC 735 was the one with higher cellulolytic ability, being unaffected by the presence of Phe. In addition, the coinoculation of the fungi LPSC 436 and LPSC 735 showed a synergistic effect on the degradation of PAHs in agar plate. Then, on a microcosm system containing an artificially contaminated soil with 2500 ppm of Phe and using wheat straw as a fungal carrier and as nutrient sources, the degradative ability of both fungi was analysed, either individually (axenic) and through their coinoculation. An abiotic control was done in parallel using non-inoculated sterile wheat straw. Also the effect of the autochthonous soil microbial community was evaluated through similar microcosms but using either sterilised or non-sterilised soil. After 90 days, a significant removal of Phe was detected in sterile soil microcosms inoculated with LPSC 735. The coinoculated soil showed a delay in the degradation activity, becoming effective after 120 days. Since both fungi were able to decrease Phe levels even in unsterile soil microcosms after 30 days, a synergistic interaction between inoculated fungi and the autochthonous microbiota might be implicated. Although Phe elimination was also delay when the fungi were coinoculated, which was detected after 90 days, the soil microbial community was unable to counter the competition between the inoculated fungi. Based on these preliminary results and applying the same study system, we are now evaluating the total hydrocarbon content and phytotoxicity of an artificially contaminated soil with a petrochemical sludge (100 ppm PAH) at 5 and 10 % (w/w) after 30, 60 and 90 days of the fungal inoculation as well as different enzymatic activities relation to degradative processes.