Aromatic Hydrocarbon Degrading Phyllosphere Fungi

Abstract

Ambient air contains high amounts of potentially genotoxic and carcinogenic aromatichydrocarbons (AH) that originate from the petroleum related activities and coal refiningprocesses. The potential of phyllosphere organisms to oxidize these compounds into nontoxicforms has been investigated in some recent studies. This study was carried out to investigatethe presence of aromatic hydrocarbon degrading fungi in the phyllosphere of Ixora sp.,Amaranth sp., Hibiscus sp. and Ervatamia sp. which are common on roadsides close to the oilrefinery at Sapugaskanda and in several urban areas having high level of vehicular emission.Their ability to degrade the AHs phenanthrene, naphthalene, xylene and toluene wasinvestigated.

Leaf samples of the four plant species were collected from five areas namely Kollonnawa,Sapugaskanda, Orugodawattha, Panchikawattha and Maradana. Then Phyllosphere fungiwere isolated into pure cultures on Czapek-Dox medium using pour plate method andidentified up to the genus level. Plate assays and spectrophotometric analysis were used toevaluate phenanthrene, naphthalene, xylene and toluene degradation ability of them as thesole source of carbon. The best fungal AH degraders were selected for furthercharacterization and identification.

Isolated phyllosphere fungi, Penicillium spp, Aspergillus spp and Trichoderma spp were ableto degrade phenanthrene, naphthalene, toluene and xylene. Penicillium janthinellum wasfound to be the most effective in degrading naphthalene and phenanthrene with 98.85% and84.83% efficiency respectively. Moreover, Aspergillus niger has the highest toluenedegradation ability. The best xylene degrader; Aspergillus flavus, utilised 57.35% of xylenein the medium. Initial experiments indicated that the highest degradation of aromatichydrocarbons occurs after seven days. Therefore, in all these experiments, isolated fungalspp. were incubated for seven days in media supplemented with aromatic hydrocarbons.

While traditional chemical and physical remediation techniques are currently becoming lesseffective from environmental and economical point of view, there is an increasing interest inbioremediation. According to the finding of the present investigation Penicillium spp. andAspergillus spp. are having the potential to be used in effective bioremediation strategies inthe removal of AH. Their ability to degrade these compounds while surviving underenvironmental stresses makes them suitable candidates for bioremediation.