Abstract:
Contamination of soil with used lubricating oil (ULO) is one of the major environmental issues
worldwide that has not been fully attended. Unsafe disposal of ULO create negative impact on
life on earth due to its major chemical constituents, hazardous polycyclic aromatic hydrocarbons
(PAHs) and toxic heavy metals. Bioremediation, that uses microorganisms is one of the most
promising technologies with increasing demand for the remediation of ULO contaminated soil
and water because pollutants can be degraded efficiently at low cost in an ecofriendly way. The
aim of the present study was to isolate and characterize ULO degrading fungi from ULO
contaminated soil. Ten morphologically distinct fungi were isolated from the rhizosphere of
Crotalaria retus grown in ULO contaminated soil. Briefly, rhizosphere soil was serially diluted
and grown on mineral salt agar (MSA) medium supplemented with 10,000 mg kg-1 of ULO per
plate. The ULO was provided as the sole source of carbon and energy. Isolates with ULO
degradation potential were identified by formation of clear zone surrounding fungal growth. The
two most efficient ULO degrading isolates, RUH 6 and 7 were identified as Fusarium solani and
Aspergillus nidulans respectively, using colony characters and sequencing of internal transcribed
spacer region (ITS) spanning the ITS1, 5.8s and ITS2 regions in the ribosomal RNA operon. The
efficiency of ULO degradation by two isolates were further analyzed by using a gravimetric
method in MS broth medium supplemented with 1g of ULO. Fusarium soani RUH 6 and
Aspergillus nidulans RUH 7 were capable of degrading 73.5% and 76.4% of ULO, respectively.
This study signifies the potential of using Fusarium solani RUH 6 and Aspergillus nidulans RUH 7
isolates for efficient remediation of ULO contaminated soil and highlight future directions for in
vivo application.
