Biodegradation of crude oil and n-alkanes by fungi isolated from Oman
Introduction
Annual worldwide consumption of petroleum hydrocarbons was estimated to be of the order of 1012 US gallons (Prince, 1993). Much of it travels by water at some time and some inevitably spills from tankers and pipelines. Aside from occasional tanker spills due to accidents and routine washings of the storage tanks, two major spills occurred during the last 20 years. IXTOC blew-out in Ciudad del Carmen, Mexico, releasing some 14 × 107 US gallons (Prince, 1993). During the first Gulf War of 1991, 0.5–1 million tons of crude oil has been dumped into the Gulf (Struck et al., 1993), which left 650 km oil polluted Saudi Arabian beaches. Some of the spilled crude oil or storage tanks washings pollute the beaches by the formation of tar balls and render them unusable. Large beach tar balls are formed by coalescing of smaller ones. By the action of waves, they entrap organic and inorganic particles and either settle down or are washed by the wave action to the beaches. Beach tar balls vary from one locality to another. On Muscat coastline, Gulf of Oman, the area around Mina Al-Fahal, Sultanate of Oman, the beach tar ball concentration has been estimated to be among the highest values recorded for any world area (Burns et al., 1987; Oostrdam, 1984). Badawy et al. (1993) and Coles and Al-Riyami (1996) quantified tar balls in Oman.
Fungi come in contact with tar balls from the ocean or beach environment. Snellman et al. (1988) isolated a number of fungi from tar balls including Aspergillus and Penicillium species which were also isolated from petroleum-contaminated soil in Saudi Arabia (Bokhary and Parvez, 1993; Hashem, 1995).
The presence of oil degrading microorganisms such as bacteria and fungi is not restricted to a particular ecosystem and has been found in the Arctic, Antartic and temperate regions but little work has been reported in high temperate ecosystems (Prince, 1993). The ability of microorganisms to utilize hydrocarbons in oil-contaminated environments has been documented (Atlas and Bartha, 1972; Atlas, 1981; Obuekwe et al., 2005; Ashraf and Ali, 2006). The utilization of n-alkanes by fungi and yeast as a sole carbon and energy source has been reviewed (Klug and Markovetz, 1971). Several fungi were found to exhibit greater hydrocarbon biodegradation than bacteria (Cerninglia and Perry, 1973) and thus differ in their abilities to utilize n-alkane and crude oil (Lowery et al., 1968; Nynes et al., 1968; Ahearn and Meyers, 1976; Davies and Westlake, 1979; Snellman et al., 1988; Bokhary and Parvez, 1993). Nevertheless, very few studies have been conducted on the ability of filamentous fungi to utilize pure aliphatic hydrocarbons.
The aims of this study were to isolate fungi that colonize crude oil tar balls on beaches in Oman ;to determine the relative growth of these fungi on crude oil and to measure the growth rate and degradation capacity of specific isolates on different n-alkanes fractions of crude oil and on crude oil. This work will eventually help in bioremediation studies to clean up marine oil spills in an affected environment by the use of endogenous fungal strains with desirable degradative traits. We believe that bioremediation in the form of adding microorganisms to affected areas will play an important role in the future as environmentally safe and cost-effective response to marine oil spills.
Section snippets
Sampling sites and isolation of fungi
Eighty tar balls were collected from Al-Qurum, AL-Hail, Al-Sawadi beaches which are recreational beaches along Muscat coastline, Gulf of Oman during the period 2002–2004. They placed in sterile bags and were transferred to the laboratory. Each tar ball was washed three times with sterile sea water, cut into small pieces and placed onto petri dishes containing malt agar chloramphenicol medium (malt extract 20 g l−1, chloramphenicol 100 mg l−1, agar 12 g l−1, sea water 2 l). Fungi that grew on the
Comparative abilities of some fungi to degrade n-alkanes and crude oil
The abilities of A. niger, A. ochraceus and P.chrysogenum to degrade the n-alkanes tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane and crude Omani oil was studied and were compared. Twenty milliliter of the hydrocarbon-adapted fungal medium (HAF) containing sterile 100 μl of each of n-alkanes (13–18C) and crude oil was prepared in test tubes. The test tubes were inoculated by 0.1 ml spore suspension (1.0 × 106 spores/ml) of A. niger, A. ochraceus and P.chrysogenum
Results
Table 1 shows 10 fungi isolated from tar balls that were capable of growing on 20 liquid HAF medium containing crude oil as a sole source of carbon and energy. These fungi have shown different biodegradation abilities which was assessed by descriptive statistical analysis (Scale of 0–4 where 0 means no growth and 4 good growth). A. niger, A. terreus and P. chrysogenum were the most active crude oil degraders. Thus, they were selected for further studies.
Table 2 shows that A. niger, A. terreus
Discussion
In this study, ten fungi were isolated from tar balls collected from Oman beaches. The genera Aspergillus and Penicillium were the most dominant (Table 1). Similar results were reported by Snellman et al. (1988) who showed that the species of Aspergillus and Penicillium made up 33% and 39%, respectively of fungi on tar balls. In this study, we found that all of the fungal isolates tested were capable of assimilating crude oil and some Aspergillus and Penicillium species were more active than
Acknowledgements
We thank Sultan Qabbos University, Sultanate of Oman for their Research Grant No. B1/96/05, College of Science, and Dr. Michael Barry for his comments and corrections of the manuscript.
References (25)
- et al.
Petroleum-derived hydrocarbon in water, sediment and biota from the Mina Al-Fahal coastal waters
Marin. Pollut. Bull.
(1993) - et al.
Beach tar concentration on the Muscat coastline, Gulf of Oman, Indian Ocean, 1993–1995
Marin. Pollut. Bull.
(1996) - et al.
Utilization of aliphatic hydrocarbons by microorganisms
Adv. Microbiol. Physiol.
(1971) - et al.
growth and hydrocarbon degradation by three desert fungi under conditions of simultaneous temperature and salt stress
Int. Biodeter. Biodegr.
(2005) - et al.
Biodegradation potential of hydrocarbon assimilating tropical fungi
Soil Biol. Biochem.
(1993) - et al.
Fungal degradation of oil in the marine environment
- et al.
Effect of oil (crude petroleum) on the survival and growth of soil fungi
Pakistan Int. J. Biol. Biotechnol.
(2006) Microbial degradation of petroleum hydrocarbons: an environmental perspective
Microbiol. Rev.
(1981)- et al.
Biodegradation of petroleum in seawater at low temperatures
Can. J. Microbiol.
(1972) - et al.
Fungi from petroleum-contaminated Saudi Arabian soils
Arid Soil Research and Rehabilitation.
(1993)
Survey of tar, hydrocarbons and metal pollution in the coastal waters of Oman
Marin. Pollut. Bull.
Crude oil degradation by microorganisms isolated from the marine environment
Zeitsc. Allg. Microbiol.
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