Use of Fungi in the Bioremediation of Crude Oil in Wake of the Deepwater Horizon Oil Spill

Since the 1970’s the amount of worldwide oil spills has decreased from around 24 per year to around 10 per year in 2010. The use of microbes in the bioremediation of crude oil is an attractive alternative to chemical dispersants or physical burning because of the negative impacts on ecosystem function these more conventional methods have. Crude oil consists of paraffinic, cyclo-paraffinic and aromatic hydrocarbons, heavy metal compounds and nitrogen, oxygen and sulphur containing compounds. This complexity in composition gives crude oil a huge range of physiochemical properties that make it extremely difficult to break down. The degradation of oil by fungi is well established, but, with the estimates of fungal diversity estimated at between 1.5 million to 3.5-5.1 million species studies exploring the use of them in oil degradation is merely scratching the surface.

This study by Simister et al (2015) set out to examine fungi isolated from oil soaked sand patties from beaches in the Gulf of Mexico that were affected by the 2010 deepwater horizon spill in order to better understand taxonomic and functional diversity.

 Patties were collected from Gulf shores in 2012 and fungi aseptically transferred to agar plates. For fungal characterisation, DNA was isolated and BLAST searches carried out. Fungi were assessed to determine whether they could utilize crude oil as a sole carbon source and then degradation experiments in triplicate for each species were carried out at 20, 30 or 40˚C. Degradation of individual components of the oil was determined and the results statistically analysed.

Isolates degraded variable quantities of oil (32-65%) with the preferential degradation of short chain n-alkanes (90-99%) and long chain n-alkane degradation even more variable (7-87%). They found a preference for degradation of low molecular weight polycyclic aromatic hydrocarbons (PAH) over high molecular weight PAHs. They found no significant or consistent trends with species at certain temperatures.

This study produces some expected and some possibly new results. The authors further hypothesise that factors such as nutritional status may have a more important impact on the ability of fungi to degrade oil than temperature. They identified 3 species of Ascomycota fungi; Fusarium, Scopulariopsis and Aspergillus all of which are commonly known to degrade petroleum hydrocarbons. This study provides further evidence for the successful use of fungi in the bioremediation of crude oil and provides the basis for further study in the area. It also raises the question of nutritional importance on the impact of crude oil degrading fungi, an interesting area and potential for future study.

Reviewed Paper:

Simister, R.L., Poutasse, C.M., Thurston, A.M., Reeve, J.L., Baker, M.C. and White, H.K., 2015. Degradation of oil by fungi isolated from Gulf of Mexico beaches. Marine pollution bulletin, 100(1), pp.327-333.