No Use Crying Over Spilt Oil

Microbial bioremediation plays an important role in the removal of pollutants as a result of oil spills in the marine environment. A study by Bovio et al. (2017) focussed on the fungal community of a marine site in the Mediterranean Sea which had been contaminated by an oil spill, as little research has been conducted regarding mycobiota. Different techniques are used for removing oil after spills but these often have economic, ecological and technical drawbacks so it is necessary to find bio-based alternative systems (Zhang et al., 2011). Bacteria and fungi could potentially be used to treat pollutants as they use crude oil as their main carbon source (McGenity et al., 2012). Much like bacteria, fungi have also been found to produce biosurfactants, which reduce surface tension and increase uptake of crude oil (Das & Chandran, 2011). This study aims to better understand the role of fungi in bioremediation.

The samples were collected on the 4^th June 2013 at Gela, Sicily where there had been a recent and persistent oil spill. Several areas of testing were conducted.

Fungal isolation and identification:

Seawater was filtered and strains were cultured for taxonomic identification. Soil dilution plate technique was used for the sediment samples and fungi were classified according to macroscopic and microscopic features and molecular analysis. The water samples had high fungal biodiversity with 67 taxa found and 12 new species identified that were previously discovered in seawater and the sediment samples had 17 taxa and 14 new species. Both sample types were dominated by 94% Ascomyota.

Fungal growth on crude oil:

Fungi were tested for their capability to grow on crude oil (this experiment used Arabian Light). The percentage stimulation was calculated and compared with the controls. All 142 fungi were able to grow but with different efficiencies. In the water samples, 24% were stimulated by crude oil presence; 49% insensitive; 27% inhibited. In the sediment samples, 22% were stimulated; 45% insensitive and 33% inhibited.

Crude oil degradation assay:
4 strains were selected that had been stimulated by crude oil. The capability to degrade oil in liquid cultures was tested using DCPIP colorimetric assay. Fungal development was determined by biomass dry weight. A. terreus was the fastest to degrade. There was a correlation between DCPIP disappearance and crude oil degradation. In this experiment, the fungi expressed enzymes only as a response to crude oil and used it was a source of nourishment because the biomass was found to be significantly higher with the presence of oil. 

This study concluded that fungi have the potential to restore marine environments after being contaminated by oil spills and highlighted the existence of an important living fungi community straight after an oil spill.  As this is the first report on mycobiota bioremediation of an oil contaminated site in the Mediterranean Sea it is a very important study which can form the basis for further research as fungi have been neglected in studies up until now. 21% of species isolated have been reported as present for the first time in the marine environment. Bovia et al. (2017) have highlighted the high capacity of some strains of fungi to degrade oil, using it as their sole Carbon source. P. citereonigrum and A. terreus have been identified as having very high bioremediation potential which requires further analysis and could lead to an effective and natural solution for removing pollutants. This report has presented novel knowledge regarding fungi and can be used to develop biological systems to reduce and improve the effects of future oil spills in the marine environment.

Paper discussed:

Bovio, E., Gnavi, G., Prigione, V., Spina, F., Denaro, R., & Yakimov, M. et al. (2017). The culturable mycobiota of a Mediterranean marine site after an oil spill: isolation, identification and potential application in bioremediation. Science Of The Total Environment, 576, 310-318. http://dx.doi.org/10.1016/j.scitotenv.2016.10.064

Other papers referenced:

Das, N., Chandran, P. (2011). Microbial degradation of petroleum hydrocarbon contaminants: an overview. Biotechnol. Res. Int. 2011, 1–13.

McGenity, T.J., Folwell, B.D., McKew, B.A., Sanni, G.O. (2012). Marine crude-oil biodegradation: a central role for interspecies interactions. Aquat. Biosyst 8 (10), 10–1186.

Zhang, Z., Hou, Z., Yang, C., Ma, C., Tao, F., Xu, P. (2011). Degradation of n-alkanes and polycyclic aromatic hydrocarbons in petroleum by a newly isolated Pseudomonas aeruginosa DQ8. Bioresour. Technol. 102 (5), 4111–4116.