Tuesday 3 April 2012

Degrading crude oil in the marine environment

Oil spills are an increasing worry for marine ecosystems, especially after the recent BP spill in the Gulf of Mexico. It is known that many marine bacteria, such as Alcanivorax borkumensis, are able to biodegrade oil and other hydrocarbons and these bacteria are often used in clean-up missions. Although there are marine microorganisms that are capable of breaking down the hydrocarbons in crude oil some of the better known microbes used in bioremediation are terrestrial species and most studies have found them to degrade slowly in saline conditions, it is therefore important to investigate whether a micro-organism can still function adequately in high saline conditions before they are used in a marine environment. These organisms degrade more slowly in saline conditions for a number of reasons including: disruption to the cell membrane, the denaturing of proteins and a change in osmotic pressure.

                In this study the ability of Fusarium sp. F092 to degrade three types of crude oil, of two different concentrations, under saline conditions was tested. Agar plugs containing the fungus were added to the different treatments and the degradation of crude oil was determined at 15, 30 and 60 days. There was also a control in which no fungus was added to the treatment.

The compounds which make up crude oil are generally grouped into four fractions depending on their solubility (aliphatics, aromatics, asphaltenes and resins). As the aliphatic fraction is the largest component of fossil fuels the percentage of the crude oil which was composed of aliphatic hydrocarbons was also tested. The fractions of the crude oil were separated using n-hexane and then further separated using chromatography and gas chromatography using helium as the carrier gas.

                The aliphatic fraction of oil type-3 was found to be 75%, which was much higher than types-1 and 2 which was less than 31%. At the lower concentrations of crude oil type-3 was most efficiently degraded (98% of aliphatic fraction) and type-1 was least efficiently degraded (49%). Oil type-2 was about half way between the two (72%). At the higher concentration of crude oil the fungi degraded less than 40% of the aliphatic fraction. It is thought that this decrease in degradation may be due to an increase in toxicity or due to a nutrient or oxygen limitation. It was also found that Fusarium sp. F092 degraded short and long carbon compounds more efficiently than it did intermediate carbon compounds.


Reference: Hidayat, A., & Tachibana, S. (2012). Biodegradation of aliphatic hydrocarbon in three types of crude oil by Fusarium sp. F092 under stress with artificial sea water. Journal of environmental science and technology, 5(1), 64-73.

2 comments:

TASC Madagascar Project said...

Sounds like Fusarium sp. has real potential as a possible alternative in the treatment of marine environments contaminated with crude oil. I like the focus on the aliphatic region showing promise in the development a logical and exciting tool in enhancing oil recovery strategies by targeting the largest component of fossil fuels.

Matt Morgan said...

Ye it does seem that way. There have also been studies investigating promoting the growth of indigenous species, as Theodora has posted about.

http://biol3309.blogspot.co.uk/2012/04/slick-operation-study-of-bacterial.html

It would be interesting to find out which was the best at degrading crude oil as although the indigenous species may degrade it it may not be as fast and Fusarium sp. (an exotic species) may be the better option.