Everyday life is reliant on the use of petroleum hydrocarbons as a major source of energy. In return their use is responsible for a large proportion of recognised environmental pollution, especially when large spills occur directly into the environment. Crude oil is composed of a wide range of hydrocarbons, and it has come to light that microbes can utilise these compounds as sole carbon sources, dependant on the chemical nature of the hydrocarbons. The biodegradation efficiency of these compounds is due to the enzymes each microbe is capable of producing, along with several other factors such as temperature, pH and nutrient status. Biosurfactants have recently been reported to enhance oil biodegradation and certain microorganisms such as Pseudomonas sp. can produce these compounds (rhamnolipids being the most studied). Therefore the aim of this study was to determine if biodegradation of crude oil occurred by bacteria isolated from soil, to assess the effects of surfactants on crude oil degradation and to investigate rhamnolipid production by P. Stutzeri strain G11 in crude oil samples and crude oil + surfactant samples.
The method involved the isolation of 33 strains of Pseudomonas sp. and 28 Bacillus sp., which were tested for hydrocarbon biodegradation properties. Four strains of Pseudomonas: Pseudomonas stutzeri G11, Pseudomonas putida, Pseudomonas aeruginosa G1 and Pseudomonas fluorescens G6 displayed the highest growth and degradation capabilities, between 42-69%, after 7 days. P. stutzeri was then chosen, due to its high crude oil degradation capabilities, to test the effects of two surfactants (Tween-80 and Trition x100) on crude oil degradation. The results varied between the two surfactants tested illustrating that surfactants can stimulate biodegradation of crude oil; however the degradation is dependent on chemical structure. Finally the amount of the biosurfactant rhamnolipid produced by P. stutzeri was monitored in the presence of 1 and 2.5% crude oil + surfactant. The results showed that rhamnolipid production was found to be higher in 2.5% crude oil and was acclaimed by the authors to be the first report of rhamnolipid production by Pseudomonas sp. in crude oil with surfactant.
The results from this study support the theory that the addition of surfactants facilitates the biodegradation of crude oil, especially in the case of P. stutzeri G11. I believe that this study is a step in the right direction towards fully understanding the biology enabling microorganism to degrade oil. This could lead to an increasingly efficient way to clean up oil pollution from the environment, helping prevent the devastation caused by pollution disasters. I found this paper relatively easy to understand, however I got a little confused at times due to incorrect tenses and plurals used. I also agree with the authors that the next step of research should look into degradation of crude oil and rhamnolipid production under different environmental conditions, so that the research could be applied to different environmental settings accordingly.
Celik, G. Y., Aslim, B., Beyatli, Y. (2008) Enhanced crude oil biodegradation and rhamnolipid production by Pseudomonas stutzeri strain G11 in presence of Tween-80 & Trition x-100. Journal of environmental biology, 29 (6) 867-870.
3 comments:
Hey Arainna. Interesting review. I did one a little while ago about degradation of oil by microbes during spills. The paper partly explored the effects of limited availability of certain inorganic nutrients on the capabilities of microbes. It was expected that as the area was phosphate limited, microbes would have a more minimal and slower rate of response to spills. Therefore, addition of such compounds in similar cases could aid the clean up, instead of using heavy demersents and emulsifiers.
Did your paper mention any factors which might limit the ability of microorganisms to produce these rhamnolipids?
I think you're right - This kind of research is a step in the right direction and could lead to improved responses to spills. So further research into the production of such surfactants under varying conditions could be fundamental.
apparently you can buy rhamnolipids:
Applications
Rhamnolipids are being used in a wide range of applications.
As a surfactant or emulsifier, rhamnolipids can be used as natural “green” ingredient in cosmetics, detergents, shampoos, and soaps, as well as for environmental cleanup (Bioremediation), enhanced oil recovery (EOR), sludge removal, pesticide dispersal and wetting agent. When used as a surfactant, only low concentrations are necessary.
As a fungicide and antibiotic, rhamnolipids can be used as a pesticide, food preservative, and medical device and implant coating.
As a pharmacological agent, rhamnolipids can be used for age marks, bedsores, burn repair, wound healing, psoriasis, sun damage, and wrinkle reduction.
As an anionic complexation agent, rhamnolipid foaming can be used to remove heavy metal contaminants from soils, wastewater, and other liquids.
http://www.rhamnolipid.com/
I have just written a review, again exploring rhamnolipids however it states that these are the most covered form of biosurfactant, do we know why this is? And are there any other biosurfactants that may be better or could 'help' rhamnolipid producng bacteria to degrade oil and further improve our response to oil spills?
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