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Team:Nankai
From 2014.igem.org
Overview
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Biosurfactants in MEOR
Microbial enhanced oil recovery (MEOR) is a popular method today in oil production that relies on microorganisms and their metabolic products to mobilize residual oil. Early in 1946 people began to study the application of biosurfactants in oil production, when Zobell discovered that microbe-producing biosurfactants are one of the mechanisms of MEOR. Biosurfactants lower the oil-water interfacial tension, letting the oil droplets release from the sandstones surface, and reduce the viscosity of heavy oil to help its flow. The production of biosurfactants in aerobic environment has been comprehensively researched. Rhamnolipid for instance, has been extensively studied and applied because of its remarkable surface activity and emulsifying properties.
Emulsifying properties of different biosurfactants
Weak(left) Strong(right)
Problems and Solutions
However, until today, it remains at a stage where we have to produce our biosurfactants like rhamnolipid at a bioreactor and then injected them into the oil reservoir. The process of product purification and transportation is very costly and complex, which makes it too unpractical to employ in offshore oil wells. In the meantime, the chance for biosurfactants molecules to meet residual oil along the water pathway is very small. We can’t target the oil droplets separated all over the oil field which is often half wrapped by sandstones. Thus the increase of oil output depends largely on the amount of biosurfactants we pump into the well, causing its low efficiency.
Currently in-situ production of biosurfactants underground is considered advantageous in MEOR. Yet, it is also limited by the oxygen-depleted environments of oil reservoirs because most studied producers are aerobic microorganisms. So clearly, microorganisms that can produce biosurfactants under anaerobic conditions are desperately needed.Why Pseudomonas stutzeri
Among the very few anaerobic biosurfactant-producing microorganisms reported, we selected Pseudomonas stutzeri as our host bacteria. For one reason, we have acquired Pseudomonas stutzeri strains in almost every oil field we studied, indicating its universality. In addition, we want it to produce Rhamnolipid, and Pseudomonas stutzeri is genetically close to Pseudomonas aeruginosa, in which Rhamnolipid ligase genes are highly expressed.
Oil-Water Mixture cultivation
Blank(left) Pseudomonas stutzeri(right)Pseudomonas stutzeri take in oil as their carbon source for living. Thus they would trace down to where an oil droplet is held, and surround it as they grow and multiply. In this way, we sucessfully manage to bring our biosurfactant factories right into the reservoir. And all the nutrition we need to supply is nitrogen in the form of nitrates, which is very cheap and easy to transport.
Why Rhamnolipid
Rhamnolipid is a series of congeners, which may have one or two rhamnoses bonded to β-hydroxy fatty acid with different carbon chain lengths. As we mentioned above, Rhamnolipid has excellent surface activity and terrific emulsifying properties. Moreover, since most of the bacteria like Pseudomonas stutzeri themselves have two uncorrelated synthesis systems of rhamnose and fatty acid, all we have to do is transform the Rhamnolipid ligase genes into bacteria.
Rhamnolipid biosynthetic pathway
Rhamnose Parts(left) Fatty Acid Parts(right)Once it is expressed, it would join the two parts together and give the host bacteria the ability to synthesise Rhamnolipid. Therefore our target genes Rhl ABRI are the key to generate our tiny but enormous underground Rhamnolipid factories.
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Our Results
details
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Our Team
people
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Our Costs
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