Compounds secreted by Cladosporium resinae act as surfactants by self-assembling into a wide variety of 3-D configurations tailor-made for different circumstances when water and oil need to mix.

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So potent are the surfactants (compounds that essentially allow water and oil to mix) in organisms like Cladosporium resinae, that the fungus is able to grow in diesel fuel tanks with water content as low as 0.5%. Survival of water-based creatures in those extremely hydrophobic environments would not be feasible without the self-assembling surfactant compound C. resinae secretes to solubilize oil in water. The sophorolipid biosurfactants produced by C. resinae perform the same tasks as artificial surfactants, but have their own distinct advantages. Besides being non-toxic and biodegradable, the biosurfactants are also structurally suited for adaptability over a broad range of conditions. The adaptability arises from the two basic configurations that this particular biosurfactant can form. One is the common form composed of a head group and tail and the other is a closed ring configuration formed when the tail swings around and attaches to the head group. Depending on the circumstances, the combination of these two forms will self-assemble into a variety of 3-D shapes (spheres, sheets, tubes, etc) that create microscopic water-based or oil-based compartments based on need.

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"Surfactants are used in a wide range of different applications, and currently the large majority of surfactants used are petroleum-based or are from other nonsustainable sources…Biosurfactants are produced by microorganisms, and their surface activity properties are broadly similar to conventional surfactants, resulting in reduced surface/interfacial tension, wetting, and emulsification...[advantages include] lower toxicity, antimicrobial properties, greater biodegradability, better environmental compatibility, high selectivity, specific activity at extreme temperatures, pH, and salinity, and the ability to be produced from renewable feedstocks...the hydrophobic building blocks are fatty acids and fatty alcohols, and the hydrophilic parts are mainly carbohydrates and amino acids/peptides." (Penfold et al. 2011:8867)

"The glycolipids are the best known...biosurfactants. In broad terms, they are formed from carbohydrates, in combination with long-chain aliphatic acids or hydroxyaliphatic acids." (Penfold et al. 2011:8868)

"Unlike conventional surfactants, where the molecular structure can be divided into two clear domains of hydrophobic (chain) and hydrophilic (headgroup) moieties, the hydrophobic acetyl groups of the sophorolipids are attached to the hydrophilic sophorose sugar headgroup, and for the LS molecule, both ends of the fatty acid chain are attached to the sophorose sugar headgroup in a highly bent configuration. (Penfold et al. 2011:8874)

"The unusual molecular structure associated with the lactone ring of the LS sophorolipid component results in an unusual evolution in its self-assembly in aqueous solution....The packing constraints associated with the lactone ring structure of the alkyl chains resulted in the formation of small unilamellar vesicles...At higher concentrations, there was a transformation via a large, flexible unilamellar vesicle phase to a disordered lamellar phase, and there was no evidence of a simple globular micellar phase. In contrast, the AS sophorolipid component forms small globular micelles over a wide concentration range." (Penfold et al. 2011:8876)

Journal article
Solution Self-Assembly of the Sophorolipid Biosurfactant and Its Mixture with Anionic Surfactant Sodium Dodecyl Benzene SulfonateLangmuirJune 6, 2011
Jeff Penfold, Minglei Chen, Robert K. Thomas, Chuchuan Dong, Thomas J. P. Smyth, Amedea Perfumo, Roger Marchant, Ibrahim M. Banat, Paul Stevenson, Alyn Parry, Ian Tucker, I. Grillo

Journal article
Microbial contamination of stored hydrocarbon fuels and its control

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