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From 2010.igem.org

Hydrocarbon Solubility

Spilled oil spreads rapidly in the environment. However, the hydrocarbons in the oil cannot dissolve in the water and will remain on the water surface or adhere to soil particles (1). Hydrocarbons for example octane only reaches a mole fraction of about 1.5 × 10-7 in water (2). This low solubility makes microbiological degradation hard. Still a wide range of microbes including bacteria, fungi and yeasts are able to consume hydrocarbons (3). Evolution has equipped them with a variety of systems to improve the mass transfer from the hydrophobic phase.

These microorganisms are producing biosurfactants. These proteins increase the surface area of hydrophobic contaminants in soil or water and thus increase their aqueous solubility and consequently their microbial degradation (1). The biosurfactants also enables the organisms to increase the hydrocarbon uptake.

The natural oil degrading bacterium Acinetobacter radioresistens secretes a complex of proteins and polysaccharides that have emulsifying capacity (4). One of the well-known proteins with emulsification activity is AlnA. Even when this protein is produced in another organism like Escherichia coli it still works as an emulsifier (4-5).

To make this specific property available as an interchangeable part, we designed and created the AlnA BioBrick. We also developed an universal emulsification assay, which demonstrated that modified E. coli cells with our BioBrick had emulsifying activity of ? The expressed AlnA was highly effective in solubilizing octane, ca.? g per mg of protein, corresponding to ? molecules of octane per molecule of protein. Unmodified E. coli bacteria had no significant emulsifying or octane-solubilizing activity. The inducible AlnA protein BioBrick is now readily available from the registry.

References

1. Karanth, N.G.K., Deo, P.G. and Veenanadig, N.K. (1999) Microbial production of biosurfactant and their importance. Ferment. Sci. Technol. 77:116-126.
2. Sarraute, S., Delepine, H., Costa Gomes, M.F. and Majer, V. (2004) Aqueous solubility, Henry's law constants and air/water partition coefficients of n-octane and two halogenated octanes. Chemosphere. 57:1543-1551.
3. Head, I.M., Jones, D.M. and Roling, W.F. (2006) Marine microorganisms make a meal of oil. Nature Reviews Microbiology. 4:173-182.
4. Walzer, G., Rosenberg, E. and Ron, E.Z. (2006) The Acinetobacter outer membrane protein A (OmpA) is a secreted emulsifier. Environmental Microbiology. 8:1026-1032.
5. Toren, A., Segal, G., Ron, E.Z. and Rosenberg, E. (2002) Structure--function studies of the recombinant protein bioemulsifier AlnA. Environmental Microbiology. 4:257-261.