Emulsan has been reported as an emulsion stabilizing amphipathic lipoheteropolysaccharide secreted by the oil-degrading bacterium Acinetobacter venetianus RAG-1. Previously, emulsan was regarded as a single polymer. As a result of developing a new purification process, we have discovered that emulsan is a complex of approximately 80% (w/w) lipopolysaccharide (LPS) and 20% (w/w) high molecular weight exopolysaccharide (EPS). The EPS was purified to 98% (w/w) using tangential flow filtration, Triton X-114 phase extraction, ammonium sulfate precipitation, and hydrophobic interaction chromatography. Several previously reported physical properties of emulsan can be attributed to the LPS fraction, such as charge, fatty acid profile, and solution behavior, while the EPS is responsible for the emulsion stabilization activity. The EPS is believed to be cationic in nature, thus providing an electrostatic binding mechanism for the formation of the emulsan complex.

Since its discovery in the late 1970s, emulsan has been the subject of significant interest for fundamental biosynthesis and structure-function relationships as well as for its potential industrial applications. These studies initially examined the emulsification properties of the compound, while more recent efforts have focused on potential biomedical applications. As a result of this change of focus, it became necessary to more completely characterize the structure of the emulsan molecule and to develop a more reproducible purification process. We review previous studies with emulsan and explain how prior notions were recently shown to be incorrect through the development of a new purification process. More recent genetic modification of the relevant operon is also reviewed. Finally, the potential applications for the new purified polymer will be discussed.

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