Rhamnolipids are an important class of biosurfactants being explored as greener alternatives to petroleum-based surfactants. These surfactants are generally comprised of a β-hydroxyalkanoyl alkanoate tail glycosylated by one or two rhamnose units, with the most abundant containing a β-hydroxydecanoyl deacanoate tail (Rha-C10-C10 or Rha-Rha-C10-C10). To date, attainable rhamnolipid properties have been limited to those of the biosynthesized materials, which are produced only in small quantities and are costly to harvest and purify. We use a high-efficiency, cost-effective approach to chemical synthesis that allows production of both naturally-occurring and novel rhamnolipids. Chemical synthesis also provides the ability to tailor properties through control of molecular structure. As an excellent example of this ability, a series of monorhamnolipids is highlighted whose combination of tail lengths is selected to vary the molecular shape from cylindrical to conical: Rha-C14-C14, Rha-C14-C12, Rha-C14-C10, Rha-C14-C8, and Rha-C14-C6. In contrast to the expected monotonic change in surfactant properties (e.g. CMC, minimum surface tension, micelle aggregation number) with shape, minima (or maxima) in these metrics are observed across this series of molecules indicating a complex interplay of multiple variables that dictate surfactant properties. These results demonstrate the power of molecular design and chemical synthesis for harnessing the potential of green rhamnolipid surfactants.

Overcoming production limitations of biosynthesis and tailoring rhamnolipid biosurfactant properties through chemical synthesis

249th National Meeting (2015)

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