Molecular Dynamics Simulation of the Oil Sequestration Properties of a Nonionic Rhamnolipid

A detailed molecular
dynamics simulation study is presented on
the behavior of aggregates composed of the nonionic monorhamnolipid
α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate
(Rha-C10-C10) and decane in bulk water. A graph theoretical approach
was utilized to characterize the size and composition of the many
aggregates generated in our simulations. Overall, we observe that
the formation of oil in Rha-C10-C10 aggregates is a favorable process.
Detailed analysis on the surfactant/oil aggregate shows that larger
aggregates are stable. The shape and size of the aggregates are widely
distributed, with the majority of the aggregates preferring ellipsoidal
or cylindrical structures. Irrespective of the decane concentration
in the system, we did not observe free decane in any of the simulations.
Further insights into the binding energy of decane were carried out
using free-energy perturbation calculations. The results showed that
the trapped decane molecules provide stability to the Rha-C10-C10
aggregates of size N = 50 which are shown to be unstable
in our previous study and allow for the growth of larger aggregates
than pure Rha-C10-C10 in water. The density profile plots show that
decane molecules encapsulated inside the aggregate preferred to remain
closer to the center of mass. This study points to the feasibility
of using this biosurfactant as an environmental remediation agent.