Research On The Solubilization Behavior Of Alkanes By Rhamnolipid

Biosurfactant can enhance the solubility of hydrophobic organiccontaminant, and it was always use for soil remediation. Enhancedsolubility of hydrophobic organic contaminant can increase the contamiantdegradation by microorganisms. In this paper, we have studied the alkanesenhanced solubility behavior by rhamnolipid.Aqueous rhamnolipid solution, we have found that the critical micelleconcentration of rhamnolipid was effect with the ionic in solution. Fromthis research, the CMC of monorhamnolipid in PBS was150μM.Rhamnolipid can solubilized alkanes in low concentration. Thesolubilized MSR was higher when concentration of rhamnolipid was lower.With different kind of alkanes, the MSR were different. In theconcentration of monorhamnolipid below CMC, MSR of solubilizingalkanes was follow the order: MSRd o d e c a n e＞MSRd e c a n e＞MSRt e t r a a d e c a n e＞MSRh e x a d e c a n e. Solubilization alkanes by dirhamnolipid when concentrationbelow CMC, MSR were follow the order MSRd o d e c a n e＞MSRt e t r a d e c a n e＞MSRh e x a d e c a n e. With the increasing of rhamnolipid concentration, size, Zetapotential and free energy of alkane/rhamnolipid co-aggregates wasdecreasing. Rhamnolipid molecule was search for a structure to lower theirfree energy. Micelles was benefit for the thermodynamic stability of thesystem. As the negatively charged polar carboxyl group was part of therhamnolipid. It was shoulder to shouler as the self-assembling.Electrostatic repulsion was between the polar group. It was the reason ofthe surface curvature was increasing with the increase of rhamnolipidconcentration. And then, the size and Zeta potential of co-aggregates wasdecrease as the increasing of rhamnolipid concentration, also with the freeenergy of system. Enhance solubility of alkanes by dirhamnolipid was thesame with monorhamnolipid. Zeta potential, free energy and size ofalkane/dirhamnolipid co-aggregates was decrease with the increasing ofdirhamnolipid concentration. When the concentration of dirhamnolipidabove CMC these values were tend to stabilized as monorhamnolipid. Solubilizing ability of alkanes by dirhamnolipid with concentration belowCMC was obviously higher than concentration above CMC. Surface excessof dirhamnolipid was increasing as the increase of dirhamnolipidconcentration. Surface curvature was increasing because of the theelectrostatic repulsion. And zeta potential, free energy and size ofalkane/dirhamnolipid co-aggregates was all decreased. Dirhamnolipid wasone more sugar-ring than monorhamnolipid. The co-aggregates ofdirhamnolipid/alkane were size different with monorhamnolipid/alkane.