Characterization and micellization of rhamnolipidic fractions and crude extracts produced by Pseudomonas aeruginosa mutant MIG-N146.
Two representative rhamnolipidic fractions, RL-F1 and RL-F2, produced by the P. aeruginosa mutant strain MIG-N146, were separated and chemically characterized by TLC, HPLC-MS, and FTIR. The RL-F1 fraction is predominantly mono-rhamnolipid homologues with a high content of one or two fatty acid moieties. The RL-F2 fraction is mainly composed of di-rhamnosyl moieties with two hydrophobic tails. Micellization behavior was investigated to assess the physicochemical properties of the surfactants, RL-F1, RL-F2, and crude rhamnolipidic extracts. The variations in morphology of micelle formation and growth were examined by dynamic light scattering measurements as a function of surfactant concentration. Critical micelle concentration (CMC), average minimal surface tension (gamma(CMC)), saturated surface excess (Gamma(m)), mean surface area per molecule (S), and adsorption efficiency (pC(20)) were determined from the surface tension profiles and compared for the three surfactant systems. It was found that micelle growth was significantly enhanced by increasing rhamnolipid bulk concentration, which was most probably accompanied with an aggregate shape transition. Well-separated multi- or bi-modal distributions of particle size were observed in RL-F2 and the crude extracts solutions. The results of this study demonstrate that molecular architecture of different surfactant compositions profoundly influences the performance of rhamnolipidic surfactants.
Guo
Yan-Ping
YP
College of Environmental Science & Engineering, South China University of Technology, Guangzhou 510006, China.
Hu
Yong-You
YY
Gu
Roy R
RR
Lin
Hui
H
D002851:Chromatography, High Pressure Liquid; D045424:Complex Mixtures; D006017:Glycolipids / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D009154:Mutation / Q000235:genetics*; D010316:Particle Size; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000235:genetics*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
D045424:Complex Mixtures; D006017:Glycolipids; D008823:Micelles; C418382:rhamnolipid