Preparation and characterization of biosurfactant based on hydrophobically modified alginate

Hydrophobic modified alginate (HM-alginate) was synthesized using a low-energy, environment-friendly process in aqueous solution, with sodium alginate and dodecyl glycidyl ether as starting materials. The HM-alginate was characterized using H-1 NMR, and the reaction efficiency was about 40%. The HM-alginate aggregated in solution; the critical micelle concentration (CMC) was determined using surface tension and dynamic light scattering methods. We observed reasonable agreement between the CMC values obtained by the different techniques, and the CMC was 4.0 x 10(-4) g/mL. The zeta-potential of the HM-alginate in aqueous solution was about -82 mV, which is higher than -51 mV of the sodium alginate. Rheology measurements showed that the HM-alginate solution exhibits a Newtonian behavior at all shear rates, whereas the apparent viscosity is very low. The solubility of the liposoluble substance Sudan IV increased significantly with HM-alginate concentration. This result is promising for potential applications of HM-alginate as an ecology-safe material to encapsulate lipophilic substances.