[Studies on micelle behaviors of sophorolipid biosurfactant by steady-state fluorescence probe method]

The critical micelle concentration (CMC) of sophorolipid was determined by steady-state fluorescence probe method in which pyrene was used as fluorescence probe. Meanwhile, the changes in the sophorolipid CMC were examined in the addition of NaCl and aliphatic alcohol, respectively. The results showed that the CMC of sophorolipid was 1.3 x 10(-4) mol x L(-1) and had a slight decrease as NaCl concentration increased. However, the CMC of sophorolipid appeared to increase in the presence of aliphatic alcohol. The aggregation numbers and the micelle size of sophorolipid solution were investigated by fluorescence quenching and laser light scattering method. The aggregation numbers were 4-8 with the concentrations of sophorolipid in the range of 4 -8 CMC and the micelle mean diameter for sophorolipid with the concentration of 6 CMC was about 90 nm. These experimental results indicated that the micelle should be incompact.