Cellobiose lipids (CLs) are asymmetric bolaform biosurfactants, which are produced by Cryptococcus humicola JCM 10251 and have fungicidal activity. In this study, the sodium salts of CLs (CLNa) were prepared to improve aqueous solubility of the CLs, and their surface and gelation properties in aqueous solutions were examined by surface tension, rheology, and freeze-fracture transmission electron microscopy (FF-TEM) measurements. The surface tension measurements revealed that the CLNa have high surface activity: CMC1 and γCMC1 are 0.1 mg/mL and 34.7 mN/m, respectively. It was also found that the CLNa form giant micelles above their CMC, whose average size is 116.6 ± 31.9 nm. Unlike conventional surfactants, the surface tension reduced further with an increase in concentration and the aqueous solution became viscous at the minimum gelation concentration (MGC: 5.0 mg/mL). In rheological studies, the obtained gels proved to be rather soft and their sol-gel temperature was found to be approximately 50C. FF-TEM observation of the gels showed 3D supramolecular structures with an entangled fibrous network. Since the present CLNa aqueous gels have a degree of fungicidal activity, they could be useful for novel multifunctional soft materials applicable to the food and cosmetic industries.
Rheology, surface tension, cellobiose lipid, glycolipid biosurfactant, freeze-fracture transmission electron microscopy (FF-TEM)
NCBI PubMed ID: 25252740Publication DOI: 10.5650/jos.ess14104Journal NLM ID: 101175339Publisher: Tokyo: Japan Oil Chemists Society
Correspondence: Imura T
Institutions: Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, Toyobo Co., Ltd. Tsuruga Institute of Biotechnology, Tsuruga, Fukui, Japan, Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
Methods: dynamic light scattering, TEM, determination of surface tension, MALDI-TOF/MS
Found