title: Aqueous gel formation from sodium salts of cellobiose lipids.
abstract: 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 50℃. 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.
authors.affiliation: Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST).
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Imura
authors.forename: Shuhei
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Chikako
authors.initials: C
authors.lastname: Yamashita
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taira
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Minamikawa
authors.forename: Tomotake
authors.initials: T
authors.lastname: Morita
authors.forename: Dai
authors.initials: D
authors.lastname: Kitamoto
mesh_terms: D000935:Antifungal Agents; D002475:Cellobiose / Q000737:chemistry; D003454:Cryptococcus; D005614:Freeze Fracturing; D005782:Gels; D008055:Lipids / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D012212:Rheology; D017670:Sodium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013500:Surface Tension; D013501:Surface-Active Agents / Q000138:chemical synthesis* / Q000737:chemistry; D013696:Temperature; D014867:Water
chemical_list: D000935:Antifungal Agents; D005782:Gels; D008055:Lipids; D017670:Sodium Compounds; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; D002475:Cellobiose