Читать книгу Biosurfactants for a Sustainable Future - Группа авторов - Страница 67

Origin and composition are the two main factors on the basis of which the classification of biosurfactants has been performed. According to Rosenberg and Ron [46], based on the molecular weight, biosurfactants are categorized into two types. The first one is comprised of those compounds that have low molecular weight compounds with lower surface and interfacial tensions and the second one is comprised of high molecular weight compounds with strong surface binding capacity. The majority of low molecular weight biosurfactants comes under the glycolipids, lipopeptides, and phospholipids category while high molecular weight ones are mainly particulate and polymeric surfactants [47]. Another basis for biosurfactant classification is the presence and type of charge on individual polar moiety. The negatively charged surfactants, i.e. anionic usually have a sulphonate or sulfur group as the chief functional group on their cell surface while positively charged or cationic surfactants mainly possess an ammonium and hydroxyl group. Also, surfactants with a neutral or non‐ionic nature are identified and are the products of a 1, 2‐epoxyethane polymerization reaction. When both positively and negatively charged functional groups are present on the same surfactant molecules, they are identified as amphoteric surfactants [48].