The physicochemical properties and chemical composition of trehalose lipids produced by Rhodococcus erythropolis 51T7

This study analyzed the chemical and physical properties of a biosurfactant synthesized by Rhodococcus sp. 51T7. The biosurfactant was a trehalose tetraester (THL) consisting of six components: one major and five minor. The hydrophobic moieties ranged in size from 9 to 11 carbons. The critical micelle concentration (CMC) was 0.037 g L−1 and the interfacial tension against hexadecane was 5 mN m−1. At pH 7.4 the glycolipid CMC/critical aggregation concentration (CAC) was 0.05 g L−1 and at pH 4 it was 0.034 g L−1. A phase diagram revealed effective emulsification with water and paraffin or isopropyl myristate. A composition of 11.3–7.5–81.8 (isopropyl myristate–THL–W) was stable for at least 3 months. The HLB was 11 and the phase behaviour of the glycolipid revealed the formation of lamellar and hexagonal liquid-crystalline textures.