Acid-form Sophorolipids Exhibit Minimal Cytotoxicity, Similar to Solvents and Oils Used in Personal Care Products, despite Being Surfactants

Surfactants are amphiphilic substances that induce surface tension reduction, washing, and emulsification and are used for various purposes. Recently, biosurfactants manufactured from renewable resources and with high biocompatibility have gained increasing attention. Sophorolipid (SL), a type of biosurfactant derived from Starmerella bombicola, possesses detergency and emulsification properties, making it suitable for household and personal care applications. However, there are limited toxicological data on SLs. In this study, we conducted cytotoxicity and skin-irritation tests using SLs, revealing that cytotoxicity and skin irritation induced by SLs were extremely low (logIC ₅₀ = 4.76 mg/L) and equivalent to those of solvents and oils used in personal care products.