Low toxicity and high surface activity of sophorolipids from Starmerella bombicola in aquatic species: A preliminary study

Aim : This study was carried out to evaluate aquatic toxicity and surface activity of sophorolipids extracted from yeast Starmerella bombicola. Methodology: The half maximal effective concentration (ECJ values of sophorolipids were determined in three aquatic species, and the surface activity of sophorolipids in aqueous solutions was examined at ECS0 concentration. Results : The ECS0 of sophorolipid surfactant >473 mg I'1 was found in alga Pseudokirchneriella subcapitata, a median lethal concentration (LCJ of 64.8 mg I'1 in fish Oryzias latipes, whereas a high ECS0 of 48.2 mg I'1 was noted in crustacean Daphnia magna, respectively. Sophorolipids effectively reduced the aquatic surface tension to 39 mN m'1 in O. latipes and to 41 mN m'1 in D. magna. Interpretation : These results show that sophorolipids from S. bombicola are a promising biosurfactant with an ideal balance of low aquatic toxicity and high surface activity.