ABSTRACT
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 (EC50) values of sophorolipids were determined in three aquatic species, and the surface activity of sophorolipids in aqueous solutions was examined at EC50 concentration. Results: The EC50 of sophorolipid surfactant >473 mg l-1 was found in alga Pseudokirchneriella subcapitata, a median lethal concentration (LC50) of 64.8 mg l-1 in fish Oryzias latipes, whereas a high EC50 of 48.2 mg l-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. Key words: Aquatic toxicity, Biosurfactant, Sophorolipid, Surfactant