Optimum conditions of temperature, salinity and glucose concentration were investigated for squalene production of the strain of Aurantiochytrium sp. 18W-13a, with a high content of squalene. Squalene production by this strain was optimum at 25 degrees C, 25-50% seawater concentration and 2-6% glucose concentration. When this strain was grown in the optimum condition, the squalene content and production of approximately 171 mg/g dry weight and 0.9 g/L. were much higher than that previously reported in thraustochytrids, plants and yeasts, respectively. Therefore, 18W-13a could be used as an alternative source of commercial squalene. (C) 2011 Elsevier Ltd. All rights reserved.