The effects of the biosurfactant monorhamnolipid (monoRL) and the chemical surfactant Tween 80 on the degradation of phenol by Candida tropicalis CICC 1463 were studied. Both surfactants impeded the decay in cell concentrations at the beginning of the fermentation and enhanced the cell growth thereafter. They also increased the degradation efficiencies of 500 mg/L phenol from 86.9% in control to above 99.0% for all test concentrations within 30 h. The monoRL could also be degraded by the C tropicalis. These results indicate that the surfactants could diminish the toxicity of phenol to the yeast, increase cell growth and improve phenol removal. The monoRL is better than Tween 80 because of biodegradability. (C) 2010 Elsevier Ltd. All rights reserved.