The effects of biosurfactant rhamnolipid were tested on the production of cellulase and xylanase from Trichoderma viride in solid substrate fermentation (SSF). The effects of rhamnolipid were also compared with those of chemical surfactant Tween 80. The results showed that rhamnolipid at different concentrations enhanced activities of Avicelase, CMCase and cellobiase to different extents. During the peak enzyme production phase, rhamnolipid and Tween 80 increased cellulase activities by 20-50%. However, in the later fermentation phase, the activities of Avicelase and cellobiase in the presence of rhamnolipid were 122.6% and 157.6% higher than those of the control, respectively. Both rhamnolipid and Tween 80 had the pronounced stimulatory effects on xylanase during the peak enzyme production. Rhamnolipid at 0.018% (w/w) gave the highest xylanase activity, which was 119.6% higher than the control. In the whole, the stimulatory effects of rhamnolipid were superior to those of Tween 80. (c) 2006 Elsevier Ltd. All rights reserved.