The process involved in lignite degradation/solubilization by Penicillium decumbens P6 was studied. P6 secreted some unknown alkaline substance and increased the pH of the medium as it grew. Meanwhile, it excreted some surfactants that might be involved in lignite degradation. The most important aspect in this study was that P6 could excrete some extracellular enzymes that might participate in the lignite degradation. With the induction of lignite, the activities of peroxidases and esterases, two classes of enzymes capable of attacking lignite, were increased in the cell-free filtrate of the culture. (C) 2006 Elsevier Ltd. All rights reserved.