The biosolubilisation of coal is a promising coal processing technology for converting solid coal to liquid oil at ambient conditions. In this study, the biosolubilisation of Chinese lignite was studied using a fungus isolated from decaying wood. The intensity of biosolubilisation was determined by estimating the liquid formation time and by measuring the weight loss of the lignite granules gravimetrically. The biosolubilisation product (black liquid) was characterized by ultraviolet spectroscopy, infrared spectroscopy, gas chromatography-mass spectrometry, element analysis, and heating value. Results showed that this fungus isolated from the decaying wood solubilised 31.83% (by weight) of Chinese lignite to black liquid within 11 days at 27.5 degrees C. The biosolubilisation product mainly contained aromatic acids and chain hydrocarbons, and had organic function groups of hydroxyl, cyclane, carbonyl, ether linkage and aromatic rings. The heating value of the biosolubilisation product was 14 MJ/kg. Chemical analysis of the biosolubilisation product indicated that side chains of lignite were important structures in the biosolubilisation mechanism. (C)) 2009 Elsevier Ltd. All rights reserved.