Microbial oil is drawing increasing interest all over the world as an alternative non-food feedstock for biodiesel production. Rhodosporidium toruloides has been considered as a promising candidate to convert glycerol into microbial oils due to its good substrate adaptability, high intracellular lipid content, and the potential of co-production of some pigments. Interestingly, we have also found that sodium lignosulphonate (SL) could significantly enhance the cell growth and lipid accumulation of R. toruloides. In the present work, we investigated the possible mechanisms for the enhancement of lipid production by SL. It was found that SL could not be utilized by R. toruloides as a carbon source. No apparent changes on the morphology of cell membranes and the fatty acid profiles of microbial lipids were found when SL was added. Further experiments indicated that the volumetric oxygen transfer coefficient was increased by nearly 15% on average by adding 4 g/L SL, which might be the main mechanism for the improvement of lipid production. (C) 2015 Elsevier Ltd. All rights reserved.