Microbial lipid accumulation to provide alternative oil resources is an exciting research area, obtaining increasing attentions recently for the biodiesel production due to its high production efficiency and less demand of agricultural land. The aim of this study is to optimize the lipid accumulation of Chlorella vulgaris by using various carbon sources in heterotrophic and mbcotrophic cultures. Different cultivation factors were studied on their influences to the cell growth and oil accumulation. Our results revealed that C. vulgaris could grow on autotrophic, mixotrophic and heterotrophic modes; and the mixotrophic cultivation especially could produce more cell biomass than the autotrophic or heterotrophic cultures individually or combined. The substrate concentration significantly influenced the final cell yield of the mixotrophic cultivations while the cell lipid content remained relatively constant. Glycerol was inhibitive to the cell growth while the microalgae strain could actively utilize acetate as the carbon source. This provides a promising niche in reducing the overall cost of biofuel production since this substrate can be obtained from some waste processes such as anaerobic digestion. (C) 2011 Elsevier Ltd. All rights reserved.