A green microalgae strain, Chlorococcum sp. was obtained from tropical freshwater in Indonesia. The effects of pH on growth, effects of salt, carbon dioxide level, nitrate, acetate, and photoperiod on biomass and lipid production were studied. The fatty acids composition was also investigated. This study shows that the strain had an optimum pH value for growth ranging from pH 8.0 to 8.5. The biomass concentration and lipid content were influenced by different concentrations of salt, CO2 and nitrate. The lipid productivity ranged from 2 to 90.8 mg L-1 d(-1) in different mediums. The highest biomass concentration and total lipid content achieved were 1.75 g L-1 and 56% of dry weight, respectively. Moreover, the major fatty acid methyl esters were C16:0, C18:1, C18:2 and C18:3. The high lipid content and the fatty acid composition make the strain Chlorococcum sp. a potential resource for food, cosmetics and biodiesel. (C) 2012 Elsevier Ltd. All rights reserved.