The green microalga strain, Botryococcus braunii KMITL 2, was isolated from a freshwater reservoir in central Thailand, and the effects of light, nitrogen, phosphorus, iron, cultivation time and salinity on lipid production were studied by varying parameters one at a time. When cultured in Chlorella medium containing 222 mg L-1 phosphorus (PO43- P) under continuous illumination of 200 mu E m(-2) s(-1) with a salinity of 0 psu, a maximum lipid content of 54.69 +/- 3.13% was obtained. Its high lipid content makes strain KMITL 2 a potential source for biodiesel production in tropical regions. (C) 2011 Elsevier Ltd. All rights reserved.