Effects of different nitrogen and phosphorus concentrations on the growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp.

Microalgae have high potential to remove inorganic nutrients from wastewater and to produce biodiesel. Effects of nitrogen and phosphorus concentrations on growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp. LX1 were studied. Scenedesmus sp. LX1's growth was in accordance with the Monod model. The following Monod parameters were obtained: the N- and P-saturated maximum growth rate was 2.21 x 10(6) cells m L(-1)d(-1), and the half-saturation constants of N and P uptake were 12.1 mg L(-1) and 0.27 mg L(-1), respectively. In the nitrogen/phosphorus ratio of 5:1-12:1, 83-99% nitrogen and 99% phosphorus could be removed. In conditions of nitrogen (2.5 mg L(-1)) or phosphorus (0.1 mg L(-1)) limitation, Scenedesmus sp. LX1 could accumulate lipids to as high as 30% and 53%, respectively, of its algal biomass. The lipid productivity/unit volume of culture, however, was not enhanced. Further research should be made on how to enhance both lipid content and lipid productivity.