Enhanced lipid accumulation of green microalga Scenedesmus sp. by metal ions and EDTA addition

Effects of Fe3+ (0–0.12 g/L), Mg2+ (0–0.73 g/L) and Ca2+ (0–0.98 g/L) on the biomass and lipid accumulation of heterotrophic microalgae were investigated in dark environment. The biomass and lipid production exhibited an increasing trend with increasing the concentrations of metal ions. In cultures with 1.2 × 10−3 g/L Fe3+, 7.3 × 10−3 g/L Mg2+ and 9.8 × 10−4 g/L Ca2+, the maximum biomass, total lipid content and lipid productivity reached 3.49 g/L, 47.4% and 275.7 mg/L/d, respectively. More importantly, EDTA addition (1.0 × 10−3 g/L) could enhance the solubility of metal ions (iron and calcium) and increase their availability by microalgae, which evidently promote the lipid accumulation. Compared with the control, the total lipid content and lipid productivity increased 28.2% and 29.7%, respectively. These show that appropriate concentrations of metal ions and EDTA in the culture medium were beneficial to lipid accumulation of heterotrophic Scenedesmus sp. cells.