Growth response and lipid content of Chlorella vulgaris under different nominal Mg²⁺ additions

Abstract

The depletion of fossil fuels as the primary energy source has increased concerns about a global energy crisis, making renewable energy development through microalgae increasingly important. Chlorella vulgaris is a promising microalga due to its high biomass productivity and lipid-accumulation capacity. This study evaluated the growth and lipid responses of Chlorella vulgaris to nominal Mg²⁺ additions of 0, 0.4, 0.8, 1.2, and 1.6 ppm, supplied as MgSO₄·7H₂O, during 7 days of cultivation in sterile seawater. Cell density, dry biomass, and gravimetric crude lipid were evaluated. Each treatment consisted of one culture unit without independent replication; therefore, data were analysed descriptively. The highest cell density was observed at 1.6 ppm on day 7 (27,923.13 × 10⁴ cells/mL), dry biomass was highest at 0.4 ppm (1.52 g/L), and crude lipid was highest at 0.8 ppm (65.94%). At 0.8 ppm, lipid concentration and productivity were approximately 0.87 g/L and 0.124 g/L/day. The tested nominal Mg²⁺ additions were associated with distinct numerical response patterns in Chlorella vulgaris, with the highest cell density at 1.6 ppm, the highest dry biomass at 0.4 ppm, and the highest lipid content at 0.8 ppm.