Effect of magnesium ion concentration in autotrophic cultures of Chlorella vulgaris

Chlorella vulgaris was grown autotrophically in shake-flask cultures in the presence of different initial Mg2 + ions concentrations in the range of 8.9-465.0 mg/L. No inhibition of growth was observed even at the highest concentration of magnesium tested. An existing extraction method was modified and applied to the cultures in order to measure the Mg2 + ions associated with the biomass. A distinction was made between the Mg2 + ions adsorbed onto the cells and the absorbed Mg2 + ions which were more strongly associated with the biomass. The cells became saturated with absorbed ions at approximately 46.1 mg Mg2 +/g DW biomass but the amount of adsorbed Mg2 + ions associated with the biomass increased in proportion with the initial concentration of these ions in the medium. The authors propose that the saturation level of the adsorbed Mg2 + ions was not reached in these experiments even at the highest concentration tested. The experimental data of all Mg2 + ions concentrations tested fitted well with an exponential model for the metal removal from the medium.