High ammonia tolerance on growth rate of marine microalga Chlorella vulgaris

Abstract

Aim: In order to evaluate the effects of ammonia on microalgae growth, Chlorella vulgaris was cultivated in ammonium nitrogen. Methodology: The marine microalgae, Chlorella vulgaris was cultivated in algal media containing increasing concentrations of ammonium concentrations at 320, 640, 960, 1600 mg l-1, with free ammonia concentrations of 0.64 to 2.97 mM and pH ranging from 7.78 to 7.82. An addition ammonia treatment was 1600mgl-1 that hadafree ammonia concentrationof 13.30 mM, whileacontrol was NaNO3 at 100 mgl-1. Results: C. vulgaris grew faster when cultured using ammonium nitrogen than nitrate nitrogen. The dry weight of C. vulgaris increased even under extremely high ammonium conditions of 1600 mg-N l-1, which initially contained 2.97 mM free ammonia and reached around 4 g-ds l-11. Algal growth was inhibited in the beginning of the experiment at the highest initial free ammonia concentration of 13.30 mM. However, the cell density increased 2days later when free ammonia concentration decreasedto 3.7 mM duetodecrease inpHfrom 8.48to7.88, and the maximum area productivityof 21.12 g-ds m-2 d-1 was observed. Interpretation: These results showed that C. vulgaris could maintain high productivity even in high free ammonia concentrations of 3.7 mM. Because of the high tolerance for free ammonia compared with other microalgae, C. vulgaris can be used for the aquaculture industry by removing ammonia from wastewater, and thus improving the water quality.