Removal of copper improves the lipid content in Nannochloropsis oculata culture

Mining is an important activity for the economic development of many countries. However, this activity produces toxic residues that pollute water and the environment. The heavy metal removal from effluents of acid mine water is crucial to avoid environmental pollution. The microalga Nannochloropsis oculata was cultured in algal medium, with the addition of 1.16, 1.74, 2.32, 3.48, and 4.64 mg Cu²⁺ L^-1 coming from acid mine water to assess its removal capacity and the effect of copper content on the cell density and lipid productivity. The results showed that N. oculata removed up to 94.88 ± 0.43% at copper concentration than 1.74 mg Cu²⁺ L^-1; additionally, a positive effect on the lipid content was found at copper concentration to be higher, 4.64 mg Cu²⁺ L^-1, yielding 77.04 ± 2.60% of lipid content, twice as high as that achieved in the control culture of 33.058 ± 5.398%, thus potentiating the biodiesel production. These findings are favorable because they indicate that microalgae can remove copper added in the culture and present in acid mine water and can yield high lipid content at the same time. The cell density and growth rate decreased with increased concentrations of copper in the culture medium.