Optimal growth conditions and heavy metal removal of Coelastrella sp. CORE-3 isolated from wastewater

Abstract

This study was investigated to optimize growth conditions of native microalgae (Coelastrella sp. CORE-3) from wastewater, evaluate the removal of Cu²⁺, Zn²⁺, Cd²⁺ and Ni²⁺ and compare both isolated microalgae and Ankistrodesmus bibraianus, and describe their sorption mechanisms on the cell surface. The effects of the pH, light: dark cycle and temperature on the growth of the isolated Coelastrella sp. CORE-3 was optimized. The optimal L:D cycle, temperature, and pH conditions were 14:10 hr, 25℃, pH 7. The growth of isolated microalgae, Coelastrella sp. CORE-3. was compared with A. bibraianus. The removal efficiency of heavy metals by Coelastrella sp. CORE-3 and A. bibraianus were found as follows, respectively: (live cell) Zn²⁺ > Cd²⁺ > Cu²⁺ > Ni²⁺, (dead cell) Cu²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺. SEM analysis indicated that more cell surface deformation occurred in A. bibraianus compared to Coelastrella sp. after exposure to heavy metals. This result suggests that Coelastrella sp. CORE-3 has more resistant to heavy metal toxicity. In addition, based on the FT-IR analysis, the live cells of Coelastrella sp. CORE-3 and A. bibraianus showed the interactions of heavy metals with the functional groups: alcohol, alkane, amide, amine on their cell surfaces.