Phycoremediation of Copper by Chlorella protothecoides (UTEX 256): Proteomics of Protein Biosynthesis and Stress Response

Abstract

Phycoremediation is an eco-friendly treatment for mining wastes. Copper at high concentrations is toxic for microalgae growth (bioremediation). Proteomics is a modern approach that can assist in elucidating, in detail, the highly complex metabolic mechanisms related to phycoremediation. Therefore, this study aimed to evaluate the effect of copper ions (Cu2+) on the metabolism of Chlorella protothecoides (UTEX 256), particularly the proteome changes. The WC culture medium supplemented with Cu2+ at 0.3, 0.6, and 0.9 mg/L showed a strict correlation to Cu2+ removal of 40, 33, and 36% of the initial content, respectively. In addition, Cu2+ concentrations did not affect microalgae growth—a very traditional approach to measuring toxicity. However, the proteomics data indicated that when compared to the control, reductions in protein levels were observed, and the 10 most scored proteins were related to the light-harvesting complex. Interestingly, C. protothecoides cultivated at 0.9 mg of Cu2+/L biosynthesized the protein Ycf3-interacting chloroplastic isoform X1 to respond to the photooxidative stress and the DNA-directed RNA polymerase III subunit RPC5 was related to the Cu2+ binding. Pre-mRNA-processing factor 19 and cytochrome c peroxidase proteins were observed only in the copper-containing treatments indicating the activation of antioxidant mechanisms by reactive oxygen species, which are potential environmental pollutant biomarkers.