Superintending Scenedesmus and Chlorella sp. with lead and cobalt tolerance governed via stress biomarkers

Abstract

In this study, Scenedesmus sp. and Chlorella sp. were exposed to 100, 150, 200 mg/L of lead and 10, 50, 100 mg/L of cobalt for 10 days. The chlorophyll content at Pb (200 mg/L) was found to be 2.35 ± 0.15 μg/mL in Scenedesmus sp. and 2.58 ± 0.02 μg/mL in Chlorella sp. on the 10th day. Scenedesmus sp. and Chlorella sp. exposed to Co (100 mg/L) showed a decline in chlorophyll content (0.83 ± 0.09 μg/mL and 0.74 ± 0.08 μg/mL) respectively. Furthermore, Scenedesmus sp. and Chlorella sp. exposed to 100 mg/L of lead showed the highest lipid peroxidation measured using malonaldehyde (MDA) (10.60 μmol/g and 6.24 μmol/g), superoxide dismutase (SOD) (49.04 U/mL and 49.32 U/mL) and catalase (CAT) (237.74 nmol/min/mL and 373.48 nmol/min/mL) activity, respectively. Scenedesmus sp. and Chlorella sp. exposed to 200 mg/L of lead showed elevated MDA (4.89 μmol/g and 5.14 μmol/g), SOD (32.05 U/mL and 37.80 U/mL) and CAT (121.78 nmol/min/mL and 160.46 nmol/min/mL) activity, respectively. Scenedesmus sp. and Chlorella sp. showed a high tolerance for 100 mg/L of lead and 10 mg/L of cobalt. As the concentration of lead and cobalt was increased, cell growth declined and elevated levels of stress biomarkers were observed. This study helps to understand plant tolerance levels and presents their candidature for treating wastewater with high lead and cobalt content. HIGHLIGHTS Scenedesmus sp. and Chlorella sp. were explored for expression of stress biomarkers when exposed to various concentrations of Pb and Co.; Chlorophyll content at higher concentrations of Pb and Co declined in both species.; SOD and catalase activity were upregulated at higher concentrations of Pb and Co in both species.; MDA, SOD and catalase were identified as physio-chemical bioindicators.;

Keywords

• antioxidant enzymes
• biomarkers
• bioremediation
• heavy metals
• microalgae
• ros