Fast and efficient cadmium biosorption by Chlorella vulgaris K-01 strain: The role of cell walls in metal sequestration

In this study a newly identified algal strain, isolated from a saline synanthropic environment and identified as Chlorella vulgaris has been investigated in terms of its physiological responses to elevated cadmium concentrations. Furthermore, cadmium binding capacity and mechanisms that underlie of the cadmium biosorption by these Chlorella vulgaris K-01 cells are described. The mechanism of ion binding is based on chemisorption with a high initial sorption rate. The capacity of Cd2+ removal by living biomass of Chlorella vulgaris K-01 was found to be independent of initial pH over a broad pH range (6.0–9.0). The subsequent FTIR and XPS analyses demonstrated a crucial role of cell wall components containing amino and carboxyl residues in the sorption of cadmium ions. Chlorella vulgaris K-01 can withstand Cd2+ concentrations up to 44.5 μM without significant oxidative stress symptoms and without photosynthesis inhibition impairing its proliferative activity. Chlorella vulgaris K-01 also tolerated an elevated salinity up to 4% NaCl. We conclude that Chlorella vulgaris K-01 possesses substantial potential in cadmium adsorption, suitable for industrial scale applications.