Nickel Adsorption by Wild type and Nickel Resistant Isolate of Chlorella sp.

Use of unicellular green microalgae has several advantages over conventional methods for removing heavy metals from contaminated sites. Here, a comparative study was made to investigate nickel detoxification mechanisms between a wildtype (WT) Chlorella sp. and a nickel resistant, EMS-5 cell line isolated from the same species by EMS (Ethyl Methane Sulphonate) mutagenesis. Results showed that the growth rate of the tested algal cells was inhibited with increasing nickel concentrations in the liquid growth medium. Higher ID50 value of EMS-5 compared to the WT revealed some degree of resistance to nickel. Removal and adsorption of Ni2+ were found rapid during the first few hours in both the algal cultures when exposed to 50 M Ni2+. However, kinetic experiments showed significantly higher removal and adsorption of Ni2+ by EMS-5 compared to the WT throughout the treatment hours. Besides, the total nickel accumulation, surface bound and intracellular nickel in EMS-5 was significantly higher to that of the WT. Hence, the EMS-5 appeared more resistant to nickel.