Phycoremediation of Heavy Metals by Chlorella pyrenoidosa and Spirogyra communis

Environmental contamination by heavy metals is a serious problem due to their incremental accumulation in the food chain. Unlike most organic wastes and the microbial load in aquatic bodies, metal contaminants are not biodegradable, tending to accumulate in living organisms, thus becoming a permanent burden on ecosystems (Bayo, 2012). Most heavy metals are transition elements with incompletely filled d-orbitals. These dorbitals provide heavy metal cations with the ability to form complex compounds. Trace amounts (μg L -1 ) of some metal ions such as copper, zinc, cobalt, iron, nickel are required by living organisms as cofactors for the enzymatic activities. However, heavy metal ion concentrations at ppm (mg L -1 ) level are known to be toxic to the organisms because of irreversible inhibition of many enzymes by the heavy metal ions. The process of accumulation and adsorption of metals by algae involves adsorption onto the cell surface (wall, membrane or external polysaccharides) and binding to cytoplasmic ligands, phytochelatins and metallothioneins, and other intracellular molecules. The algal cell wall has many International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 5 Number 10 (2016) pp. 920-930 Journal homepage: http://www.ijcmas.com