Effective Factors and Molecular Mechanisms of Heavy Metal Bioremediation Using Cyanobacteria

The sustainability and non-biodegradability of heavy metals, on the one hand, and the increasing environmental pollution caused by industrial wastewater on the other hand have increased the attention to heavy metal remediation. Cyanobacteria are one of the most important agents of heavy metals removal in drought and aquatic environments. Their ability to remove metals is related to various mechanisms such as their high surface-to-volume ratio, the presence of functional groups with high affinity for binding to metals at their cell wall and exopolysaccharides, and efficient metal absorption and storage systems such as metallothioneins, the presence of enzymatic antioxidants (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) as well as non- enzymatic antioxidants (carotenoids, ascorbic acid, glutathione, and flavonoids). Various factors such as heavy metal concentration, pH, temperature, biomass concentration, and different ions could be effective on heavy metal bioremediation using cyanobacteria. This review article discusses the benefits of using cyanobacteria in heavy metal bioremediation and their molecular mechanisms of resistance to heavy metals.