The potential of microalgae in phycoremediation

Abstract

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) can have negative impacts on the marine and freshwater biota. Utilizing microbes, particularly microalgae, which are able to extract metals and hydrocarbons from environmental matrices, the impact of these contaminants in freshwaters, seas, and wastewaters can be reduced. In fact, the contaminants can be passively absorbed and actively accumulated within the organelles of microalgae, reducing their negative impact. River streams, untreated municipal, agricultural, and industrial wastewaters, represent one of the most important issues for the anthropogenic pollution. Microalgae and bacteria can grow in polluted waters containing different metals as cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), copper (Cu), and mercury (Hg). They are able to accumulate metal elements within biomass in a dose-dependent manner and are employed in bioremediation thanks to their growth ability in polluted sites. In the following chapter, we analyze the potential of employing microalgae in phycoremediation, their mechanisms of tolerance and resistance to heavy metals, the possibility to use consortia of microorganisms instead of single specie to cope with complex polluted matrices, the possibility to metabolic engineer microalgae to gain their function, and the employment of microalgae in both liquid and solid devices.