Microalgal bioremediation of heavy metals and by-products recovery as lipid: the dual role of microalgae

The heavy metals like arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg) are extremely toxic to the environment and human health. Modern techniques have recently increased the focus on heavy metal remediation in contaminated water. Bioremediation provides an ideal environment to the ecosystem ensuring safe, simple and sustainable technology, as it relies on microorganisms to remove contaminants from contaminated and wastewater. Although heavy metal bioremediation is cost-effective method, but efforts to develop integrated remediation systems aim to make the process more affordable and sustainable. In this context, microalgae are increasingly used in heavy metal remediation due to its wide availability, low cost, and high removal efficiency. Keeping this view in mind, this review disseminates information about various microalgae used for removal of heavy metals and their mechanisms of action including extracellular and intracellular mechanisms. Additionally, this also focuses on the by-product recovery with special reference to lipid accumulation. Moreover, this review also elaborates on recent research in the use of microalgae in the biosorption and bioremediation of heavy metals and provides a baseline information. Further study shall need to develop new technologies by using microalgae that meet environmental clean and production of lipid, which may be a promising source for the production of biofuel and biodiesel.