Microalgae cultivation and industrial waste: New biotechnologies for obtaining silver nanoparticles

Industrial effluents containing heavy metals can have harmful effects on organisms and the ecosystem. Silver is a waste from textile, galvanic and photographic industries, and when released into the environment, it can harm human health and cause biological modification. Removal of metals, such as silver, has been traditionally carried out using physicochemical methods that produce a high concentration of sludge and expend a significant amount of energy. Researchers are seeking innovative technologies for more efficient removal of silver or for using this heavy metal to obtain new products. The use of microalgae is a promising alternative to traditional remediation methods because several species can absorb and assimilate heavy metals. When exposed to toxic substances, microalgae excrete molecules in the medium that induce the reduction of silver particles to nanoparticles. Biosynthesized silver nanoparticles (AgNPs) can be used in medicine, food packaging, the production of cosmetics and pharmaceuticals, civil engineering, sensors and water purification. Thus, microalgal biosynthesis of metal nanoparticles has the capacity to bioremediate metals and subsequently convert them into non-toxic forms in the cell. In this context, this review addresses the use of microalgal biotechnology for industrial waste remediation of silver, which includes the simultaneous biosynthesis of AgNPs. We also discuss the potential applications of these nanoparticles.