Metal adsorption and nanoparticles formation by microorganisms

Recovery of valuable metals from industrial effluents and environmental remediation are currently performed by using biomaterials. Removal of metals from solutions using biomasses offers advantages over physicochemical methods, especially when they are found at low concentrations. Biosorption can be defined as the removal of metal or metalloid species, compounds, and particulates from solution by biological material. Metals can be accumulated in biomass by a variety of processes dependent and independent from metabolism. Both living and dead biomass, as well as cellular products, can be used for metal removal. Bacterial biomass has shown important potential for bioadsorption. Microorganisms are being studied in order to produce metallic nanoparticles that can have potential applications in advanced materials used in electronics, pharmaceutics, and energy. Nanoparticles are substances smaller than 100 nm in dimension, that possess more than one dimension and its physicochemical properties are different from those presented by material in the size range of centimeters. They can be spherical, tubular, or irregularly shaped and can be given in the form of alloys, aggregates, or agglomerates. According to their origin, nanoparticles can be divided into natural and anthropogenic. In this chapter, an overview of metal sorption and metal nanoparticles formation by microorganisms is given. In addition, part of the research being performed at the Professional Interdisciplinary Unit of Biotechnology, National Polytechnical Institute (IPN) is presented. Research focused essentially on the isolation of microorganisms resistant to metals, and to study the ability of these microorganisms to accumulate metals and form metal nanoparticles.