BIOREMEDIATION OF CHROMIUM CONTAMINATED SOILS BY ACTINOMYCETES: MECHANISMS ENVOLVED

POLTI, MARTA ALEJANDRA; AMOROSO, MARÍA JULIA; ABATE; CARLOS MAURICIO

Bioremediation: Biotechnology, Engineering and Environmental Management

Nova Publisher

Lugar: Nueva York; Año: 2011; p. 423 - 434

In natural water and subsurface soils chromium occurs in two major oxidation states: III and VI. Cr(VI) is approximately 1,000-fold more cytotoxic and mutagenic than Cr(III). As the application of Cr is extensive in several industries, chromium-associated pollution is an increasing problem. Development of suitable methods for cleaning up such contaminated soils is an important topic of environmental recovery and protection, particularly regarding methods for remediation of Cr(VI)-contaminated soils. At present there exist physicochemical technologies to remove Cr(VI) from industrial waste, but these methods are costly and require much energy and specific equipment. Therefore the employment of lower-cost biotechnology could be an important alternative.   The three processes, by which the microorganisms interact with Cr(VI), are biosorption, bioaccumulation and enzymatic. Biosorption is a metabolism-independent process and thus can be performed by both living and dead microorganisms. Bioaccumulation involves metabolism dependent active uptake of metals. Biological transformation of Cr(VI) to Cr(III) by enzymatic reduction is a means of chromium decontamination. This biological reduction may provide a less costly and environmentally friendly approach to remediation. Actinomycetes are the dominant population in soil. Metal-resistant actinobacteria, and their potential use for bioremediation strategies, have been described.   Recent progress has been made studying metal resistance in streptomycetes isolated from polluted areas. The general strategy for control of Cr (and other heavy metal) pollution has relied upon dissimilatory metal reduction, that is the uptake of toxic and permeable Cr(VI) molecules by microorganisms and plants and their subsequent bioremediation and conversion into less toxic trivalent. In particular, the mechanism of Cr(VI) resistance observed in Streptomyces sp. MC1, a strain able to remove bioavalible Cr(VI) from soil, includes adsorption coupled with reduction to Cr(III), and finally, Cr(III) bioaccumulation. This mechanism have special relevance to remediation of Cr(VI) contaminated environments.