Streptomyces sp. MC1 as strategy of Cr(VI)-contaminated environment remediation

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

Contaminated Soils: Environmental Impact, Disposal and Treatment

Nova Science Publishers, Inc

Lugar: Nueva York; Año: 2009;

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. 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. Their metabolic diversity and the particular growth characteristics indicate them as agents for bioremediation. A Cr(VI) resistant actinomycete strain, Streptomyces sp. MC1, has the ability of reducing Cr(VI) present in a synthetic medium, soil extract and soil sample. Also, Streptomyces sp. MC1 has shown ability to accumulate Cr(III). Chromate reductase activity of Streptomyces sp. MC1 is an enzyme associated principally to the biomass, it is constitutive and requires an electron donor (NAD(P)H). It is active over a wide range of pH (5-8) and temperature (19-39 ºC), being its optimum conditions 30 ºC and pH 7. Once Cr(VI) is reduced to Cr(III), it is accumulated by Streptomyces sp. MC1. Cytochemical staining shows Cr(III) deposits as black grains within the cell exposed; whereas cells cultivated in a chromium-free medium do not show clear deposits, revealed by transmission electron microscopy. Because the chromate reductase of Streptomyces sp. MC1 is present in supernatant, pellet and cell free extract, it could be utilized in processes of bioremediation in systems non-compatible with the cell reproduction, frequent conditions in environments contaminated. Streptomyces sp. MC1 or its compounds could be used for Cr(VI) reduction and removal in biotechnological processes applied to environmental samples.