%0 Journal Article
%T Hexavalent Chromate Reductase Activity in Cell Free Extracts of Penicillium sp.
%A Damaris L. Ar¨¦valo-Rangel
%A Juan F. C¨¢rdenas-Gonz¨¢lez
%A V¨ªctor M. Mart¨ªnez-Ju¨¢rez
%A Ismael Acosta-Rodr¨ªguez
%J Bioinorganic Chemistry and Applications
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/909412
%X A chromium-resistant fungus isolated from contaminated air with industrial vapors can be used for reducing toxic Cr(VI) to Cr(III). This study analyzes in vitro reduction of hexavalent chromium using cell free extract(s) of the fungus that was characterized based on optimal temperature, pH, use of electron donors, metal ions and initial Cr(VI) concentration in the reaction mixture. This showed the highest activity at 37¡ãC and pH 7.0; there is an increase in Cr(VI) reductase activity with addition of NADH as an electron donor, and it was highly inhibited by Hg2+, Ca2+ and Mg2+, and azide, EDTA, and KCN. 1. Introduction Chromium (Cr) toxicity is one of the major causes of environmental pollution emanating from tannery effluents. This metal is used in the tanning of hides and leather, the manufacture of stainless steel, electroplating, and textile dyeing and used as a biocide in the cooling waters of nuclear power plants, resulting in chromium discharges causing environmental concerns [1]. Cr exists in nine valence states ranging from £¿2 to +6. Of these states, only hexavalent chromium [Cr(VI)] and trivalent chromium [Cr(III)] have primary environmental significance because they are the most stable oxidation forms in the environment [2]. Both are found in various bodies of water and wastewaters [3]. Cr(VI) typically exists in one of these two forms: chromate ( ) or dichromate ( ), depending on the pH of the solution [3]. These two divalent oxyanions are very water soluble and poorly adsorbed by soil and organic matter, making them mobile in soil and groundwater [2]. Both chromate anions represent acute and chronic risks to animals and human health since they are extremely toxic, mutagenic, carcinogenic, and teratogenic [4]. In contrast to Cr(VI) forms, the Cr(III) species, predominantly hydroxides, oxides, or sulphates, are less water soluble, mobile (100 times less toxic) [5], and (1,000 times less) mutagenic [6]. The principal techniques for recovering or removing Cr(VI), from wastewater are chemical reduction and precipitation, adsorption on activated carbon, ion exchange, and reverse osmosis, in a basic medium [7]. However, these methods have certain drawbacks, namely, high cost, low efficiency, and generation of toxic sludge or other wastes that require disposal and imply operational complexity [8]. An alternative to these methods is the removal of heavy metal contaminants by microorganisms. The metal removal ability of microorganisms, including bacteria [2, 6, 8, 9], microalgae [7, 10], and fungi [1, 11], has been studied extensively. Fungi, in
%U http://www.hindawi.com/journals/bca/2013/909412/