Removal Efficiency of Cr6+by IndigenousPichiasp. Isolated from Textile Factory Effluent

Pablo M Fernández,Julia I Fariña,Lucia I C Figueroa,María M Martorell

doi:10.1100/2012/708213

Abstract

Resistance of the indigenous strains P. jadinii M9 and P. anomala M10, to high Cr6+ concentrations and their ability to reduce chromium in culture medium was studied. The isolates were able to tolerate chromium concentrations up to 104 μg mL−1. Growth and reduction of Cr6+ were dependent on incubation temperature, agitation, Cr6+ concentration, and pH. Thus, in both studied strains the chromium removal was increased at 30°C with agitation. The optimum pH was different, with values of pH 3.0 and pH 7.0 in the case of P. anomala M10 and pH 7.0 using P. jadinii M9. Chromate reduction occurred both in intact cells (grown in culture medium) as well as in cell-free extracts. Chromate reductase activity could be related to cytosolic or membrane-associated proteins. The presence of a chromate reductase activity points out a possible role of an enzyme in Cr6+ reduction.

Highlights

Heavy metals found in wastewaters are harmful to the environment and their effects on biological systems are very severe
Chromium exists in several oxidation states from Cr2+ to Cr6+
Cr6+ resistance of P. jadinii M9 and P. anomala M10 was evaluated by growth response of the strains under different concentrations of Cr6+

Summary

Introduction

Heavy metals found in wastewaters are harmful to the environment and their effects on biological systems are very severe. Trivalent and hexavalent forms are the dominant oxidation states. The toxicity of chromium is dependent on its oxidation state, Cr3+ is rather benign and adsorbed in soils and waters; whereas Cr6+, which is the toxic form, is not readily adsorbed and is soluble [2]. Cr6+, a carcinogenic element, is highly toxic to all forms of life but Cr3+, an essential micronutrient for many higher organisms, is relatively insoluble in water and 100 times less toxic than Cr6+ [3]. Chromium hexavalent toxicity is believed to be caused by the negatively charged chromate oxyanion, which can be transported into microbial cells. The oxyanion is believed to undergo immediate reduction reactions leading to the formation of various reactive intermediates, which are harmful to the cell organelles, proteins, and nucleic acids [4]

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Conclusion