Bacterial reduction of hexavalent chromium

Abstract

Cr(VI)-reducing bacteria are widespread and Cr(VI) reduction occurs under both aerobic and anaerobic conditions. Under aerobic conditions, both NADH and endogenous cell reserves may serve as the electron donor for Cr(VI) reduction. Under anaerobic conditions, electron transport systems containing cytochromes appear to be involved in Cr(VI) reduction. High cell densities are necessary to obtain a significant rate of Cr(VI) reduction. Cr(VI) reduction by bacteria may be inhibited by Cr(VI), oxygen, heavy metals, and phenolic compounds. The optimum pH and temperature observed for Cr(VI) reduction generally coincide with the optimal growth conditions of cells. The optimum redox potential for Cr(VI) reduction has not yet been established.

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

“…Such microorganisms, known as dissimilatory metal-reducing bacteria, are phylogenetically (Lonergan et al, 1996) and physiologically (Lovley et al, 1997) diverse; although, most share the ability to use Fe 3+ and S 0 as terminal electron acceptors (Lovley et al, 1997). The microbial reduction of Cr 6+ to Cr 3+ has been one of the most widely studied forms of metal bioremediation (Lovley, 1995;Wang and Shen, 1995). A wide diversity of heterotrophic organisms are known to carry out this reaction which, depending upon the organism, can take place anaerobically or aerobically (Wang and Shen, 1995;Lovley, 1993).…”

“…The microbial reduction of Cr 6+ to Cr 3+ has been one of the most widely studied forms of metal bioremediation (Lovley, 1995;Wang and Shen, 1995). A wide diversity of heterotrophic organisms are known to carry out this reaction which, depending upon the organism, can take place anaerobically or aerobically (Wang and Shen, 1995;Lovley, 1993).…”

Redução química e biológica do cromo hexavalente aplicado ao solo

“…Deste modo, neste tratamento, a avaliação da atividade biológica na redução foi dificultada. A redução microbiana do Cr 6+ tem sido estudada com vistas em ampliar as alternativas para a remediação de áreas contaminadas com esta forma de cromo (De Leo & Ehrlich, 1994;Wang & Shen, 1995). Losi et al (1994a) …”

Metallophilic fungi research: an alternative for its use in the bioremediation of hexavalent chromium

“…The microbial reduction of Cr(VI) to Cr(III) by fungi, yeast and bacteria has been one of the most studied mechanisms for the bioremediation of this metal (Lovley 1995;Wang and Shen 1995;Lonergan et al 1996). In this way, the strategy for Cr(VI) bioremediation is to reduce it to Cr(III) not only to decrease the Cr(VI) toxicity but also to immobilise the insoluble form of Cr(III) as Cr(OH) 3 in soil at pH values of 6-9 (Sharma and Forster 1993;Tokunaga et al 1999;Pellerin and Booker 2000).…”