Mechanism of bacterial reduction and biosorption of hexavalent chromium

Abstract:

Hexavalent chromium [Cr(Ⅵ)] is a carcinogen with the toxicity far greater than that of trivalent chromium. The Cr(Ⅵ) discharged by electroplating and tanning have adverse effects on human health and eco-environment. The Cr(Ⅵ) resistance mechanism and reduction process of Cr(Ⅵ)-reducing bacteria have been discussed, whereas there is a lack of summary of the species, chromate reductase activity, and adsorption mechanism of Cr(Ⅵ)-reducing bacteria. In this review, we reviewed the recently reported Cr(Ⅵ)-reducing bacteria via a phylogenetic tree, elaborated the mechanism of Cr(Ⅵ) reduction by bacteria, summarized the enzymatic parameters and reaction conditions of chromate reductase, and expounded the environmental factors affecting the reduction of Cr(Ⅵ) by bacteria. Further, we clarified the adsorption performance and mechanism of Cr(Ⅵ) by bacteria. Finally, we put forward the research prospects on the mechanism of bacterial bioremediation of Cr(Ⅵ) contamination. With this review, we aim to deepen the understanding about the reduction and biosorption processes of Cr(Ⅵ)-reducing bacteria.