Author(s): Camargo FA, Okeke BC, Bento FM, Frankenberger WT
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Abstract Chromium-resistant bacteria (CRB) isolated from soils can be used to reduce toxic Cr(VI) from contaminated environments. This study assessed in vitro reduction of hexavalent Cr using a cell-free extract (CFE) of CRB isolated from soil contaminated with dichromate. One isolate, ES 29, that substantially reduced Cr(VI) was identified as a Bacillus species by 16S rRNA gene-sequence homology. The isolate reduced Cr(VI) under aerobic conditions, using NADH as an electron donor and produced a soluble Cr(VI)-reducing enzyme stimulated by copper (Cu2+). The CFE of the bacterial isolate reduced 50\% of Cr(VI) in 6 h. The Cr(VI)-reduction activity of the CFE had a Km of 7.09 microM and a Vmax of 0.171 micromol min(-1) mg(-1) protein. Mercury inhibited the enzyme, but not competitively, with a Vmax of 0.143 micromol min(-1) mg(-1) protein, a Km of 7.07 microM and a Ki of 1.58 microM. This study characterizes the enzymatic reduction of Cr(VI) by Bacillus sp. ES 29 which can be used for the bioremediation of chromate.
This article was published in Appl Microbiol Biotechnol
and referenced in Journal of Petroleum & Environmental Biotechnology