Hexavalent chromium removal by a resistant strain Bacillus cereus ZY-2009

Bioreduction of Cr(VI) to Cr(III) by reducing microbes has attracted increasing concern. Here, Cr(VI) removal capacity of a Cr(VI)-resistant bacterium isolated from activated sludge was investigated. Based on its physio-biochemical attributes and 16S rDNA sequence analysis, the strain was identified as Bacillus cereus ZY-2009. It grew normally in the media containing 10-100 mg/L Cr(VI), indicating its high resistance to Cr(VI). Under the optimal conditions of pH 7.0, inoculation amount 10%, and temperature 30 degrees C, Cr(VI) was effectively removed, with a removal rate of similar to 80%. Co-existing Fe3+ and Cu2+ greatly increased Cr(VI) removal, but Cd2+ showed significant inhibition. Cr(VI) was removed mainly via enzyme-mediated bioreduction but not biosorption. Cr(VI) was reduced by different cell fractions (i.e. extracellular secretions, cytoplasm, and cell envelope), implying that Cr(VI) can be reduced both extracellularly and intracellularly. This strain can be used in the bioremediation of Cr(VI)-containing wastewater, with Fe3+ and Cu2+ as stimulators.

Automated summary

A strain of Cr(VI)-resistant bacterium, identified as Bacillus cereus ZY-2009, showed high tolerance to Cr(VI) and effectively removed Cr(VI) through enzyme-mediated bioreduction. Co-existing Fe3+ and Cu2+ enhanced Cr(VI) removal, while Cd2+ inhibited it. This strain has potential for bioremediation of Cr(VI)-containing wastewater with Fe3+ and Cu2+ as stimulators.