Bioremoval of hexavalent chromium from water by a salt tolerant bacterium, Exiguobacterium sp. GS1

Abstract

Pollution of terrestrial surfaces and aquatic systems by hexavalent chromium, Cr(VI), is a worldwide public health problem. A chromium resistant bacterial isolate identified as Exiguobacterium sp. GS1 by 16S rRNA gene sequencing displayed high rate of removal of Cr(VI) from water. Exiguobacterium sp. GS1 is 99% identical to Exiguobacterium acetylicum. The isolate significantly removed Cr(VI) at both high and low concentrations (1-200 μg mL-1) within 12 h. The Michaelis-Menten K m and V max for Cr(VI) bioremoval were calculated to be 141.92 μg mL -1 and 13.22 μg mL-1 h-1, respectively. Growth of Exiguobacterium sp. GS1 was indifferent at 1-75 μg mL-1 Cr(VI) in 12 h. At initial concentration of 8,000 μg L-1, Exiguobacterium sp. GS1 displayed rapid bioremoval of Cr(VI) with over 50% bioremoval in 3 h and 91% bioremoval in 8 h. Kinetic analysis of Cr(VI) bioremoval rate revealed zero-order in 8 h. Exiguobacterium sp. GS1 grew and significantly reduced Cr(VI) in cultures containing 1-9% salt indicating high salt tolerance. Similarly the isolate substantially reduced Cr(VI) over a wide range of temperature (18-45°C) and initial pH (6.0-9.0). The T opt and initial pHopt were 35-40°C and 7-8, respectively. Exiguobacterium sp. GS1 displayed a great potential for bioremediation of Cr(VI) in diverse complex environments. © 2008 Society for Industrial Microbiology.