Reduction of hexavalent chromium (VI) by indigenous alkaliphilic and halotolerant Microbacterium sp. M5: comparative studies under growth and nongrowth conditions.

Abstract

To evaluate hexavalent chromium (Cr (VI)) reduction potential of indigenous isolate M5, under growing and nongrowing conditions. Microbacterium sp. M5 was isolated from soil samples collected from a common effluent treatment plant, after enrichment of indigenous microbial diversity in the presence of 200mgl-1 of Cr (VI). The isolate achieved complete reduction of 400mgl-1 Cr (VI) supplement to Luria Bertani medium having initial pH of 9·0 after 48h incubation. Furthermore, the reduction potential of resting and surfactant treated cell membrane compromised cells of M5 was evaluated. The control and biosurfactant treated cells achieved 22·71±0·5% and 40·56±0·5% reduction of 50mgl-1 Cr (VI) in Tris-HCl buffer, under resting cells conditions. To the best of our knowledge, this is the first report where cells with compromised cell membrane obtained after exposure to biosurfactant have been evaluated for Cr (VI) reduction. The Cr (VI) reduction potential of Microbacterium sp. M5 could be effectively exploited for treatment of chromium-rich effluents, under nongrowing conditions. The isolate M5 could be a potential inoculum for effluent treatment plants as it is able to support Cr (VI) reduction under wide range of pH, salinity and in the presence of different metal ions.