Anaerobic reduction of hexavalent chromium by bacterial cells of Achromobacter sp. Strain Ch1

SummaryHexavalent chromium [Cr(VI)] is a widespread environmental contaminant. Achromobacter sp. strain Ch1 was a Cr(VI) reducing bacterium with high reduction performance. Cr(VI) reductase was just existing in the cells, but was not discharged into the surrounding medium. Cr(VI) reduction was carried out with resting cells of strain Ch1 under anaerobic conditions. Initial pH value and lactate (electron donor) concentration were found to influence the reduction rate of Cr(VI), and the optimal conditions were at pH 9.0 and supplemented with 40 mM of lactate. The reduction rate would be constant under established conditions approximately 12.5 μmol 109 cells−1 min−1, which was not affected by cell density and initial Cr(VI) concentration. The maximal reduction capacity of Achromobacter sp. strain Ch1 was 54.2 mM, while the cell density of reduction system was 3.64×109 cells ml−1. Energy-dispersive X-ray (EDX) analysis showed that chromium was precipitated perhaps as the form of Cr(OH)3.