Identification and hexavalent chromium reduction characteristics of Pannonibacter phragmitetus

A hexavalent chromium [Cr(VI)] reducing bacterial strain was isolated from chromium-containing slag. It was identified as Pannonibacter phragmitetus based on physiological, biochemical characteristics and 16S rRNA gene sequence analysis. This bacterium displayed great Cr(VI) reduction capability. The Cr(VI) could be completely removed in 24 h under anaerobic condition when the initial concentration was 1,917 mg L(-1), with the maximum reduction rate of 562.8 mg L(-1) h(-1). The Cr(VI) reduction rate increased with the increase of Cr(VI) concentration. P. phragmitetus was able to use many carbon sources such as lactose, fructose, glucose, pyruvate, citrate, formate, lactate, NADPH and NADH as electron donors, among which the lactate had the greatest power to promote the reduction process. Zn(2+), Cd(2+) and Ni(2+) inhibited, while Cu(2+), Pb(2+), Mn(2+) and Co(2+) stimulated the reduction. The optimum pH and temperature for reduction were 9.0 and 30 °C, respectively. The results indicated that this strain had great potential for application in the bioremediation of chromate-polluted soil and water systems.