Reduction of hexavalent chromium by Ochrobactrum intermedium BCR400 isolated from a chromium-contaminated soil

Hexavalent chromium-resistant Ochrobactrum intermedium BCR400 was isolated from chromium contaminated soil collected from Vadodara, Gujarat. It reduced 100 mg Cr(VI)/L completely in 52 h with initial Cr(VI) reduction rate of 1.98 mg/L/h. The Cr(VI) reduction rate decreased with increase in Cr(VI) concentration from 100 to 500 mg/L. The addition of anthraquinone-2-sulphonic acid (AQS) to culture O. intermedium BCR400 significantly enhanced its chromium reduction rate. The activation energy of AQS-mediated Cr(VI) reduction (120.69 KJ/mol) was 1.1-fold lower than non-mediated Cr(VI) reduction. An increase in the activities of quinone reductase and chromate reductase in cells grown in presence of AQS/AQS + Cr(VI) suggests their role in reduction of Cr(VI) by O. intermedium. Both chromate reductase and quinone reductase activities were FAD independent, required NADH as reductant, displayed maximum activity at pH (7.0) and temperature (30 °C). Thus Cr(VI) bioremediation potential of O. intermedium can be enhanced by augmentation of system with AQS as redox mediator.