Comparative evaluations on bio-treatment of hexavalent chromate by resting cells of Pseudochrobactrum sp. and Proteus sp. in wastewater

Two marine bacterial strains, B5 and H24, were isolated from long-term Cr(VI) contaminated seawater and identified as Pseudochrobactrum and Proteus, respectively, based on 16S rRNA gene sequence analyses. Both strains were examined for their tolerance to Cr(VI) and other metal salts and their abilities to reduce Cr(VI) to trivalent chromium [Cr(III)]. Growing cells of Pseudochrobactrum sp. B5 and Proteus sp. H24 could tolerate Cr(VI) at a concentration of 2000 and 1500mg/l and completely reduce 1000mg/l Cr(VI) in LB medium within 96 and 144h, respectively. Resting cells of the two strains were able to reduce 200mg/l Cr(VI) in Tris–HCl buffer within 16 and 24h, respectively. Furthermore, resting cells of both strains were able to reduce Cr(VI) in industrial wastewaters three times consecutively. Overall, this study provides evidence of the potential for application of chromate-reducing bacteria to direct Cr(VI) decontamination of industrial effluents. •Two chromate(VI) reducing bacterial strains, B5 and H24, were isolated from seawater.•Strains B5 and H24 belonged to genera Pseudochrobactrum and Proteus.•Resting cells of B5 and H24 successfully removed Cr(VI) from wastewater repeatedly.•Pseudochrobactrum sp. B5 was superior to Proteus sp. H24 at Cr(VI) reduction.