Simultaneous biotreatment of hexavalent chromium Cr(VI) and polychlorinated biphenyls (PCBs) by indigenous bacteria of Co-polluted wastewater

Abstract

The study was designed to isolate, identify, and characterize bacterial strains potentially capable for simultaneous biotransformation of hexavalent chromium (Cr(VI)) and polychlorinated biphenyl (PCBs) from co-contaminated site. Around 150 isolates from industrial wastewater were isolated through enrichment of minimal salt medium (MSM) with 2 mg L−1 Cr(VI). Strains capable of reducing Cr(VI) were acclimatized for biphenyl and 2-chorobiphneyl degradation by media amendment with yeast extract and biphenyl (10:90). Maximum Cr(VI) reduction was achieved in MSM at varying concertation with an average of 78% at 2 mg L−1 concentration whereas 74% Cr(VI) reduction was observed in yeast biphenyl MSM. Bacterial strains were characterized for average growth rate, doubling time, colony forming units and time to steady state. Three most efficient strains i.e., SB, K7 and K8, were identified as Pseudomonas aeruginosa (SB), Pseudomonas pseudoalcaligenes (K7), Stenotrophomonas maltophilia (K8). GC-MS analysis showed that strain K8 has significantly higher degradation potential for 2-CB and biphenyl (81% & 91% respectively), when treated individually. In simultaneous experiment, strains K7 and SB degraded 57% and 49% 2-CB respectively, whereas 56% and 55% Cr(VI) was transformed by both strains in 120 h of incubation. Results of this study showed the potential of selected bacterial strains for simultaneous treatment of Cr(VI) and PCBs in water bodies.