Removal Performance and Pathways of Chromium (Vi) by Bacillus Cereus Fnxj1-2-3 and its Potential Bioremediation in Co-Contaminants Cr (Vi) and Ni (Ii) Wastewater

Abstract

Bacillus cereus FNXJ1-2-3, a nickel-resistant bacterium, exhibited about 80% removal efficiency of Cr(VI) under suitable conditions (~34 °C, pH 7.0-8.0, initial Cr(VI) concentration ~30 mg/L, and initial cell density after incoulation~4.5*10 8 cells/mL). The removal and adsorption behavior of Cr(VI) by FNXJ1-2-3 strain followed the first-order kinetics and the pseudo-second-order kinetics, respectively. Comprehensive analysis of the results of Zeta potential, FTIR, and XPS etching characterizations, the excellent adsorption capacity and the strong reducibility were believed to be responsible for the high removal efficiency. Both outside and inside of the FNXJ1-2-3 strain cell, the chemical states of Cr species were dynamic and underwent a following detoxification route of Cr(VI)→Cr(III)→metallic Cr(0) with at least two detoxification extracellular and intracellular enzymes (E Cr VI → III and E Cr III → 0 ) existing and the main final form of intracellular and extracellular chromium is Cr(III). Furthermore, Bacillus cereus FNXJ1-2-3 also had strong removal performance to Cr(VI) even the wastewater containing both Cr(VI) and Ni(II) species for its excellent selective resistance to Ni(II). Therefore, Bacillus cereus FNXJ1-2-3 may be a promising candidate strain in multi-metal mixed industrial wastewater treatment.

Keywords: Bacillus cereus FNXJ1-2-3, Cr(VI)-removal, Cr(VI)-biosorption, Cr(VI)-bioreduction, nickel-resistant.