Isolation of arsenite-oxidizing bacteria from industrial effluents and their potential use in wastewater treatment

The present study is aimed at assessing the ability of Klebsiella pneumoniae and Klebsiella variicola to oxidize trivalent arsenic into its pentavalent form. K. pneumoniae could tolerate As(III) (26.6 mM) and K. variicola could tolerate As(III) (24 mM). K. pneumoniae was able to resist Cd²⁺ and Hg²⁺ (1.3 mM), Cr⁶⁺ and Cu²⁺ (6.6 mM) and Ni²⁺ (5.3 mM). K. variicola resisted Cd²⁺ (2.6 mM), Hg²⁺ (4 mM), Cr⁶⁺ (6.6 mM), Cu²⁺ (9.3 mM) and Ni²⁺ (5.3 mM). The optimum temperature and pH for K. pneumoniae and K. variicola were 7 and 30°C, respectively. K. pneumoniae could oxidize 36% As(III), 64% and 87% from the medium after 24, 48 and 72 h, respectively. Likewise K. variicola was also able to oxidize 33% As(III) after 24 h, 59% after 48 h and 83% after 72 h from the medium. The presence of an induced protein having molecular weight around 14 kDa in the presence of arsenic points out a possible role of this protein in arsenite oxidation. The bacterial isolates can be employed to bioremediate As-containing wastes.