Arsenic sequestration by manganese-oxidizing <i>Acinetobacter </i> sp.

Abstract

This paper presents the potential of manganese (Mn)-oxidizing bacteria in removing arsenic from synthetic solution. Mn-oxidizing bacterium was isolated from arsenic and manganese contaminated ground water from district Ballia (UP), India. The bacterium was identified as <i>Acinetobacter </i> sp. by the Institue of Microbial Technology, Chandigarh, India. Synthetic solution of Mn (25 ppm) was treated with <i>Acinetobacter</i> sp. (20 mg/mL) biomass in neutral pH (7.0) at ambient temperature. <i>Acinetobacter </i> sp. was found efficient to oxidize 44.04% (11.01 ppm) Mn within 2 h. Kinetics of Mn oxidation showed that maximum velocity (Vmax) for Mn oxidation was 16.69 µM mg^-1 h^-1, while kinetic constant (Km) was found to be 1.09 mM. Mn oxidation by <i>Acinetobacter </i> sp. follows the Michalis-Menten kinetics. Free and immobilized cells of Mn-oxide laden <i> Acinetobacter </i> sp. was used for removal of arsenite [As(III)] from arsenite contaminated water. Free and immobilized cells of Mn-oxide (11.01 ppm) laden <i> Acinetobacter </i>sp<i>.</i> biomass (20 mg/mL) was effective in removing of 0.760 ppm arsenite within 30 min and 3.39 ppm arsenite within 15 min from 5 ppm As(III) containing synthetic solution at pH 7. The immobilized cells of Mn-oxide laden <i> Acinetobacter </i> sp. were found to be 4.46 times more effective for the removal of As(III) as compared to the free cells.