Arsenite oxidation by a facultative chemolithotrophic Delftia spp. BAs29 for its potential application in groundwater arsenic bioremediation

A superior arsenite [As (III)] oxidizing strain was isolated by enrichment technique from a shallow aquifer of Bhojpur district, Bihar, India. Along with high As (III) and arsenate [As (V)] resistance [up to 70 mM of As (III) and 1000 mM of As (V), respectively], it showed high resistance to multi-metals and a superior ability to utilize a wide range of carbon sources. The gram-negative rod-shaped strain of Delftia spp. BAs29 was characterized thoroughly for its As (III) oxidation ability. The strain showed mixed growth associated, facultative chemolithotrophic As (III) oxidation process, releasing-67 kJ/reaction of free energy in an exergonic reaction. Testing of cost-effective and natural bio-sorbents showed efficient As (V) removal from the contaminated water. Moringa oleifera showed the maximum As (V) removal capacity of 57.89% among the tested bio-sorbents. This study revealed a two-step approach for arsenic removal with 98.77% efficiency from groundwater using an indigenous As (III) oxidizing strain combined with a natural bio-sorbent.