Cobalt separation by Alphaproteobacterium MTB-KTN90: magnetotactic bacteria in bioremediation.

Abstract

Bioremediation of toxic metals by magnetotactic bacteria and magnetic separation of metal-loaded magnetotactic bacteria are of great interest. This bioprocess technique is rapid, efficient, economical, and environmentally friendly. In this study, cobalt removal potential of a novel isolated magnetotactic bacterium (Alphaproteobacterium MTB-KTN90) as a new biosorbent was investigated. The effects of various environmental parameters in the cobalt removal and the technique of magnetic separation of cobalt-loaded bacterial cells were studied. Cobalt removal by MTB-KTN90 was very sensitive to pH solution; higher biosorption capacity was observed around pH 6.5-7.0. When biomass concentration increased from 0.009 to 0.09g/l, the biosorption efficiency increased from 13.87% to 19.22%. The sorption of cobalt by MTB-KTN90 was rapid during the first 15min (859.17mg/g dry weight). With the increasing of cobalt concentrations from 1 to 225mg/l, the specific cobalt uptake increased. Maximum cobalt removal (1160.51±15.42mg/g dry weight) took place at optimum conditions; pH 7.0 with initial cobalt concentration of 115mg/l at 60min by 0.015g/l of dry biomass. The results showed maximum values for constants of Langmuir and Freundlich models so far. The biosorption mechanisms were studied with FTIR, PIXE, and FESEM analysis. Cobalt-loaded MTB-KTN90 had ability to separate from solution by a simple magnetic separator. Magnetic response in MTB-KTN90 is due to the presence of unique intracellular magnetic nanoparticles (magnetosomes). The orientation magnetic separation results indicated that 88.55% of cobalt was removed from solution. Consequently, Alphaproteobacterium MTB-KTN90 as a new biosorbent opens up good opportunities for the magnetic removal of cobalt from the polluted aquatic environments.