Manganese Removal Using Several Managanse-resistant Bacteria

In this study, we collected some soil samples from Zn-Mn Mine in Hunan and manganese storage of Ma-steel factory in Tianjin, from which seven Mn(II)-removing bacterial strains were separated. We defined the bacteria which can oxidize soluble Mn(II) into insoluble Mn oxides are Mn(II)-oxidizing bacteria, and they are kd and MK3-1. The bacteria which can transform the soluble Mn(II) into insoluble MnCO3 as the Mn(II)-removing bacteria, namely, J4-3,J12-1,JM3-2,J2-3 and JD. The results of 16S rRNA gene analysis showed that the Mn(II)-oxidizing bacteria all belong to Bacillus and the Mn(II)-removing bacteria can be respectively categorized as Mycobacterium, Rhodococcus opacus, Acinetobacter, Hydrogenophaga and Bacillus.The results of scan electron microscope of Mn(II)-oxidizing bacteria showed that the superficial structures and the size of Mn(II)-oxidizing bacteria have no obvious change under the cultivation conditions with or without Mn, but the cell's surface was covered by Mn oxides after the Mn(II)-oxidation. Energy spectrum analysis showed that the content of manganese of cell surfaces of the MK3-1 was 19.60%(W/W). A 903 bp multicopper oxidase gene mnxG encoding the putative Mn(II)-oxidizing protein was amplified by PCR. The product of mnxG sequence showed a 86% identity to the MnxG (AAZ31739) which amplified from the Bacillus sp. GB02-16. kd and MK3-1 had strong ability of Mn-resistance with MIC of 50 mmol/L and 20 mmol/L, respectively. The results showed that they were able to oxidize and remove more than 88% and 96% of Mn(II) in the culture medium, respectively. The immobilized solid-embedding kd and MK3-1 cells can remove 62% and 85% of Mn(II) from artificial Mn(II) contaminated water. Although the Mn(II)-removal efficiency had declined, it is still stable.The results of scan electron microscope showed that the superficial structures and the size of Mn(II)-removing bacteria have no obvious change under the cultivation conditions with or without Mn. Energy spectrum analysis indicated that the content of manganese on the cell surface of Mn(II)-removing bacteria is 0. The X-Ray Diffractomer (XRD) results showed that the dark brown precipitate formed from the Mn(II)-removing bacteria is MnCO3. The results of Mn(II)-resistant tests indicated that the Mn(â…¡)-removing bacteria cultivated in the J medium were 12 mmol/L for J21-1, J2-3 or J4-3, and 2 mmol/L for JD and JM3-2. The results indicated that the Mn(â…¡)-removing bacteria were effective in removing Mn(â…¡) under the condition of medium in which more than 85%Mn(â…¡) was removed.This study provides valuable of Mn(â…¡)-oxidizing bacteria, Mn(â…¡)-removing bacteria, the immobilized solid-embedding of bacteria and basic knowledges for further applications on bioremediation of Mn(â…¡)-contaminated water system.