Indirect Manganese Removal byStenotrophomonassp. andLysinibacillussp. Isolated from Brazilian Mine Water

Abstract

Manganese is a contaminant in the wastewaters produced by Brazilian mining operations, and the removal of the metal is notoriously difficult because of the high stability of the Mn(II) ion in aqueous solutions. To explore a biological approach for removing excessive amounts of aqueous Mn(II), we investigated the potential of Mn(II) oxidation by both consortium and bacterial isolates from a Brazilian manganese mine. A bacterial consortium was able to remove 99.7% of the Mn(II). A phylogenetic analysis of isolates demonstrated that the predominant microorganisms were members ofStenotrophomonas,Bacillus, andLysinibacillusgenera. Mn(II) removal rates between 58.5% and 70.9% were observed forBacillussp. andStenotrophomonassp. while theLysinibacillusisolate 13P removes 82.7%. The catalytic oxidation of Mn(II) mediated by multicopper oxidase was not properly detected; however, in all of the experiments, a significant increase in the pH of the culture medium was detected. No aggregates inside the cells grown for a week were found by electronic microscopy. Nevertheless, an energy-dispersive X-ray spectroscopy of the isolates revealed the presence of manganese inStenotrophomonassp. andLysinibacillussp. grown in K medium. These results suggest that members ofStenotrophomonasandLysinibacillusgenera were able to remove Mn(II) by a nonenzymatic pathway.