There is a significant presence of Mn-II in terrestrial and marine environments that can beoxidized from soluble manganese (Mn-II) into insoluble Mn-III/IV by bacteria. The Mn oxides play an important role in the fate of other vital elements that are required for different biogeochemical reactions such as carbon, sulfur, iron, and others. The oxidation mechanism employed by bacteria is unclear. The marine bacterium Erythrobactersp. SD-21 is known to produce a Mn-oxidizing protein called MopA. This protein has the potential to be utilized in the field of bio remediation focusing on the treatment of contaminated sources. Previous purification attempts have provided samples of heterologously expressed MopA with incomplete purification or no activity. The purpose of this project is to derive an active and pure sample of MopA through different purification methods. The current purification protocol involves nickel affinity chromatography with a desalting process. Such a method has provided an active but not so pure sample of MopA. Additional purification by an ion exchange chromatography is being investigated. The 250-kDa native MopA is identified by SDS-PAGE. Mn oxidizing activity is quantified through a colorimetric LBB assay and the concentration of the protein is determined by absorbance. Additional purification will allow future studies on the mechanism of Mnoxidation by MopA.