Manganese(II) oxidation by the multi-copper oxidase CopA from Brevibacillus panacihumi MK-8

Manganese contamination of groundwater exists worldwide. Manganese removal is primarily performed through catalytic oxidation by manganese-oxidizing bacteria. In this study, we identified a new manganese(II) oxidase (CopA) from Brevibacillus panacihumi MK-8. The copA gene was cloned and expressed in Escherichia coli strain BL21(DE3), and the recombinant strain BL21-pET-copA was able to remove 85.87% of Mn(II) from LB medium containing 1 mM Mn(II) after seven days. The optimum Mn(II) oxidase CopA activity was obtained at 37 °C in 10 mM HEPES buffer (pH 8.0) containing 0.4 mM CuCl2. Purified CopA removed 51.98% of manganese(II) under the optimal conditions. The copA gene-deleted strain (MK-8-ΔcopA) barely oxidized manganese, further demonstrating that the copA gene is the manganese oxidase gene. Biogenic Mn oxides were analyzed by scanning electron microscopy and X-ray diffraction. Thus, we suggest that the recombinant BL21-pET-copA strain and oxidase CopA have the potential to be used in biological manganese removal technology.