| Research Abstract |
A Mn-oxidizing fungus has been isolated from Mn-deposits around the hot spring in the southern part of Hokkaido, and identified to be Phoma sp.based on morphology, physiology, and genetics. The fungus oxidizes Mn(II) ions at neutral pHs and the optimum pH was 6.8. With decrease in organic carbon sources in the mediaum, Mn(II) oxidation rate was increased. The fungal Mn(II) oxidation required peptone and yeast extract as carbon sources, and the rate were delayed by the addition of glucose. Maximum Mn(II) limit for the fungal oxidation was 120ppm, which is in the range of Mn concentrations in actual mine drainage. The PAN type of carbon fiber has clearly enhanced the fungal Mn(II) oxidation rate, and improved the transparency of the solution. The PET fiber, which has the same diameter and length, did not work similarly. This might be caused by bio-affinity of carbon fiber.
The biogenic Mn-oxides were identified to be γ-MnO_2 (ramsdellite) by XRD. According to SEM observation, the biogenic Mn-oxides were porous with 4nm in an average diameter, and the pore sizes were more sharply distributed in the presence of carbon fiber. Carbon fiber might stabilize the crystal growth induced by the fungus. The porous γ-MnO_2 has the possibility for application to battery materials in addition to the second mine drainage treatment.
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