Optimum pH for oxidation of Mn(II) ions in model and actual manganese drainages by a Mn-oxidizing fungus, Phoma sp. strain KY-1

A Mn-oxidizing fungus, Phoma sp. strain KY-1, showed a Mn-oxidizing activity of more than 1.82 mol m^-3 of Mn(II) at an optimum pH 6.8. Controlling the pH at between 6.5 and 7.3 was necessary for fungal oxidation of Mn(II). This is probably due to inactivation of the Mn-oxidizing enzyme by decrease in pH during the reaction. Carbon fiber was found to catalyze the oxidation of Mn(II), most significantly under more unfavorable conditions such as high Mn concentrations, coexisting inhibitive components, or lacking nutrients. Examinations of fungus used for actual Mn-rich mine drainage containing more than 1.46 mol m^-3 of Mn showed that organic nourishments and pH-buffering agents are both essential to obtain acceptable Mn removal rates and that the time required to attain the 10 mg dm^-3 (0.182 mol m^-3), which is the maximum acceptable concentration of Mn in discharged wastewater in Japan, was about 170h in the presence of carbon fiber.