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KMID : 0364820090450040411
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Korean Journal of Microbiology
2009 Volume.45 No. 4 p.411 ~ p.415
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Bioleaching of Mn(II) from Manganese Nodules by Bacillus sp. MR2
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Choi Sung-Chan
Lee Ga-Hwa
Lee Hong-Kum
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Abstract
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Some microorganisms are capable of leaching Mn(II) from nonsulfidic manganese ores indirectly via nonenzymatic
processes. Such reductive dissolution requires organic substrates, such as glucose, sucrose, or galactose,
as a source of carbon and energy for microbial growth. This study investigated characteristics of Mn(II) leaching from manganese nodules by using heterotrophic Bacillus sp. strain MR2 provided with corn starch as a less-expensive substrate. Leaching of Mn(II) at 25.6 g Mn(II) kg-1 nodule day-1 was accompanied with cell growth, but part of the produced Mn(II) re-adsorbed onto residual MnO2 particles after 24 h. Direct contact of cells to manganese nodule was not necessary as a separation between them with a dialysis tube produced similar amount [24.6 g Mn(II) kg-1 nodule day-1]. These results indicated an involvement of extracellular diffusible compound(s) during Mn(II) leaching by strain MR2. In order to optimize a leaching process we tested factors that influence the reaction, and the most efficient conditions were 25~35oC, pH 5~7, inoculum density of 1.5~2.5% (v/v), pulp density of 2~3 g/L, and particle size <75 μm. Although Mn(II) leaching was enhanced as particle size decrease, we suggest <212 μm as a proper size range since more grinding means more energy consumption. The results would help for the improvement of bioleaching of manganese nodule as a less expensive, energy-efficient, and environment-friendly technology as compared to the existing physicochemical metal
recovery technologies.
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KEYWORD
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Bacillus, bioleaching, manganese nodule, reductive dissolution
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