Bioleaching of Manganese from Ferromanganese Nodules Utilizing Acetogenic Bacteria in a Symbiotic Community of Bacteria and Yeast

Increased global demand for manganese has led to renewed interest in the development of sustainable and cost-effective methods for the utilization of low-grade manganese resources. Bioleaching approaches that use microorganisms to extract metals from ores are an intriguing alternative processing method that has been widely employed for numerous other mineral resources. In this study, we investigated the ability of acetogenic bacteria within a symbiotic community of bacteria and yeast (SCOBY) cultured from commercially available kombucha and vinegar food products to leach manganese from a low-grade ore composed of ferromanganese nodules. We found that kombucha-derived SCOBYs extracted up to 26.3% of total manganese from the ore in twelve days and was selective against the leaching of iron (< 0.66% of total iron leached). Increased extraction rates by kombucha-derived SCOBYs were observed with stirring and staggered addition of ore to the leach media. In contrast, vinegar-derived SCOBYs leached lower concentrations of manganese from the ore (maximum of 3.1% of total manganese leached) under all conditions. Optimal leaching was observed using kombucha-derived SCOBYs with staggered addition of ore. The difference in leaching efficiencies between the SCOBYs is hypothesized to result from differences in the microbial community's ability to withstand harsh environmental conditions present in the media during leaching. Further work to optimize conditions for acetic acid production and ore upgradation processes may also improve leaching efficiencies and rates.