Fungal solubilization of manganese oxide and its significance for antimony mobility

• Fungi transform manganese oxide (hausmannite) to biogenic oxalate (lindbergite).
• Antimony has high affinity towards hausmannite with up to 76% adsorption efficiency.
• Hausmannite solubilization mobilizes adsorbed Sb and favors its bioaccumulation.
• Presence of manganese minerals significantly increases fungal resistance to Sb.

Antimony and many other potentially toxic metals and metalloids are transformed and mobilized in the environment by fungal metabolic activity directly by bioaccumulation and biovolatilization and indirectly by bioleaching of natural metal scavengers such as manganese oxides. This fungal contribution on antimony geochemistry is highlighted in this paper which assessed pre-adsorbed antimony release from manganese oxides in a 14-day Aspergillus niger cultivation. Biotransformation of manganese oxide was determined by X-ray powder diffraction analysis (XRD), and fungal antimony bioaccumulation and biovolatilization was assessed by flame atomic absorption spectrometry. XRD analysis identified the manganese oxides as hausmannite which dissolved during 14-day Aspergillus niger cultivation and was transformed to manganese oxalate - lindbergite. This newly formed mycogenic manganese mineral caused no impedance to antimony mobilization because of its low sorption capacity. Due to rapid manganese biotransformation, almost 99% antimony was desorbed from the manganese mineral surface. Antimony mobilization was further enhanced by fungal volatilization. This concludes that enhanced activity of microscopic filamentous fungi significantly increases mobility of antimony. Our findings contribute to understanding of antimony and manganese oxide interactions in the presence of filamentous fungi.

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