Fungal transformation of natural and synthetic cobalt-bearing manganese oxides and implications for cobalt biogeochemistry.

John Ferrier,Geoffrey Michael Gadd,Laszlo Csetenyi

doi:10.1111/1462-2920.15526

John Ferrier, Geoffrey Michael Gadd + Show 1 more

Open Access

https://doi.org/10.1111/1462-2920.15526

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Abstract

Manganese oxide minerals can become enriched in a variety of metals through adsorption and redox processes, and this forms the basis for a close geochemical relationship between Mn oxide phases and Co. Since oxalate-producing fungi can effect geochemical transformation of Mn oxides, an understanding of the fate of Co during such processes could provide new insights on the geochemical behaviour of Co. In this work, the transformation of Mn oxides by Aspergillus niger was investigated using a Co-bearing manganiferous laterite, and a synthetic Co-doped birnessite. A. niger could transform laterite in both fragmented and powder forms, resulting in formation of biomineral crusts that were composed of Mn oxalates hosting Co, Ni and, in transformed laterite fragments, Mg. Total transformation of Co-doped birnessite resulted in precipitation of Co-bearing Mn oxalate. Fungal transformation of the Mn oxide phases included Mn(III,IV) reduction by oxalate, and may also have involved reduction of Co(III) to Co(II). These findings demonstrate that oxalate-producing fungi can influence Co speciation in Mn oxides, with implications for other hosted metals including Al and Fe. This work also provides further understanding of the roles of fungi as geoactive agents which can inform potential applications in metal bioremediation, recycling and biorecovery.

Highlights

Mn oxides are ubiquitous in terrestrial and aquatic environments and occupy a central role in a range of biogeochemical processes
Manganese oxide minerals can become enriched in a variety of metals through adsorption and redox processes, and this forms the basis for a close geochemical relationship between Mn oxide phases and Co
A. niger could transform laterite in both fragmented and powder forms, resulting in formation of biomineral crusts that were composed of Mn oxalates hosting Co, Ni and, in transformed laterite fragments, Mg

Summary

Introduction

Mn oxides are ubiquitous in terrestrial and aquatic environments and occupy a central role in a range of biogeochemical processes. Newsome et al (2020) showed that Co mobility in anaerobic laterite sediment microcosms was closely related to Mn release which was primarily attributed to indigenous Mn(IV) and Fe(III) reducing bacteria. This points to a direct relationship between Mn(III,IV) oxide mineral dissolution and Co mobility, and that anaerobic prokaryotes occupy an important role in such processes. Little information exists on the fate of Co as a result of fungal interactions with Mn oxides, or fungal interactions with Co generally This is surprising given the capacity of several fungal species to precipitate This is surprising given the capacity of several fungal species to precipitate (e.g. Acremonium sp., Stagonospora sp. and Pyrenochaeta sp.) or solubilize Mn oxides (e.g. Aspergillus niger, Serpula himantioides), and the

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