Colonization and bioweathering of monazite by Aspergillus niger: solubilization and precipitation of rare earth elements

Abstract

Geoactive fungi play a significant role in bioweathering of rock and mineral substrates. Monazite is a phosphate mineral containing the rare earth elements (REE) cerium, lanthanum and neodymium. Little is known about geomicrobial transformations of REE-bearing minerals which are also relevant to REE biorecovery from terrestrial and extra-terrestrial reserves. The geoactive soil fungus Aspergillus niger colonized monazite in solid and liquid growth media without any apparent growth inhibition. In a glucoseminerals salts medium, monazite enhanced growth and mycelium extensively covered rock particle surfaces, probably due to the provision of phosphate and essential trace metals. Teeth-like and pagoda-like etching patterns indicated monazite dissolution, with extensive precipitation of secondary oxalate minerals. Biomechanical forces ensued causing aggressive bioweathering effects by tunnelling, penetration and splitting of the ore particles. High amounts of oxalic acid ($46 mM) and moderate amounts of citric acid ($5 mM) were produced in liquid media containing 2% (wt./vol.) monazite, and REE and phosphate were released. Correlation analysis suggested that citric acid was more effective than oxalic acid in REE mobilization, although the higher concentration of oxalic acid also implied complexant activity, as well as the prime role in REE-oxalate precipitation.

Astrobiology of life on Earth

“…In the current special issue, Kang et al . (2021) now examine the influence of Aspergillus niger on the weathering of monazite, a phosphate‐mineral source of rare earth elements such as Ce, La and Nd. Culture‐based studies that involved addition of monazite to the growth medium were used to unravel the biophysical/biogeochemical process of rock degradation by this ascomycete, including the production of organic acids such as citric acid and oxalic acid.…”

“…Kang et al . (2021) provides fundamental knowledge on the microbial processing and potential utilization of these important elements on Earth and potentially on other planetary bodies in the future.…”

Solubilization of struvite and biorecovery of cerium by Aspergillus niger

“…Microbial biomineralization has been taken advantage of in recent years because of its environmentally friendly nature and cost-effectiveness, and therefore has potential applications for the removal of environmental pollutants and the recovery of precious metals from wastes (Liang and Gadd 2017;Yang et al 2019;Li et al 2020a,b;Xu et al 2020). Geoactive fungi play an important role in the biomineralization of a broad range of minerals and have been investigated for their potential in the recycling of elements and biosynthesis of new biomaterials (Gadd 2007;Liang and Gadd 2017;Kang et al 2020Kang et al , 2021. The fundamental mechanisms behind fungal biomineralization involve the production of metabolites such as oxalate and carbon dioxide, or the release of ligands like carbonates and phosphates from organic and inorganic sources, as well as proteins and enzymes that can directly interact with the metal/mineral (Gadd 2007(Gadd , 2010Li et al 2014;Kumari et al 2016;Dhami et al 2017;Fomina et al 2007;Liu et al 2019;Kirtzel et al 2020;Kang et al 2020Kang et al , 2021Mendes et al 2021a,b;Liu et al 2021).…”

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

“…Factors that determine soluble complex formation or oxalate precipitation include the valence state of the cation, the relative abundance of oxalate anions and metals in solution, pH and stability constants of the oxalate complexes (Gadd, 1999;Verma et al, 2019) For example, simple oxalates containing divalent cations are sparingly soluble or insoluble and readily precipitate over a wide range of pH values (e.g. Ca, Mg, Mn, Co, Ni, Cu) but may also form complexes in the presence of excess oxalate, while trivalent metals such as Al(III) and Fe(III) only exist as soluble complexes (Gadd, 1999;Gadd et al, 2014;Verma et al, 2019;Kang et al, 2019Kang et al, , 2020Kang et al, , 2021Mendes et al, 2020). In addition, oxalate is a reductant which can effect the reduction of some metal species, including Mn(III,IV) to Mn(II), through oxalate precipitation (Wei et al, 2012;Verma et al, 2019).…”