Rare earth element sequestration by Aspergillus oryzae biomass

ABSTRACT

The fungus Aspergillus oryzae could be shown to be a viable alternative for biosorption of valuable metals from solution. Fungal biomass can be obtained easily in high quantities as a waste of biofermentation processes, and used in a complex, multi-phase solution mimicking naturally occurring, mining-affected water samples. With test solution formulated after natural conditions, formation of secondary Al and Fe phases co-precipitating Ce was recorded in addition to specific biosorption of rare earth elements. Remarkably, the latter were removed from the solution despite the presence of high concentrations of interfering Fe and Al. The biomass was viable even after prolonged incubation in the metal solution, and minimal inhibitory concentrations for single metals were higher than those in the test solution. While precipitation/biosorption of Ce (maximal biosorption efficiency was 58.0 ± 22.3% after 6 h of incubation) coincided with the gross removal of Fe from the metal solution, Y (81.5 ± 11.3% efficiency, 24 h incubation) and Nd (87.4 ± 9.1% efficiency, 24 h incubation) were sequestered later, similarly to Ni and Zn. The biphasic binding pattern specific to single metals could be connected to dynamically changing pH and NH₄⁺ concentrations, which were attributed to the physiological changes taking place in starving A. oryzae biomass. The metals were found extracellularly in minerals associated with the cell wall, and intracellularly precipitated in the vacuoles. The latter process was explained with intracellular metal detoxification resulting in metal resistance.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biosorption
• biomining
• bioremediation
• uranium mine
• rare earth metals

Acknowledgements

This work was supported by the European Union and the European Social Fund through the EFOP–3.6.1–16–2016–00022 project and by the Higher Education Institutional ExcellenceProgram (NKFIH-1150-6/2019) of the Ministry of Innovation and Technology in Hungary, within the framework of the Biotechnology thematic program of the University of Debrecen.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

István Pócsi http://orcid.org/0000-0003-2692-6453

Additional information

Funding

This work was supported by the Higher Education Institutional Excellence Program (NKFIH-1150-6/2019) of the Ministry of Innovation and Technology in Hungary, within the framework of the Biotechnology Thematic Program of the University of Debrecen.