Tolerance of three fungal species to lithium and cobalt: Implications for bioleaching of spent rechargeable Li‐ion batteries

• Published in: Journal of applied microbiology Vol. 131; no. 2; pp. 743 - 755
• Main Authors: Lobos, A., Harwood, V.J., Scott, K.M., Cunningham, J.A.
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.08.2021
• Subjects: Acid production; Aspergillus niger; Bacterial leaching; Batteries; bioleaching; Biomass; Cobalt; Exposure; Fungi; Heavy metals; Leaching; Lithium; Lithium-ion batteries; Li‐ion battery; metal biorecovery; Metals; Organic acids; Penicillium chrysogenum; Penicillium simplicissimum; Rechargeable batteries; Species; tolerance index; Toxicity; Penicillium simplicissimum; metal biorecovery; Aspergillus niger; Li-ion battery; tolerance index; bioleaching; organic acids; Penicillium chrysogenum
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/jam.14947

Aims This paper aims to quantify the growth and organic acid production of Aspergillus niger, Penicillium chrysogenum and Penicillium simplicissimum when these fungi are exposed to varying levels of lithium (Li) and cobalt (Co). The study also tests whether pre‐exposing the fungi to these metals enables the fungi to develop tolerance to Li or Co. Methods and Results When cultures of A. niger, P. chrysogenum or P. simplicissimum were exposed to 250 mg l–1 of Li or Co, biomass production and excretion of organic acids were significantly inhibited after 5 days of growth compared to cultures grown in the absence of these metals. Pre‐exposing cultures of A. niger to 250 mg l–1 of Li or Co for 20 days significantly increased biomass production when the fungus was subsequently sub‐cultured into 250 or 500 mg l–1 of Li or Co. However, pre‐exposure of P. chrysogenum or P. simplicissimum to 250 mg l–1 of Li or Co for 20 days did not increase biomass production. Conclusions Aspergillus niger, but not the Penicillium species, developed tolerance to Li and to Co during the 20‐day pre‐exposure period. Therefore, processes that utilize fungal bioleaching with A. niger to mobilize and recover valuable metals such as Li or Co should consider a pre‐exposure step for fungi to improve their tolerance to metal toxicity. Significance and Impact of the Study Fungi may have the ability to extract valuable metals such as Li and Co from spent rechargeable batteries. However, the toxicity of the extracted metals can inhibit fungal growth and organic acid production. Pre‐exposure to metals may alleviate toxicity for some fungal species. This knowledge can be used to improve the design of bioleaching protocols, increasing the potential for fungal bioleaching to become an economical and environmentally friendly method of recovering Li and Co from spent batteries.