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

Abstract

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.

Recovery of valuable metals from spent lithium-ion batteries using microbial agents for bioleaching: a review

“…Additionally, biosorption and intracellular bioaccumulation hinder the transport of metal ions into cells. The metal solubilization capacity of microbial agents can be improved by the adaptation method (i.e., enhancement of microbial resistance to toxic metals) by exposing the microbes to the toxic environment initially by gradually increasing spent LIBs pulp density ( Bahaloo-Horeh et al, 2018 ), adding synthetic lithium and cobalt salt solutions ( Lobos et al, 2021 ) or by adding metallic catalysts (Ag + or Cu 2+ ions) ( Zeng et al, 2012 , 2013 ). A few studies have applied microbial consortia (e.g., mixed culture of IOB and SOB) in the bioleaching process ( Heydarian et al, 2018 ; Ghassa et al, 2020 ), and obtained a high metal leaching yield.…”

“…The spent medium-based bioleaching can be applied to the spent LIBs containing diverse toxic components namely metals, electrolytes and organic solvents. Among the three types of bioleaching approaches, the spent medium bioleaching is most preferable since the leaching efficiency is usually higher in spent medium-based bioleaching tests compared to others (one-step or two-step method) ( Horeh et al, 2016 ; Alavi et al, 2021 ; Lobos et al, 2021 ). Since there is no physical contact between microbial agents and spent LIBs particles in spent medium leaching, the individual process (biological and chemical) can be optimized ( Bahaloo-Horeh et al, 2019 ).…”

“…Fungi are the heterotrophic microorganisms which use organic carbon-based materials as the carbon source for their growth and metabolism ( Bahaloo-Horeh et al, 2019 ). Several fungal species namely Aspergillus niger , Aspergillus tubingensis , Penicillium simplicissimum , and Penicillium chrysogenum are employed for the extraction of metals from electronic wastes ( Bahaloo-Horeh et al, 2019 ; Işıldar et al, 2019 ; Lobos et al, 2021 ). However, in spent LIBs bioleaching, A. niger is highly favored due to less complexity in the growth and harvesting process and higher yields ( Roy et al, 2021a ).…”

“…In contrast to bacteria, fungi have the greater capacity for tolerance to diverse toxic metals, having a shorter lag phase and faster leaching rate as well as fungi can grow in both acid- and alkaline-consuming wastes ( Horeh et al, 2016 ). A study compared the metal tolerance capacity of three fungi species namely A. niger (ATCC 6275), P. chrysogenum (ATCC 10108) and P. simplicissimum (ATCC 48705) by exposing them 250 mg/L of CoCl 2 or LiCl solution over a period of 20 days ( Lobos et al, 2021 ). Among the three fungal species, only A. niger developed tolerance to both metals since an increase of biomass production was observed.…”

Potential of bioaugmentation of heavy metal contaminated soils in the Zambian Copperbelt using autochthonous filamentous fungi

“…The methods used by Lobos et al (2020) were employed to determine the tolerance capacity of filamentous fungi. Heavy metals stock solutions were obtained by diluting the metal salts CuSO 4 .5H 2 O, CoCl 2 , FeSO4.7H 2 O, MnCl 2 .6H 2 O, and ZnSO 4 .7H 2 O with distilled water in a conical flask, followed by serial dilutions to obtain 500, 1,000, 2000, and 5,000 ppm concentrations.…”