Biorecovery of cobalt and nickel using biomass-free culture supernatants from Aspergillus niger

Abstract

In this research, the capabilities of culture supernatants generated by the oxalate-producing fungus Aspergillus niger for the bioprecipitation and biorecovery of cobalt and nickel were investigated, as was the influence of extracellular polymeric substances (EPS) on these processes. The removal of cobalt from solution was >90% for all tested Co concentrations: maximal nickel recovery was >80%. Energy-dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) confirmed the formation of cobalt and nickel oxalate. In a mixture of cobalt and nickel, cobalt oxalate appeared to predominate precipitation and was dependent on the mixture ratios of the two metals. The presence of EPS together with oxalate in solution decreased the recovery of nickel but did not influence the recovery of cobalt. Concentrations of extracellular protein showed a significant decrease after precipitation while no significant difference was found for extracellular polysaccharide concentrations before and after oxalate precipitation. These results showed that extracellular protein rather than extracellular polysaccharide played a more important role in influencing the biorecovery of metal oxalates from solution. Excitation-emission matrix (EEM) fluorescence spectroscopy showed that aromatic protein-like and hydrophobic acid-like substances from the EPS complexed with cobalt but did not for nickel. The humic acid-like substances from the EPS showed a higher affinity for cobalt than for nickel.

Monazite transformation into Ce‐ and La‐containing oxalates by Aspergillus niger

“…After 2 weeks of incubation, the surface pH showed a significant increase, which was the same as the pH trend in the liquid medium experiments. These results are consistent with recent work where similar pH shifts were observed during the bioleaching of laterite using A. niger grown in liquid media (Yang et al, 2019a). It is known that external medium pH can sometimes increase during incubation of A. niger on mineral-containing solid media and especially when nitrate is supplied as the inorganic nitrogen source (Sayer and Gadd, 1997;Ceci et al, 2015a;Ceci et al, 2015b).…”

“…These results are consistent with recent work where similar pH shifts were observed during the bioleaching of laterite using A . niger grown in liquid media (Yang et al ., ). It is known that external medium pH can sometimes increase during incubation of A .…”

“…citric and oxalic acids can play a significant role in the dissolution of insoluble minerals and can be preceded by the formation of soluble metal–ligand complexes before oxalate‐mediated precipitation occurs (Sayer and Gadd, ). Despite the involvement of organic acids, the bioleaching ability remained at a low level, which was in agreement with another study which found that other phosphate‐solubilizing microbes showed quite a low efficiency in leaching Ce and La from monazite ores ranging from only 0.005% to 0.13% recovery (Shin et al ., ) and also that direct rather than indirect contact may be essential for more efficient fungal bioleaching of elements from ores (Yang et al ., ).…”

“…Aspergillus niger is a ubiquitous environmental fungus known for many industrial applications including citric acid production (Jernejc et al, 1982). It also possesses significant biogeochemical properties that enable interactions with metals and minerals such as mineral dissolution and biologically-induced mineralization (BIM), both of which can be mediated by the extracellular excretion of organic acids (Gadd, 2010;Li et al, 2014;Yang et al, 2019a;Yang et al, 2019b). Aspergillus niger is an efficient producer of oxalic acid (H 2 C 2 O 4 ), which can play a critical role in the BIM process for the bioprecipitation of a number of metals from soluble and insoluble sources .…”

Fungal transformation of selenium and tellurium located in a volcanogenic sulfide deposit

“…For example, the wood-rotting basidiomycete Schizophyllum commune can bioweather black slate through hyphal mechanical pressure and biochemical mechanisms such as siderophore, laccase and organic acid excretion (Kirtzel et al, 2020). Aspergillus niger can mediate direct and indirect bioleaching of cobalt from low grade laterite and pyritic ores (Yang et al, 2019(Yang et al, , 2020. Fungal bioweathering, involving both mineral dissolution and biomineralization mechanisms, has also been demonstrated for silicate and sulfide ores (Wei et al, 2012a(Wei et al, , 2013, manganese oxides including birnessite (Wei et al, 2012b), mimetite (Ceci et al, 2015a), and vanadinite (Ceci et al, 2015b).…”