Enhanced bio-recovery of aluminum from low-grade bauxite using adapted fungal strains

Abstract

Filamentous fungi have been proved to have a pronounced capability to recover metals from mineral ores. However, the metal recovery yield is reduced due to toxic effects triggered by various heavy metals present in the ore. The current study highlights the fungal adaptations to the toxic effects of metals at higher pulp densities for the enhanced bio-recovery of aluminum from lowgrade bauxite. In the previous studies, a drastic decrease in the aluminum dissolution was observed when the bauxite pulp density was increased from 1 to 10% (w/v) due to the high metal toxicity and low tolerance of Aspergillus niger and Penicillium simplicissium to heavy metals. These fungi were adapted in order to increase heavy metal tolerance of these fungal strains and also to get maximum Al dissolution. A novel approach was employed for the adaptation of fungal strains using a liquid growth medium containing 5% bauxite pulp density supplemented with molasses as an energy source. The mycelia of adapted strains were harvested and subsequently cultured in a low-cost oat-agar medium. Batch experiments were performed to compare the aluminum leaching efficiencies in the direct one-step and the direct two-step bioleaching processes. FE-SEM analysis revealed the direct destructive and corrosive action by the bauxite-tolerant strains due to the extension and penetration of the vegetative mycelium filaments into the bauxite matrix. XRD analysis of the bioleached bauxite samples showed a considerable decline in oxide minerals such as corundum and gibbsite. Results showed a high amount of total Al (≥ 98%) was successfully bioleached and solubilized from low-grade bauxite by the adapted fungal strains grown in the presence of 5% pulp density and molasses as a low-cost substrate.

Recent Advances in Biosorption of Copper and Cobalt by Filamentous Fungi

“…The diameter of fungal hyphae is between 2 and 10 μm while a fungal mycelium comprises an interconnected network of mm- to cm-long hypha. Due to their vegetative features, filamentous fungi are among the most economical biofriendly biosorbents available today ( Shah et al, 2020 ). Also, fungal biomasses can be easily produced by using cheap growth media.…”

Effects and interactions of metal oxides in microparticle‐enhanced cultivation of filamentous microorganisms

“…All living species need metals in certain concentrations to fulfill metabolic activities such as the production of organic acids, enzymes, and metabolites [ 92 ]. Thus, the presence of soluble metal ions in microbial cultivations can influence cellular processes and gene regulation of microorganisms profoundly [ 57 ].…”

“…These organic acids as well as amino acids and other metabolites, for example, siderophores, are proven metal leaching agents owing to their capability to form chelates or complexes with metal ions. Thereby, ions can be acquired in limited or insoluble environments and the pH of the environment can be decreased, which is also favorable for the leaching process [ 92 ].…”

“…While spores germinate, fungal mycelia can degrade particle textures through the physical destruction force caused by hyphal extension; releasing a new nutrient source [ 103 , 107 ]. Depending on the cultivated strain and the substrate, metals such as iron, sodium, chlorine, potassium, and calcium leached from the particles, whereas elements such as oxygen, magnesium, aluminum, silicon, and phosphorous persisted [ 92 , 104 ]. It was shown that free aluminum ions were actively accumulated or passively immobilized onto cell walls via biosorption in Streptomyces [ 108 ].…”

Use of Heat-killed Aspergillus ochraceus NRRL 3174 Discs as Biosorbent for petroleum Removal

“…Filamentous fungi, which are ubiquitous in the environment, are among the most economical and bio-friendly biosorbents due to their vegetative properties. They also have advantages such as large-scale biomass production, low cost, and high production capacity when compared to other microorganisms (25,26). Previous studies have been reported that different Aspergillus species as A. niger, A. flavus, A. versicolor, and A. tamarii NRC3 were potently used in biosorption processes (25,27).…”