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 low-grade 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. Graphical abstract.

中文翻译：

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使用适应的真菌菌株从低品位铝土矿中增强铝的生物回收

丝状真菌已被证明具有从矿物矿石中回收金属的显着能力。然而，由于矿石中存在的各种重金属引发毒性作用，金属回收率降低。目前的研究强调了真菌对金属在较高纸浆密度下的毒性作用的适应性，以增强低品位铝土矿中铝的生物回收。在之前的研究中，由于黑曲霉和简单青霉对重金属的高金属毒性和低耐受性，当铝土矿浆密度从 1% 增加到 10% (w/v) 时，观察到铝溶解急剧下降。这些真菌经过改造以提高这些真菌菌株的重金属耐受性并获得最大的铝溶解。采用一种新方法来适应真菌菌株，该方法使用含有 5% 铝土矿浆密度并辅以糖蜜作为能源的液体生长培养基。收获适应菌株的菌丝体，随后在低成本的燕麦琼脂培养基中培养。进行批量实验以比较直接一步法和直接两步法生物浸出工艺中的铝浸出效率。FE-SEM 分析揭示了铝土矿耐受菌株的直接破坏和腐蚀作用，这是由于营养菌丝体细丝延伸和渗透到铝土矿基质中。生物浸出铝土矿样品的 XRD 分析表明，刚玉和三水铝石等氧化物矿物的含量显着下降。结果表明，在 5% 纸浆密度和糖蜜作为低成本基质存在下生长的适应真菌菌株成功地从低品位铝土矿中生物浸出和溶解了大量的总铝 (≥ 98%)。图形概要。