Abstract Considering the environmental issues of cyanide ion, cyanogenic bacteria which are capable of cyanide genesis may be regarded as a potential alternative to conventional cyanidation. The capacities of two cyanogenic bacterial strains namely Pseudomonas aeruginosa and Bacillus megaterium for the cyanide production and gold bioleaching from the pure gold particles and an oxidized gold-bearing ore (6.2 g/ton) were compared. Also, in order to maximize the cyanide bio-production and subsequently the gold recovery, the influences of the initial pH, glycine, FeSO4, NaH2PO4, and MgSO4 concentrations in the growth media were studied and optimized. In the optimal culture condition, P. aeruginosa and B. megaterium produced 66.35 and 67.05 mg/l cyanide, respectively, and 2.5 g/l glycine remained unconsumed. Therefore, bioleaching experiments were performed under the synergistic effect of the cyanide-glycine mixture through the active and passive approaches that the latter averagely improved the Au dissolution by 8%. The concentration of Au in the leachate of B. megaterium was higher in comparison with the other bacterium, and reached 205 and 32.2 μg/l for the pure gold and the original ore, respectively. Moreover, performing a pretreatment stage to remove metal contents before cyanidation, increased the final Au concentration to 44.4 μg/l. Finally, raising the bioleaching pH to 10 increased the Au concentration to 56.8 μg/l which represents >80% gold recovery. Although the Au extraction efficiencies of both strains were low, the observed improvements due to the ferrous and magnesium addition, copper removal, and pH increase are promising for the future works.

中文翻译：

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在残留甘氨酸存在下从氧化铜金矿中提取金的巨大芽孢杆菌和铜绿假单胞菌的生物氰化潜力的比较和优化

摘要 考虑到氰化物离子的环境问题，能够产生氰化物的生氰菌可被视为常规氰化的潜在替代品。比较了两种生氰细菌菌株，即铜绿假单胞菌和巨大芽孢杆菌从纯金颗粒和氧化含金矿石（6.2 克/吨）中产生氰化物和生物浸出金的能力。此外，为了最大限度地提高氰化物生物产量和随后的金回收率，研究并优化了生长培养基中初始 pH、甘氨酸、FeSO4、NaH2PO4 和 MgSO4 浓度的影响。在最佳培养条件下，铜绿假单胞菌和巨大芽孢杆菌分别产生 66.35 和 67.05 mg/l 氰化物，2.5 g/l 甘氨酸未被消耗。所以，在氰化物-甘氨酸混合物的协同作用下通过主动和被动方法进行生物浸出实验，后者平均将Au溶解提高了8％。巨大芽孢杆菌浸出液中金的浓度高于其他细菌，纯金和原矿分别达到 205 和 32.2 μg/l。此外，在氰化之前进行预处理阶段去除金属含量，将最终金浓度增加到 44.4 μg/l。最后，将生物浸出 pH 值提高到 10，金浓度增加到 56.8 μg/l，这表示金回收率超过 80%。尽管两种菌株的金提取效率都很低，但由于添加亚铁和镁、去除铜、