Abstract: In the late stage of low-grade chalcopyrite bioleaching,the accumulated Cu²⁺ would inhibit the cell growth of bioleaching microorganisms and affect leaching efficiency,therefore,it is crucial to domesticate the copper tolerance of bioleaching microorganisms. After 6 months copper tolerance domestication of Acidithiobacillus caldus,the key parameters of the original strain and the domesticated strain in the pure culture and bioleaching process under different copper stress（0,1 and 3 g/L Cu²⁺）were analyzed. The highest specific growth rate（μ_max）in pure culture under 3 g/L Cu²⁺ stress increased from 0.21 d^-1（13 d）before domestication to 0.54 d^-1（10 d）. The efficiencies of copper leaching by the domesticated strain in 0,1 and 3 g/L Cu²⁺ leaching system increased by 17.64%,70.93% and 306.09% respectively,compared to the original one. The morphological observation of the leached slag by scanning electron microscopy（SEM）indicated that the degree of corrosion reduced along with the increased copper stress. Under the same stress conditions,the slag from domesticated leaching system presented more potential adsorption sites and obvious corrosion marks. Fourier transform infrared spectroscopy（FTIR）analysis of key functional groups showed that there were more sulfur-containing groups in the slags of domesticated leaching system. X-ray diffraction（XRD）analysis of slag composition implied that these derivatives in iron and sulfur elements such as Fe₃O₄ and FeS in the domesticated bioleaching system were rich. In sum,the domesticated A. caldus has strong resistance to copper stress and maintains a more active biochemical leaching effect in leaching system,which is expected to play a potential advantage in the similar industrial bioleaching process.

Key words: bioleaching, low-grade chalcopyrite, Acidithiobacillus caldus, copper stress