| The purpose of the paper was to enlarge the knowledge on mineral bioleaching and the effect of L-cysteine on the metal sulphide bioleaching with extreme thermophile. In this paper, the effect of L-cysteine on the surface properties of Ni-Cu sulphide and the bioleaching of Ni-Cu sulphide and chalcopyrite with extreme thermophiles was studied. In addition, the microbial diversity in the bioleaching process was investigated by DGGE-PCR method.The Zeta potentials and IR absorption spectra of Ni-Cu sulfide before and after treated with L-cysteine indicate that L-cysteine adsorbed on Ni-Cu sulfide surfaces through amido, carboxyl and-HS groups. And L-cysteine will change the Zeta potential of Ni-Cu sulfide sulfide. L-cysteine can speed up the bioleaching of Ni-Cu sulphide by A.manzaensis and increase the leaching rate. When the concentration of Ni-Cu sulphide was 2%,0.2g/L of L-cysteine contributed most on the bioleaching of Ni-Cu sulphide. Excess L-cysteine would inhibit the Ni-Cu bioleaching.L-cysteine can also improve the bioleaching rate of Ni-Cu sulfide and chalcopyrite with A.manzaensis, A.brierleyi, M. sedula, S. metallicus. And L-cysteine can affect the microbial community composition during the bioleaching process. In the bioleaching system of Ni-Cu sulfide without L-cysteine, it was dominated by M. sedula, S. metallicus at early bioleaching stage. At the late bioleaching stage, the proportion of A.manzaensis increased, and it was dominated by S. metallicus and A.manzaensis. Only a small portion of A.brierleyi was detected during the whole leaching process. While in the system with L-cysteine added, the system was dominated by A.manzaensis, M. sedula, S. metallicu at the initial stage, with only a small amount of A.brierleyi found. At the late stage, the microorganisms were mainly A.manzaensis and S. metallicus, with only a small portion of M. sedula and A.brierleyi.In the system without L-cysteine, S. metallicus and A.manzaensis played a leading role during the bioleaching process of chalcopyrite with A.manzaensis,A.brierleyi,M. sedula and S. metallicus. The population of M. sedula was small during the leaching process and increased a little at late stage. The microbial community composition in the chalcopyrite leaching system is relatively stable when L-cysteine added. A.manzaensis played a key role in the leaching process with L-cysteine. Since the fourth day the proportion of A.manzaensis in the system has reached 50%, and achieved 67.2% in the end. The proportion of M. sedula in the system always maintained between 16% and 36%, while the proportion of S. metallicus in the system maintained between 10% and 25%. |
