Bioleaching of chalcopyrite by UV-induced mutagenized Acidiphilium cryptum and Acidithiobacillus ferrooxidans

The original strains Acidithiobacillus ferrooxidans GF and Acidiphilium cryptum DX1-1 were isolated from the drainage of some caves riched in chalcopyrite in Dexing Mine in Jiangxi Province of China.The optimum temperature and pH for growth were 30℃and 3.5 for Ac.cryptum DX1-1,and 30℃and 2.0 for At.ferrooxidans GF,respectively.For Ac.cryptum DX1-1,the optimum UV radiating time was 60 s and the positive mutation rate was 22.5%.The growth curves show that Ac.cryptum after mutagenesis reached stationary phase within 60 h,which was 20 h earlier than the original strain.For At.ferrooxidans GF,the optimum mutation time was 60 s and the positive mutation rate was 35%.The most active UV-mutated strain At.ferrooxidans GF oxidized all the ferrous after 48 h.The bioleaching experiments showed that bioleaching with the mixture of UV-mutated strains of At.ferrooxidans GF and Ac.cryptum DX1-1(1:1)could extract 3.01 g/L of copper after 30 d,while the extracted copper was 2.63 g/L with the mixture of the original strains before UV-mutation.At the end of the bioleaching experiments,the proportion of the cell density in the cultures of Ac.cryptum DX1-1 and At.ferrooxidans GF was approximately 1:5.