Comparison of Indigenous and Exogenous Mesophilic Bacteria for the Bioleaching of Low Grade Copper Ores

Using indigenous microorganisms in biomining processes assures few ecological distortions and less time consumption for adaptation. However, there is a debate as to whether an indigenous microbial community is more efficient than one composed of microbial strains selected for specific physiological traits. In order to provide thoughtful opinions in such a debate, a cross-comparison of six strains isolated from two different regions: Chambishi Copper Mine (Zambia) and Dexing Copper Mine (China), was conducted. Physiological properties and leaching performances of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferriphilum in pure and mixed culture were studied. The results showed that strains within species presented similar traits while copper resistance was not species-specific. In terms of leaching efficiency, native strains always achieved higher cell density and greater iron and copper extraction rates than the exogenous. In addition, microbial community analysis revealed the different mixed culture shared almost the same profile, and At. ferrooxidans strains always outcompeted the other strains.