Comparison of microbial diversity during column bioleaching of chalcopyrite at different temperatures

Column bioleaching of chalcopyrite was conducted at 33, 45, and 65 °C, and the copper leaching rates after 220 days were 38.50, 51.35, and 56.75%, respectively. In order to compare the microbial diversity at different temperatures, the microbial community structures of both bacteria and archaea in the columns were analyzed using 16S rRNA gene clone library on day 220. Clone library results indicated that although both iron oxidizers and sulfur oxidizers occurred at all temperatures, iron oxidizers were dominant at 33 and 45 °C and sulfur oxidizers were predominant at 65 °C. With regard to bacterial community structure, Leptospirillum ferriphilum was the principal bacterium at 33 and 45 °C, and uncultured sulfur-oxidizing symbiont bacteria were dominant at 65 °C. On the other hand, with regard to archaea, only Ferroplasma sp. was detected at 33 °C, cultures similar to uncultured archaeon clone were dominant at 45 °C, and Metallosphaera sedula was predominant at 65 °C. Thus, it is suggested that different community structures occur at different temperatures, and that thermophilic chalcopyrite bioleaching should be inoculated and operated at high temperature in order to allow thermophiles to become the dominant microorganism in the system.