Bacterial community structure change during pyrite bioleaching process: Effect of pH and aeration

A culture-independent approach based on 16S rRNA gene clone library was used to analyze the bacterial community change during the bioleaching of pyrite. In this paper we summarize results from monitoring aerated and periodically aerated pyrite bioleaching conducted in two 3 L stirred reactors at 30 °C. Phylogenetic analyses of 16S rRNA fragments revealed that the retrieved sequences mainly related to genus Leptospirillum, genus Sulfobacillus and genus Acidithiobacillus. The remaining sequences were clustered together with genus Afipia and genus Sporacetigenium. The dynamics of phylogenetic microbial groups' change of the bioleaching processes were investigated and correlated with chemical and physical parameters in the reactors. In both aerated and periodically aerated bioleaching tests, bacteria diversity was decreased at the end. Genus Leptospirillum accounted for a high proportion when the pH was decreased from 1.6 to 1.3 and from 1.0 to 0.9, while the proportion of sequences belonging to genus Sulfobacillus increased when the pH was decreased from 1.3 to 1.0 and below pH 0.9. Under non-aerated condition, Sulfobacillus may have better growth. These results may be used to facilitate the selective depression of pyrite during copper bioleaching and improve commercial plant operation.