Synergetic bioleaching of copper sulfides using mixed microorganisms and its community structure succession

Although mixed bacteria are gradually utilized in copper sulfide bioleaching, the synergistic effects and community successions of mixed bacteria are still not well known, leading to an undesirable extraction efficiency of valuable minerals. Thus, the microbial community successions of pure-source bacteria (two types: Fujian bacteria and Henan bacteria) and mixed bacteria at 0 h, 48 h and 108 h of sulfides bioleaching process were explored in this study using 16S rRNA sequencing. The results show that mixed bacteria are more inclined to obtain a higher bacterial concentration and copper extraction rate than pure-source bacteria community, which is caused by positive synergistic effects of mixed bacteria. The peak copper extraction rate of mixed bacteria (73.7%) was obvious higher than Fujian bacteria (65.2%) and Henan bacteria (60.1%). The dominant bacterial species are Thiobacillus ferrooxidans and Thiobacillus thiooxidans whether it is pure or mixed bacteria, but some strains present different that could make extraction efficiency deviated. Mixed bacteria community could be promoted by abundance succession of minority species such as Firmicutes. It is inferred that the Firmicutes in mixed bacteria present an increasing trend that the relative abundance of bacterial species increases continuously from 0.018 (0 h) to 0.223 (108 h). Besides, microbial diversity is positively correlated with extraction efficiency, specifically, the peak species number of mixed bacteria at 108 h (212) is much higher than pure-source bacteria. This finding reveled a potential measure that sulfides bioleaching could be enhanced by synergistic effect of mixed bacteria sampled from different industrial heaps. (C) 2019 Elsevier Ltd. All rights reserved.