Effect of Leptospirillum ferriphilum on Acidophile Consortium Biofilm Formation and Chalcopyrite Bioleaching

Cell attachment and biofilm formation are important factors in improving the efficiency of copper extraction from chalcopyrite through biomining methodologies, an important biotechnology for the recovery of metals from sulfidic ores. Acidophilic microorganisms, such as Acidithiobacillus species and Leptospirillum ferriphilum , as “primary colonizers” are key facilitators in promoting microbial attachment to ore particles. This study focused on evaluating the effect of L. ferriphilum on chalcopyrite bioleaching experiments alongside a microbial consortium composed of Ferroplasma acidiphilum , Sulfobacillus thermosulfidooxidans , and Fervidacidithiobacillus caldus . Using epifluorescence microscopy and computational analysis, biofilm formation and its evolution on chalcopyrite and pyrite by the consortium was examined. The results revealed a positive effect of L. ferriphilum on the bioleaching of the chalcopyrite concentrate with a 4% improvement in copper recovery over 38 days. However, it did not improve the adhesion of the consortium’s cells to the ore. Colonization was only detected in the initial 7 days, with a higher colonization in the absence of L. ferriphilum . Experiments with only the consortium (i.e., without L. ferriphilum ) revealed cooperative bioleaching followed by a noncontact mechanism, maintaining a steady cell density in the planktonic phase until the end of the experiment. The results of this study provided new evidence on the importance of the cooperative mechanism whereby microbial cells in both the planktonic and biofilm phases combine their metabolic processes during chalcopyrite bioleaching.