Papers by Keyword: Acidophilic Bacteria

Abstract: Chloride leaching is considered a promising alternative method to recover copper from chalcopyrite and other primary copper sulfides, because it favors the leaching kinetics and avoids passivation of minerals. Nevertheless, chloride ions are highly toxic for iron-oxidizing microorganisms that participate in the bioleaching process. A comparative genomic analysis was carried out based on the complete genomes of bacteria belonging to Nitrospirae, Firmicutes, Actinobacteria and Proteobacteria phyla, and of archaea belonging to Euryarchaeota and Crenarchaeota was carried out to identify molecular determinants involved in chloride tolerance of acidophilic iron-oxidizing microorganisms. The results obtained showed that representative Nitrospirae and Firmicutes harbor genes for the biosynthesis and uptake of compatible solutes such as ectoine, trehalose and potassium, which have been shown to have a role in salt tolerance. Microorganisms belonging to other phyla harbor genes for potassium transporters, but no genes for compatible solutes were detected. In agreement with the bioinformatic results, minimum inhibitory concentration (MIC) determinations and growth kinetics experiments showed that Leptospirillum ferriphilum (Nitrospirae) was more tolerant to NaCl than Acidithiobacillus ferrooxidans (Proteobacteria). Furthermore, it was observed that the addition of 0.5 mM ectoine to the L. ferriphilum culture stimulated growth in the presence of 100 mM NaCl. On the contrary, ectoine had no effect on the growth of At. ferrooxidans. These results suggest that ectoine and likely trehalose could play a key role in chloride tolerance in L. ferriphilum. conferring adaptative advantages compared to A. ferrooxidans and possibly other iron-oxidizing microorganisms.

Abstract: Bioleaching experiments of phosphorus from low grade fluorapatite ore containing 8.2% P₂O₅ and from fluorapatite concentrate containing 29.8% P₂O₅ were carried out in shake flasks. Elemental sulphur was supplemented as an energy source for acid generation. Mixed and pure acidophilic bacterial cultures consisting of iron-and/or sulphur-oxidizing bacteria Acidithiobacillus ferrooxidans, A. thiooxidans and Leptospirillum ferrooxidans were used in the experiments. These acidophiles are commonly used in bioleaching of sulphide minerals, but their application on phosphorus bioleaching has been limited. Phosphorus leaching was shown to be a pH-dependant phenomenon. Phosphorus leaching yields of up to 97% and 28% were obtained in 3 weeks for low grade fluorapatite ore and concentrate, respectively. These results indicate a potential for applying bioleaching for phosphorus extraction from low grade materials.

Abstract: The capacity of a microbiological mine water treatment plant may to be enhanced by understanding the microbiological processes. Therefore different samples from the pilot plant were analyzed by culture-independent and cultivation methods. Dominant bacteria could be isolated on overlay plates or enriched in gradient cultures. To immobilize biomass in the pilot plant, various carrier materials were tested. Sessil, the material currently used in the pilot plant, was the most favored and appropriate material.