Effect of Different Solvent Extractants on the Activity and Community Structure of Acidophilic Microorganisms

The effect of solvent extractants, such as M5774, Cyanex 272, P204, P507 and N235, on the activity and community structure of acidophilic microorganisms were tested. Cobalt extractant Cyanex 272 did not show much inhibition effect on the growth of acidophiles, while iron extractant N235 had great inhibition effect. When the culture solution contacted with iron extractant P204, nickel extractant P507 and copper extractant M5774, the inhibition effect increased gradually. 16S rRNA gene clone library were used to analyze the initial and extractant contacted final microbial community structure. The initial inoculation microbial populations were mainly composed by Leptospirillum ferriphilum and Acidithiobacillus ferrooxidans. After cultivated in solution containing extractant M5774, Cyanex 272, P204 and P507, the number of the two species decreased, while heterophilic Acidiphilium cryptum became the dominant population. When cultured by M5774 and Cyanex 272, the proportion of Acidithiobacillus ferrooxidans was higher than Leptospirillum ferriphilum, while when cultivated by P204 and P507, the number of Leptospirillum ferriphilum was higher.

Reductive Dissolution of Iron Oxides and Manganese Bioleaching by Acidiphilium cryptum JF-5

In the development of new processes to use the potential of iron reducing bacteria,Acidiphilium cryptum, the main bacteria involved in the reduction of Fe (III) compounds in acidic environments, could play an important biohydrometallurgical role. Thus, the bioleaching of hematite, goethite and a low-grade manganese ore was assayed, in vials and columns, using three different media; two of which included a ligand, oxalate, or a redox mediator, thionine.Although the presence ofA. cryptumwas essential for promoting the dissolution of both iron oxides and the bioleaching of manganese ore, the addition of oxalate to the media tripled and quadrupled the microbial dissolution of hematite and goethite, respectively. Oxalate also had a positive effect in assays performed in columns, however, the addition of thionine to the medium allowed to reach significant hematite dissolution.

Influence of Calcium Nitrate on Microbial Community Structure of Acidophilic Microorganisms

The influence of different concentrations of calcium nitrate on the growth and activity of acidophilic microorganisms were studied and the microbial community structures were compared by 16S rRNA gene clone library analysis. The addition of Ca (NO3)2has a certain effect on the solution potential, and that the time needed to reach the steady potential were prolonged with the increase of Ca (NO3)2concentration but not obvious when it was above 1.64 g.L-1. It also can be observed that the cell numbers decreased with the increase of Ca (NO3)2concentration which can alter the cell osmolarity, and that the time entering the stationary phase of cell concentration was delayed with the addtion of Ca (NO3)2. With the addition of 0.41g.L-1Ca (NO3)2, the percentage ofLeptospirillum ferriphilumandAcidiphilium cryptumdidn’t have great changes, while the unculturedSulfobacillus sp.,Acidithiobacillus ferrooxidansandAlicyclobacillus toleranswere also detected. With the addition of 2.05 g.L-1Ca (NO3)2or more, theAcidithiobacillus ferrooxidansbecome the dominant bacterium (which accounted for more than 90%).