Identification of the dominant bacterium of two-stage biooxidation of gold-arsenic concentrate

In the process of biooxidation at 39°C in a continuous mode of the gold-arsenic concentrate from the Olympiadinskoe deposit, which was pretreated by chemical leaching with ferric ions, by a microbial association from the BIO department reactors of the Polyus gold mining company, a bacterial culture designated as strain HT-4 was isolated. The bacterium was a spore-forming rod 0.5–0.6 × 1.4–2.0 μm with a flagellum. The optimal temperature for growth and Fe²⁺ oxidation was 55°C. The strain grew in the pH range from 1.21 to 2.10 with the optimum at pH 1.6. The organism was incapable of lithotrophic and organotrophic growth. It grew mixotrophically by Fe²⁺ oxidation in the presence of 0.02% yeast extract. The DNA G+C base content was 48.6 mol %. Based on comparative phylogenetic analysis of 1472-bp nucleotide sequences of 16S rRNA genes, strain HT-4 was classified as Sulfobacillus thermosulfidooxidans. Analysis by pulse-field gel electrophoresis revealed a unique profile of the NotI fragments of the chromosomal DNA. These results demonstrate the strain and species diversity of sulfobacilli in microbial associations involved in biooxidation of concentrates in different technological conditions. The strain “S. olympiadicus S-5” dominated in the process of biooxidation of original concentrate not treated with ferric iron, while S. thermosulfidooxidans HT-4 was predominant in biooxidation of the chemically leached concentrate.     

Bioregeneration of Leaching Solutions during Two-Step Processing of Copper-Zinc Concentrate

A comparative study of the oxidation of ferrous iron ions by various cultures of acidophilic chemolithotrophic microorganisms in solutions obtained after ferric leaching of copper-zinc concentrate at 80°C has been carried out. It was shown that the use of a moderately thermophilic culture for bioregeneration of leaching solutions was preferable. At the same time, the oxidation rate of Fe²⁺ ions reached 0.88 g/(L h), or 21.1 g/(L day). We propose that the activity of the moderately thermophilic culture was due to the presence of the mixotrophic bacteria Sulfobacillus spp., which used organic products of the microbial lysis for their growth. These products were formed during high-temperature ferric leaching of the copper-zinc concentrate with the biosolution.     

The effects of bioleaching conditions on the nonferrous metals content in copper-zinc concentrate

The effects of pH and ferrous iron concentration in cultural medium on the bioleaching of copper-zinc concentrate by mesophilic and moderately thermophilic acidophilic microorganisms were studied. It was revealed that the optimum pH for bioleaching in presence of 5 g/L of ferrous iron was 1.4–1.5. It was shown that bioleaching under optimal conditions led to an increase in the copper content in solid phase from 10.1 to 14% and a decrease in the zinc content from 7.4 to 1.4%. The results of the present work demonstrate that acidophilic microorganisms can be used for treatment of complex sulfide concentrates containing copper and zinc.     

Aggregation of erythrocytes and their membranes flexibility in patients with cancer-associated anemia: Mechanisms of changes under the influence of epoetin alfa

The relationships between the red blood cell (RBC) membrane elasticity and RBC aggregation in healthy individuals and in patients with anemia of malignant tumors treated with human erythropoietin drug epoetin alfa (EA) were analyzed. It was found that prior to the treatment of patients, incubation of RBCs with EA was accompanied by an increase of RBC deformability and the reduction of their aggregation (RBCA). In these circumstances the two characteristics of the RBC microrheology correlated negatively with each other (r =–0.734, p < 0.05). In contrast, aggregation and deformability of RBCs from healthy individuals increased under the influence of EA and positively correlated with each other (r = 0.580, p < 0.05). After a 4-week treatment of patients with EA, aggregation response of the patients’ RBCs was increased by 29% (p < 0.05) and was close to that of healthy RBCs. This change of the RBC aggregation response may be connected with an alteration of the sensitivity of the membrane cationic channel to EA and an increase of the cell deformability. This possibility was supported by experiments with the use of Ca²⁺-channel blocker verapamil and Ca²⁺-chelating agent EDTA. Under these conditions a decrease of the RBC aggregation varied from 40 to 50% (p < 0.05). It was suggested that the effectors of calcium regulatory cascade upon exposure to EA may be membrane integrin receptors of type IIb–IIIa. This assumption was confirmed by experiments employing the inhibitors of these receptors (tirofibam and integrelin) and a preparation of monoclonal antibodies against IIb–IIIa receptors (monafram), which produced a significant decrease (20–30%, p < 0.05) of the RBC aggregation. Thus, our findings suggest that the altered aggregation response of RBCs in anemic patients with malignant tumors can be restored by the correction of anemia with epoetin alfa.     

The role of red blood cell adenylyl cyclase activation in changes of erythrocyte membrane microrheological properties

The ability of red blood cells (RBCs) for the reversible change of their shape under passing through capillaries in microcirculation mainly depends on membrane elasticity of these cells. Phosphorylation of some membrane proteins can result in the changes of microrheological red blood cell properties. Here we show a significant increase in RBC deformability (RBCD) after incubation with isoproterenol (10⁻⁶ M). Red blood cell aggregation (RBCA) decreased under these conditions only slightly. When forskolin (10 μM), an adenylyl cyclase (AC) stimulator, was added to the RBC suspension, RBCD increased significantly (p < 0.05). Some more changes of deformability were found after incubation of RBC with stable penetrating analog of cyclic adenosine phosphate (cAMP), dibutyryl-cAMP, (dB-cAMP, 50 μM) and after phosphodiesterase (PDE) activity inhibition with Vinpocetine, Rolipram, or IBMX. It was found that Gs-proteins inhibitor Clonidine and specific Gi-protein stimulator Mastaparan 7 increased both RBCD and RBCA. On the whole, the data clearly show that the RBC aggregation and deformation changes are related with activation of the different intracellular signaling pathways. We suppose that RBCD increase was mainly associated with activation of the adenylyl-cyclase-cAMP system.     

Leaching of nonferrous metals from copper converter slag with application of acidophilic microorganisms

The leaching process of copper and zinc from copper converter slag with ferric iron in sulfuric acid solutions obtained using the association of acidophilic chemolithotrophic microorganisms was investigated. The best parameters of chemical leaching (temperature 70°C, an initial concentration of ferric iron in the leaching solution of 10.1 g/L, and a solid phase content in the pulp of 10%) were selected. Carrying out the process under these parameters resulted in the recovery of 89.4% of copper and 39.3% of zinc into the solution. The possibility of the bioregeneration of ferric iron in the solution obtained after the chemical leaching of slag by iron-oxidizing acidophilic chemolithotrophic microorganisms without inhibiting their activity was demonstrated.     

Chemical leaching of copper-zinc concentrate with ferric iron biosolution

The process of leaching of copper-zinc concentrate with a solution containing biogenic iron, which is a product of the metabolism of iron-oxidizing microorganisms, was studied. The dependence of leaching rate of metals on temperature and pH was determined. It was shown that up to 98% of zinc and 70% of iron could be removed from the concentrate, while up to 7 and 4 g/L of zinc and copper, respectively, were accumulated in the liquid phase, which was sufficient for metal recovery. It was established that a copper concentrate with copper content up to 16% and only 0.5% of zinc could be obtained after chemical leaching for 340 min at 80°C.     

Role of protein kinases of human red cell membrane in deformability and aggregation changes

The proteomic analysis has shown that the red cell membrane contains several kinases and phosphatases. Therefore the aim of this study was to investigate the role of protein kinases of human red cell membrane in deformability and aggregation alterations. The exposure of red blood cells (RBCs) to some chemical compounds has led to a change in the RBC microrheological properties. When forskolin (10 μM), an adenylyl cyclase (AC) and a protein kinase A (PKA) stimulator were added to RBC suspension, the RBC deformability (RBCD) was increased by 20% (p<0.05). Somewhat more significant deformability rise appeared after RBC incubation with dB-AMP (by 26%; p<0.01). The red cell aggregation (RBCA) was significantly decreased under these conditions (p<0.01). Markedly less changes of deformability were found after RBC incubation with protein kinase stimulator C (PKC)—phorbol 12-myristate 13-acetate (PMA). This drug reduced the red cell aggregation only slightly. The red cell tyrosine phosphotase activity was changed by N-vanadat and a significant RBCD rise and RBCA lowering were obtained. The similar effect was found when the cells were incubated with cisplatin as a tyrosine protein kinase (TPK) activator. It is important to note that a selective TPK inhibitor—lavendustin eliminated the above mentioned effects.     

Biohydrometallurgical technology of copper recovery from a complex copper concentrate

Leaching of sulfide-oxidized copper concentrate of the Udokan deposit ore with a copper content of 37.4% was studied. In the course of treatment in a sulfuric acid solution with pH 1.2, a copper leaching rate was 6.9 g/kg h for 22 hours, which allowed extraction of 40.6% of copper. At subsequent chemical leaching at 80°C during 7 hours with a solution of ferric sulfate obtained after biooxidation by an association of micro-organisms, the rate of copper recovery was 52.7 g/kg h. The total copper recovery was 94.5% (over 29 hours). Regeneration of the Fe³⁺ ions was carried out by an association of moderately thermophilic microorganisms, including bacteria of genus Sulfobacillus and archaea Ferroplasma acidiphilum, at 1.0 g/L h at 40°C in the presence of 3% solids obtained by chemical leaching of copper concentrate. A flowsheet scheme of a complex copper concentrate process with the use of bacterial-chemical leaching is proposed.     

Selective leaching of zinc from copper-zinc concentrate

Biooxidation of copper-zinc concentrate with the use of consortia of mesophilic and moderately thermophilic acidophilic chemolithotrophic microorganisms was studied. Pyrrhotite, sphalerite, and chalcopyrite were the main sulfide minerals of the concentrate. The possibility in principal of complete selective leaching of zinc from sulfide concentrate coupled with minimal recovery of copper (less than 20%) was demonstrated. Selective leaching of zinc could be caused by galvanic interactions between minerals of the concentrate during the biooxidation. The results can be used as the basis for the development of the technologies for production of grade copper concentrate not containing zinc from sulfide copper-zinc concentrate obtained from refractory ores.