[Selection of a community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite- containing sulphide ore flotatation concentrate].

A community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite-containing sulphide ore flotation concentrate was selected. The Acidithiobacillus caldus OP-1 and Ferroplasma acidiphilum OP-2 cultures were identified to be dominating members. The presence of the Acidithio- bacillusferrooxidans OP-3, Leptospirillumferriphilum OP-4, and Sulfobacillus thermosulfidooxidans OP-5 cultures in the community's composition was also mentioned. The analysis results of solid residues of the process showed a greater elemental sulfur oxidation level and gold recovery when the initial pH value in tank I was maintained at a level of 1.8-2.0 (90.5%) rather than 1.6-1.8 (86.3%).

[Oxidation of sulfur-containing substrates by aboriginal and experimentally designed microbial communities].

Aboriginal and experimental (constructed of pure microbial cultures) communities of acidophilic chemolithotrophs have been studied. The oxidation of elemental sulfur, sodium thiosulfate, and potassium tetrathionate as sole sources of energy has been monitored. The oxidation rate of the experimental community is higher as compared to the aboriginal community isolated from a flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore. The degree of oxidation of the mentioned S substrates amounts to 17.91, 68.30, and 93.94% for the experimental microbial community and to 10.71, 56.03, and 79.50% for the aboriginal community, respectively. The degree of oxidation of sulfur sulfide forms in the ore flotation concentrate is 59.15% by the aboriginal microbial community and 49.40% by the experimental microbial community. Despite a higher rate of oxidation of S substrates as a sole source of energy by the experimental microbial community, the aboriginal community oxidizes S substrates at a higher rate in the flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore, from which it was isolated. Bacterial-chemical oxidation of the flotation concentrate by the aboriginal microbial community allows for the extraction of an additional 32.3% of gold from sulfide minerals, which is by 5.7% larger compared to the yield obtained by the experimental microbial community.

[Bacterial leaching of manganese ores].

Leaching of various types of ores, containing 12-30% manganese, by the thiobacterium Acidithiobacillus ferrooxidans was studied. Leaching of reduced ores (manganocalcite and manganiferous limestone) was mediated mainly by degradation of manganiferous minerals (by sulfuric acid produced in the course of bacterial oxidation of pyrite or sulfur). Bacterial treatment of the ores for 144 and 192 h allowed solubilization of 96-98% of manganese. Inoculation of bacteria into pulp with pyrite increased the rate of leaching of oxide ore (psilomelane) by 37%, and the degree of its extraction within 180 h increased from 80 to 97%.

[Effect of temperature on the rate of oxidation of pyrrhotite-rich sulfide ore flotation concentrate and the structure of the acidophilic chemolithoautotrophic microbial community].

Oxidation of flotation concentrate of a pyrrhotite-rich sulfide ore by acidophilic chemolithoautotrophic microbial communities at 35, 40, and 45 degrees C was investigated. According to the physicochemical parameters of the liquid phase of the pulp, as well as the results of analysis of the solid residue after biooxidation and cyanidation, the community developed at 40 degrees C exhibited the highest rate of oxidation. The degree of gold recovery at 35, 40, and 45 degrees C was 89.34, 94.59, and 83.25%, respectively. At 40 degrees C, the highest number of microbial cells (6.01 x 10(9) cells/mL) was observed. While temperature had very little effect on the species composition of microbial communities, except for the absence of Leptospirillum ferriphilum at 35 degrees C, the shares of individual species in the communities varied with temperature. Relatively high numbers of Sulfobacillus thermosulfidooxidans, the organism oxidizing iron and elemental sulfur at higher rates than other acidophilic chemolithotrophic species, were observed at 40 degrees C.