Microbial population performing biooxidation of flotation concentrate of gold bearing sulfide ore containing pyrite, arsenopyrite, and pyrrhotite was studied using cultural and molecular biological (metagenomics sequencing of V3-V4 fragments of 16S rRNA gene) approaches. The biooxidation of the concentrate was conducted at temperatures from 38 to 42°C. Strains of Acidithiobacillus thiooxidans, Acidiphilium multivorum, Leptospirillum ferriphilum, Sulfobacillus thermotolerans, Ferroplasma acidarmanus, and Ferroplasma acidiphilum were isolated from the samples of the pulp from biooxidation reactors. It was shown that optimum temperatures of isolated strains were from 38 to 40°C. Metagenomic analysis demonstrated predominance of the genera Acidiferrobacter, Acidithiobacillus, Acidiphilum, Leptospirillum, and Ferroplasma. According to results of molecular biological analysis, share of the genus Acidithiobacillus was of 0 to 25%, share of the genus Acidiferrobacter was of 7 to 56%, share of the genus Acidiphilum was of 0.03 to 36%, share of the genus Leptospirillum was of 0.7 to 7%, whereas share of the archaea of the genus Ferroplasma was of 33 to 94%. Thus, it was shown that representatives of the genus Ferroplasma can play significant role in bioleach process. Representatives of the genus Acidiferrobacter were previously detected in acid mine drainages, acid soils as well as in bioleach heaps and reactors, whereas data on predominance of the genus in tank bioleach processes have not been presented in the literature. In the present study, strains of the genus Acidiferrobacter were not isolated despite application of the nutrient media recommended for Acidiferrobacter and their properties were not studied. Nevertheless, results of the present study suggest that representatives of the genus Acidiferrobacter have a great impact on industrial bioleach processes.

No abstract

No abstract

This research work has developed a processing technology for full oxidation of the biocake from gold-arsenic flotation concentrate with high pyrrhotite content by neutrophilic association of microorganisms, which oxidize elemental sulphur and antimony sulphide at a high rate. Biocake, which is produced as a result of oxidizing the sulphides in the flotation concentrate at pH 1,7 – 1,9 by acidophilic bacteria of chemolithotrophic microorganisms and containing around 3%-5% of elemental sulphur, is then fully oxidized by association of neutrophilic bacteria at рН 7,0-8,0.

The search for the methods of detoxication is a key direction in modern ecology and biotechnology. One of the possible ways of detoxication of pollutants may be the use of humic substances-the products of natural transformation of various organic substances. Today, more and more data on the ability of humic substances to decrease the detrimental influence of toxicants appear [1,2]. Earlier, the effect of detoxication was studied using classic test systems, such as fish, algae, crustaceans, and plants [2][3][4][5][6].However, despite the long-term experience of studying the properties of humic substances, the question on the mechanism of the detoxicating effect of humic substances remains open. It was assumed that the detoxicating properties of humic substances are determined by their ability to reduce oxidants. The presence in humic substances of phenolic groups and fragments carrying unpaired electrons allows to assume the possibility of transition (in particular, bivalent mercury) into reduced and, respectively, less toxic forms upon interaction with humic substances [7,8]. It was also assumed that toxicants are bond by humic substances, which prevents penetration of such large aggregates into cells [9].To study the mechanisms of detoxication of toxicants by humic substances in detail, simple test systems (such as luminous bacteria) are especially promising. They have great advantages over the biotests that were used earlier due to high rate of analysis, sensitivity, simplicity, and possibility of instrumental recording of toxicity.This study is devoted to investigation of the mechanism of detoxication of solutions of organic oxidants using humic substances. Quinones-the products of oxidation of the very widely spread organic pollutants, phenols, were chosen as model organic substances. MATERIALS AND METHODSIn this study, we used a series of quinones with different redox characteristics: 1,4-benzoquinone, tetrafluoro-1,4-benzoquinone, methyl-1,4-benzoquinone, tetramethyl-1,4-benzoquinone, and 1,4-naphtoquinone.The toxicity of quinones was assessed using the bioluminescence biotest Microbiosensor 677F [10], which is based on lyophilized luminous bacteria Photobacterium phosphoreum and produced at the Institute of Biophysics, Siberian Division, Russian Academy of Sciences (Krasnoyarsk).The preparation Gumat-80 (OOO Gumat, Irkutsk) was used as a source of humic substances. The concentrations of humic substances inhibiting bioluminescence most by 20% were selected.Measurements were performed with a BLM-8802 bioluminometer (design office Nauka, Krasnoyarks) [11]. The bioluminescence intensity in the control ( I 0 ) was compared with the bioluminescence intensity recorded in the presence of quinones ( I q ) at a concentration C q . The toxicity of quinone solutions was expressed as I q / I 0 . We used the concentrations of quinone at which I q / I 0 = 0.3-0.5.The degree of detoxication of quinone solutions with humic substances was characterized using the detoxication coefficient K = I qh / I q , where I qh is the ma...