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The ability of acidophilic microorganisms to oxidize sulfide minerals is increasingly used in biohydrometallurgical technologies to produce non-ferrous and precious metals from sulfide ores. Strains of Acidithiobacillus ferrooxidans and Sulfobacillus thermotolerans often dominate heap bioleaching processes. Due to their high ability to catalyze redox processes, it has been suggested that they can be used in the technology of microbial fuel cells (MFCs). MFC allows using organic and inorganic waste as a substrate for microorganisms, rendering them harmless with parallel generation of electric current. The aim of this work was to study the electrochemical processes that occur in the cathode and anode spaces of MFCs under the action of acidophilic chemolithotrophic microorganisms on sulfur-containing and iron-containing mining wastes. As objects of study, strains of acidophilic chemolithotrophic microorganisms were used: 1) A. ferrooxidans 61, obtained from Dr. Sc. N. Vardanyan, Head of the Laboratory of Geomicrobiology of the Scientific and Production Center “Armbiotechnology” of the National Academy of Sciences of Armenia; the strain was isolated in Tanzut (gold-polymetallic deposit), from acid drainage at ore deposits in the Lori region of Armenia; 2) S. thermotolerans Kr1 isolated from pulp of a gold-bearing sulfide concentrate treated at 40 ° C in a gold mining factory (Siberia). The substrates for microorganisms were molecular sulfur, iron (II) sulfate, and pyrite tailings from one of the mining and processing plants in Russia. Voltammograms were recorded using a potentiostat and «IPC Pro» software. The concentration of ferrous and oxide iron was determined by complexometric titration with trilon B. Using the method of cyclic voltammetry, data were obtained that testify to the intensification of redox processes using these systems. So, when utilizing elemental sulfur by A. ferrooxidans 61 strain, redox signals in the cathode and anode regions were recorded on the polarization curves. During utilization of iron sulfate in the voltammogram, significant peaks were noted in the reduction area. The voltammogram in the presence of the S. thermotolerans Kr1 strain in media with all tested substrates also showed significant redox signals in the field of oxidation and reduction. The intensification of the MFС operation was shown when using S. thermotolerans Kr1 and A. ferrooxidans 61 strains as cathode bioagents in them. The obtained materials suggest the possibility of using this biochemical system as catholyte in biofuel elements to reduce overvoltage at the cathode. [ABSTRACT FROM AUTHOR]

Baikal sponges account for a significant proportion of lake zoobenthos. The filtration activity of sponges determines their important role in the processes of self-purification of a reservoir. In recent years, depression has been observed, and in some areas even the death of the Baikal sponges. It has been suggested that the negative phenomena observed in the sponge populations may be associated with an increase in the supply of various detergents and surfactants to Lake Baikal. The trophic activity of the Baikal sponges is studied very little. In this regard, under laboratory conditions, the filtration activity of the Baikal sponges of the family Lubomirskiidae (Baikalospongia bacillifera (Dybowski, 1880), Lubomirskia baicalensis (Pallas, 1771)) was investigated. Before the start of the experiment, the sponges were adapted in laboratory conditions in aquariums with Baikal water in low light and at a temperature corresponding to the lake. Baikal at the time of collecting material. Yeast cell cultures were used as a food substrate: Yarrowia lipolityca and Saccharomyces cerevisiae, cultures of Scenedesmus quadricauda. The exposure time in the experiments was 24 hours. The concentration of microorganisms was determined by the fluorimetric method (by chlorophyll luminescence), by direct counting in the Goryaev chamber. In all experiments with the addition of sponges, a decrease in the concentration of microorganisms — cells was observed: Y. lipolityca, S. cerevisiae, S. quadricauda. Starting from a certain concentration, sodium dodecyl sulfate - the main component of detergents - inhibited the filtration activity of sponges. It is shown that when using the luminescent method of studying the filtration activity of sponges, the output of their own symbiotic algae cells can significantly distort the results of the experiment. In direct counting in experiments with the use of yeast, large cells of some microorganisms, released from sponges and already present there, can also make a serious mistake. Thus, experiments have shown that the most reliable way to determine the absorption of microorganisms with Lubomirskiidae sponges is to determine the concentration of S. quadricauda cells by direct counting. [ABSTRACT FROM AUTHOR]