A.Yu. Tyurin-Kuzmin - Ph. D. (Med.), Senior Research Scientist, State scientific center of Russia Federation - Institute of Biomedical Problems of RAS, Moscow E-mail: alturkuz@mail.ru D.V. Korshunov - Junior Research Scientist, State Scientific Center of Russia Federation - Institute of Biomedical Problems of RAS, Moscow E-mail: shinobi83@mail.ru A.V. Punegova - Post-graduate Student, State Scientific Center of Russia Federation - Institute of Biomedical Problems of RAS, Moscow E-mail: chilly_ice@mail.ru Yu. V. Suprunova - Research Scientist, Federal State Budgetary Scientific Institution - All-Russian Research Institute of Agricultural Biotechnology?, Moscow E-mail: julysupr@yandex.ru V.A. Dubovitskaya - Head of Department of bacteriology, Ltd. LMS Clinic, Moscow E-mail: v.dubovitskaya@7828882.ru I.A. Smirnov - Ph. D. (Eng.), Head of the Laboratory, State Scientific Center of Russia Federation - Institute of biomedical problems of RAS, Moscow E-mail: smirnov47@gmail.com V.K. Ilyin - Dr. Sc. (Med.), Professor, Head of Department, State Scientific Center of Russia Federation - Institute of Biomedical Problems of RAS, Moscow E-mail: ilyin@imbp.ru

Microbial fuel cells (MFC) represent an environmentally friendly method of producing electricity using the natural properties of bacterial communities. Test (MFC) during the flight of the satellite «Photon-4m» showed that this process also can proceed in space, in zero gravity state. However, the resulting power of the electric current is small, and it encourages searching for ways to improve the efficiency of (MFC). In natural conditions the decomposition of organic waste is carried out by microbial communities, combined with the redox reactions, i.e. transfer from the decomposition of electrons and protons. Microbial communities were also named the activated sludge (AS). Mature AS consists of floccules - structured system, which contain inside microaerophilic and anaerobic bacteria, and outside - aerobic bacteria. The outer and inner layers are connected with structures engaged in the transportation of the decomposition products of organic substances, including electrons and protons. It is easy to notice that the (MFC) construction is topologically similar to floccule AS. The only difference is that the compound of electrons and protons is carried out with oxygen in the water chamber without microorganisms. The aim of this work was to evaluate the influence of the presence of microorganisms in the water chamber on the productivity of (MFC). The main courses, which influence to the maturation of AS are: 1) the conditions of dynamic resourcing, i.e. the transfer of nutrients and products of their decomposition, as well as mechanical pressure on the AS; 2) the nutritional conditions, i.e., supply of nutrients, an appropriate system functionality processing; 3) not exceeding the threshold of toxic substances, which are almost presented in the sewage. Suggesting a similar course of events, we filled out the microbial and the water-chamber of (MFC) with the identical mixture sludge. Cells (MFC) filled in the standard way controlled them, i.e. the sludge mixture was placed only in the microbial cell. One pair of cells (control-experiment) was still on the laboratory table, and another pair was placed on a shaker with moderate shaking. We used polypropylene cells in the shape of two concentric vessels. The inner was microbial chamber, its volume was 280 ml, and it was closed. Membrane MK-40 (JSC «Shchekinoazot», Russia) was fixed on the bottom of the chamber, its area was 8 cm. And the outer chamber, with a volume of 300 ml, was open at the top for air and played the role of the water chamber. The electrode in the microbial chamber was made of metalized graphite coated with carbon fabric and its area was 62 cm2 (the microstructure of the surface has not been taken into account), the water chamber-s electrode was made of smooth graphite and its area is 20 cm2. Electrodes were connected across a resistance load of 150 kω. Mixture sludge was taken from Moscow Kuryanovskaya water purifying plant. Studies of the microflora of the MFC were carried out by traditional methods. Сulturing was performed in the TSA medium, Wilkins medium and LB agar. The obtained colonies were studied by optical microscopy and, subsequently, were identified to species on the Bruker Daltonik MALDI (Bruker, USA) analyzer. Culture was identifiable if the figure of the colonies, morphology of the cells and data received on an analyzer were matched. Despite immediately after filling «double mixture sludge shaking cell» gave a lower volts, after 26 days it overtook the control cell, and then overtook and began to consistently exceed the «control shaking cell» at 200 mV. «Double mixture sludge non shaking cell» without extra shaking have not caught up the control cell, and remained below at 200 mV. The result of microbiological studies shows that all cultures have some common features of energy metabolism - all detected bacteria are facultative or obligate aerobes. Perhaps, it was the reason why from the cathode chamber, open to air access, more species were allocated. Most species isolated from MFC have an alternative form of existence in anoxic conditions - nitrate respiration. Species like Staphylococcus and Bacillus subtilis piscifermentas, restore nitrogen to ammonia, thus decomposing proteins into peptides and amino acids, which were then utilized by their cells. Another, more numerous group of bacteria was represented by species, that reduce nitrate to nitrite, nitrogen oxides and molecular nitrogen. Four species from seven, discovered in the cathode chamber, were capable for denitrification. Such a predominance of the microflora with an alternative oxygen-free breath can be explained by the competition for oxygen between bacteria and biotope areas with different concentrations of oxygen and substrates with a high content of nitrogenous compounds. It is possible that nitrate respiration is a kind of adaptation to the existence in the MFC. The obtained data approved that (MFC) is similar to AS floccule. Evolution of the microbial community of the mixture sludge in the aerobic and the anaerobic chambers (MFC) apparently leads to two ways to the formation of two different communities that complement each other in the composition of MFC and improve (MFC) due to additional dynamic actions (shaking). Shaking improves the functioning of the microbial community in (MFC). The aerobic community without it cannot be formed. Perhaps this is because sludge prevents the access of oxygen to the electrode. It is obvious that now, in laboratory tests, the shaking takes much more energy than MFC can produce. But in this research, we solved a fundamental problem: if the formation of aerobic sludge population of microorganisms that increase efficiency of (MFC) is possible or not. In practice, likely different technological solutions to increase the ratio of received and expanded energies in the implementation of the described approach are possible.

 

1. Debabov V.G. Proizvodstvo ehlektrichestva mikroorganizmami // Mikrobiologija. 2008. T. 77. № 2. S. 149-157.
2. Logan B.E. Microbial Fuel Cells, WILEY-INTERSCIENCE. 2008. 213 p.
3. Nikitina O.G. Bioehstimacija: kontrol processa biologicheskojj ochistki i samoochishhenija vody. M. 2010. 288 s.
4. Tanasupawat S., Hashimoto Y., Ezaki T., Kozaki M., Komagata K. Staphylococcus piscifermentas sp. nov., from Fermented Fish in Thailand // International Journal of Systematic Bacteriology 1 October 1992. № 42 (4). P. 577-581. doi:10.1099/00207713-42-4-577.
5. Stetina V., Lauková A., Strompfová V., Svec P., Sedlácek I. Identification of Staphylococcus piscifermentans from dog feces // Folia microbiologica. 2005. № 50(6). P. 524-8. doi:10.1007/bf02931442. PMID 16681152.
6. Gusev M.V., Mineeva L.A. Mikrobiologija. M.: Izdatelskijj centr «Akademija». 2003. 464 s.