The capacity of sulfur-reducing bacteria Desulfuromonas acetoxidans Geobacter sp. CB35 and Desulfuromusa sp. CB30 and green photosynthesizing bacteria Chlorobium limicola their growth in wastewater of industrial and municipal origin. The strains of exoelectrogens, which are characterized by resistance to heavy metal ions, were isolated from the man-made Yavorivske lake located in the Lviv Oblast in Ukraine (D. acetoxidans Ch. limicola Geobacter sp. CB 30 and Desulfuromusa sp. CB 35). Bacteria D. acetoxidans fuel cell (MFC) with the application of D. acetoxidans W/m 2 and the reduction of chemical oxygen demand of wastewater was 99%. The new approach to improving the MFC performance was investigated. It includes a combination of phototrophic microorganisms Ch. limicola and heterotrophic microorganisms, which reduce the content of nitrates, nitrites, ammonia, sulfates, sulfites, hydrogen sulfide, while simultaneously generating electric current.
To investigate the changes of fatty acid composition of green sulphur bacteria Chlorobium limicola ІМV К-8 cells at the influence of copper (II) sulfate. Methods. Microbiological, biochemical, biometrical. Results. The increase of content of long chain saturated fatty acids of C. limicola ІМV К-8 cells, in particular pentadecanoic, hexadecanoic, heptadecanoic and octadecanoic acids was observed under the influence of copper (II) sulfate in concentrations which caused decrease of biomass accumulation up to 70 %. Among the first reactions of adaptation of C. limicola ІМV К-8 cells under these conditions are cis/trans isomerisation of monounsaturated fatty acids and synthesis of cyclopropane fatty acids. Maintenance of appropriate level of membrane fluidity is provided by branched chain fatty acids. Conclusions. Under the influence of copper (II) sulfate on C. limicola ІМV К-8 cells fatty acids composition of membranes is changed, which causes the increase of membranes fluidity, and, probably, is contributed to more efficient efflux of Cu 2+ ions.
Desulfuromonas acetoxidans IMV B-7384 is exoelectrogenic obligate anaerobic sulfur-reducing bacterium. Its one of the first described electrogenic bacterium that performs complete oxidation of an organic substrate with electron transfer directly to the electrode in microbial fuel cell (MFC). This bacterium is very promising for MFC development because of inexpensive cultivation medium, high survival rate and selective resistance to various heavy metal ions. The size of D. acetoxidans IMV B-7384 cells is comparatively small (0.4-0.8×1-2 μm) that is highly beneficial while application of porous anode material because of complete bacterial cover of an electrode area with further significant improvement of the effectiveness of its usage. The interconnection between functioning of reductive stage of tricarboxylic acid (TCA) cycle under anaerobic conditions, and MFC performance was established. Malic, pyruvic, fumaric and succinic acids in concentration 42 mM were separately added into the anode chamber of MFC as the redox agents. Application of malic acid caused the most stabile and the highest power generation in comparison with other investigated organic acids. Its maximum equaled 10.07±0.17mW/m 2 on 136 hour of bacterial cultivation. Under addition of pyruvic, succinic and fumaric acids into the anode chamber of MFC the maximal power values equaled 5.80±0.25 mW/m 2 ; 3.2±0.11 mW/m 2 , and 2.14±0.19 mW/m 2 respectively on 40, 56 and 32 hour of bacterial cultivation. Hence the malic acid conversion via reductive stage of TCA cycle is shown to be the most efficient process in terms of electricity generation by D. acetoxidans IMV B-7384 in MFC under anaerobic conditions.
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