Background. The formation of an exoelectrogenic biofilm in a microbial fuel cell (MFC) is an important stage, because it affects later on current generation by the system. The fermented residue after methanogenesis as an inoculum contains not only exoelectrogenic microorganisms, but also methanogens, which reduce the productivity of MFC. The use of current allows the formation of a biofilm enriched with exoelectrogenic microorganisms. Objective. The purpose of our study was to establish the parameters of MFC under periodic application of external voltage. Methods. A two-chamber H-type MFC with a salt bridge between the chambers was used for the study. The anolyte was stirred with a magnetic stirrer for 4 h a day and a 3V voltage was simultaneously applied to create selective conditions for exoelectrogenic biofilm growth. Results. The application of external voltage stimulated the increase in the current and voltage of the MFC. With the periodic application of an external voltage, the MFC current increased to 788 ± 40 mA for the MFC with a resistor and without load. After disconnection and discharge, the MFC current dropped to 189 ± 10 mA for the MFC without load and to 154 ± 8 mA for the MFC with a resistor, respectively. Under the conditions of MFC operation without applying external voltage, the current was 960 ± 50 mA for MFC with an open circuit and 672 ± 35 mA for MFC with a closed circuit when a resistor is connected. For all MFC, the current gradually decreased over time. MFC demonstrated capacitive behaviour: after accumulating charge for 4 h, a discharge from 622 ± 30 mV to 462 ± 23 mV was observed. Microscopy showed fouling of the anode. Since the fermented residue after methanogenesis is mixed consortium, the anodic biofilm was also mixed consortium enriched with different species of exoelectrogens. Conclusions. Periodic application of external voltage allowed to increase the current by 17% and double the voltage compared to MFC without external voltage supply. However, after disconnecting the external voltage source, the MFC gradually discharged, that is, the current and voltage decreased. The maximum value of the current of the MFC with an open circuit was 22% more than the MFC with a closed circuit.

Biofuel cells (BFCs) are an environmental friendly technology that can simultaneously perform wastewater treatment and generate electricity. Peculiarities that hinder the widespread introduction of this technology are the need to use artificial aeration and chemical catalysts, which make the technology expensive and cause secondary pollution. A possible solution to this issue is the use of biocathodes with microalgae and cyanobacteria. Microalgae in the biocathodic chamber produce oxygen as the terminal electron acceptor. Various BFC technologies with algal biocathode (microbial fuel cells, microbial desalination cells, and plant microbial fuel cells) can address a variety of issues such as wastewater treatment, desalination, and CO 2 capture. The main technological parameters that influence the performance of the biocathode are light, pH, and temperature. These technological parameters affect photosynthetic production of oxygen and organic compounds by microalgae or cyanobacteria, and hence affect the efficiency of electricity production, wastewater treatment and production of added-value compounds in microalgae biomass like lutein, violaxanthin, astaxanthin. The ability to remove carbon, nitrogen, and phosphorus compounds; antibiotics; and heavy metals by pure cultures of microalgae and cyanobacteria and by mixed cultures with bacteria in the cathode chamber can be used for wastewater treatment.

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The enzyme-linked immunosorbent assay (ELISA) is the most informative and versatile method of serological diagnostics. The possibility of detection by ELISA of specific antibodies of different classes allow one to differentiate primary infectious processes and their remission, exacerbation and chronic disease (holding of differential diagnosis). This approach is implemented in the methodology for evaluation of patients for the presence of humoral immune response against TORCH-infections pathogens (toxoplasmosis, rubella, cytomegalovirus, herpes simplex viruses infections, and some others). Therefore, testing for the presence of specific IgG and IgM antibodies against TORCH-infection pathogens in blood serum is an important element of mother and child protection. The essential problem in the production of IgM-capture ELISA diagnostic kits is obtaining positive control. The classic version of positive control is human blood serum (plasma) containing specific antibodies. But specific IgM-positive sera are insignificant raw material. This fact can significantly limit the production of diagnostic kits, especially in case of large-scale manufacture. We have suggested a methodological approach to the use of synthetic positive controls in IgM-capture ELISA kits based on conjugate of normal human IgM and monoclonal antibodies against horseradish peroxidase. It was found that it is possible to realize such a task by means of NHS ester-maleimide-mediated conjugation (by sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate), reductive amination-mediated conjugation (by sodium periodate) and glutaraldehyde-mediated conjugation. It was found that conjugates of normal human IgM and monoclonal antibodies against horseradish peroxidase obtained using NHS ester-mediated maleimide conjugation and periodate method are homogeneous in molecular weight, whereas conjugate synthesized by glutaraldehyde method comprises at least three types of biopolymers with close molecular weight. It was found that synthetic positive control obtained by different methods are characterized by higher titre compared to IgM-positive high-titre serum. However, positive control obtained by NHS ester-mediated maleimide conjugation has the best titration profile characteristics. We have suggested a methodological approach to the use of synthetic positive controls in indirect ELISA kits based on conjugate of normal human IgM (IgA) and monoclonal antibodies against major outer membrane protein of Ch. trachomatis. It was found that it is possible to realize such task by means of NHS ester-maleimide-mediated conjugation (by sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate) and reductive amination-mediated conjugation (by sodium periodate). It was found that synthetic positive control obtained by different methods are characterized by higher titre compared to IgM- and IgA-positive high-titre serum. However, positive control obtained by NHS ester-mediated maleimide conjugation has the best titration profile characteristics, both at the release time and after a week’s storage at 37 °C.