A novel conductive composite based on PEDOT:PSS, BSA, and Nafion for effective immobilization of acetic acid bacteria on graphite electrodes as part of biosensors and microbial fuel cells has been proposed. It is shown that individual components in the composite do not have a significant negative effect on the catalytic activity of microorganisms during prolonged contact. The values of heterogeneous electron transport constants in the presence of two types of water-soluble mediators were calculated. The use of the composite as part of a microbial biosensor resulted in an electrode operating for more than 140 days. Additional modification of carbon electrodes with nanomaterial allowed to increase the sensitivity to glucose from 1.48 to 2.81 μA × mM−1 × cm−2 without affecting the affinity of bacterial enzyme complexes to the substrate. Cells in the presented composite, as part of a microbial fuel cell based on electrodes from thermally expanded graphite, retained the ability to generate electricity for more than 120 days using glucose solution as well as vegetable extract solutions as carbon sources. The obtained data expand the understanding of the composition of possible matrices for the immobilization of Gluconobacter bacteria and may be useful in the development of biosensors and biofuel cells.

Bacterial cellulose (BC) produced by the Komagateibacter sucrofermentas VKPM B-11267 bacteria was used as a carrier for immobilization of acetic acid bacteria Gluconobacter oxydans in amperometric biosensors. The bioreceptor was formed on the surface of a screen-printed graphite electrode modified with thermally expanded graphite (TEG) or on the surface of a porous three-dimensional material, nickel foam (NF). Structural features of these materials contributed to the creation of a firm contact between the electrode material and the surface of the BC on which the bacterial cells were immobilized. Scanning electron microscopy showed that bacteria not only sorb on the surface of BC but are also able to penetrate the inner volume of the film. Conductivity of both types of biosensors was studied using impedance spectroscopy and the resistance of the graphite electrode was shown to decrease by three orders of magnitude after its surface is modified with TEG. Bioelectrodes containing BC were used in the construction of an amperometric biosensor for glucose determination. The sensitivity of the biosensor was 3 μA/mM × cm2. Thus, BC in combination with TEG and NF can be used to create three-dimensional electrodes of bioelectrocatalytical devices.

The bioelectrochemical and spectral properties of immobilized Gluconacetobacter sucrofermentas VKPM B-11267 bacteria were studied in the presence and absence of multiwalled carbon nanotubes (MWCNTs). The obtained characteristics were compared with the characteristics of Gluconobacter oxydans , which are phylogenetically close to them and are widely used in bioelectrochemistry. It was shown that modification of the bioelectrode with carbon nanotubes leads to a significant increase in the current level (by 2.5–3 times), as well as to a decrease in the total resistance both in the absence of substrates and in their presence. The potential use of immobilized G. sucrofermentas cells as part of a microbial fuel cell (MFC) was considered. The specific electrical power of an MFC based on immobilized G. sucrofermentas cells was lower than that of an MFC based on G. oxydans cells. Nevertheless, the results obtained indicate that G. sucrofermentas VKPM B-11267 cells can serve as a biocatalyst in MFCs.

The Gluconacetobacter sucrofermentas bacterial cells are immobilized in a chitosan gel on the surface of an electrode obtained by matrix printing. The nature of the change in the bioelectrochemical parameters of the immobilized bacteria under the influence of multiwalled carbon nanotubes (MWCNTs) are studied. We studied the electrochemical signals of cells upon the introduction of substrates (glucose, ethanol) by three methods: chronoamperometry, cyclic voltammetry, and impedance spectroscopy. The introduction of ethyl alcohol at a concentration of 1 mM leads to a decrease in the total resistance of the electrode by a factor of ~40. Modification of the electrode using MWCNTs leads to an increase in the current (by factors of 8 to 10) and an additional decrease in the total electrode resistance by a factor of ~10. These effects are similar to the effects of substrates and MWCNTs on the phylogenetically related Gluconobacter oxydans cells. The formation of bacterial cellulose (BC) membrane cells during the growth does not fundamentally change the effects of the substrates and MWCNTs.

We have investigated the properties of a several bioelectrodes based on the immobilization of Gluconobacter oxydans bacterial cells on carbon superfine materials (CFMs). We use three types of CFMs (as adopted by the working classification CFM 1-3). All bioelectrodes was formed by covering the surface of the CFM via suspension of bacteria in a chitosan gel. The properties of samples are evaluated by measuring the physiological state of the bacteria immobilized: (a) recording the intensity of cellular respiration, (b) for measuring the charge transport characteristics of electrode (bioelectrocatalysis), and (c) by measuring the electrode impedance. Measurements (b) and (c) are made on two and three-electrode circuits in the oxidation of ethanol in the presence of 2,6-dichlorophenol electron transport mediator. For CFMs 1 and 2 the electron transport by the oxidation of the substrate is not registered, while for CFM 3 the current generation occurs. The resistance of CFM 3 bioelectrode is below the resistance of CFMs 1 and 2 both before (39.6 k Omega/cm(2) for CFM 3, 630 Omega/cm(2) for CFM 2, and 1329 Omega/cm(2) for CFM 1) and after the addition of the substrate (2.9 k Omega/cm(2) for CFM 3, 45 k Omega/cm(2) for CFM 2, and 58 k Omega/cm(2) for CFM 1). The bioelectrode made of CFM 3 has a capacitance of 196 mu F/cm(2)-greater than two orders of magnitude of the bioelectrode capacity of CFMs 1 and 2 (0.51 and 0.58 mu F/cm(2), respectively). It is important to further study the properties of the CFM class of materials, which are promising as the basis of mechanically flexible electrodes with controlled parameters.

Four types of carbon fiber materials (CFMs) obtained by electrospinning polyacrylonitrile solutions are considered. The CFMs intertwine with cells of Gluconobacter oxydans or with their membrane fractions (MFs). Bioelectrochemical characteristics of the electrodes (chrono- and voltamperometric, as well as impedance spectra) are studied. Electrodes are considered a model of the anode of the microbial biofuel cell (MFC). Ethyl alcohol is the oxidized substrate. MALDI-TOF MS demonstrates that MFs retain the protein structure of whole cells and therefore can be used as analogues of whole cells. It is shown that the MFC based on carbon fiber material obtained after 30-min treatment at 1000°C has the highest power and stability. When MFs are used as a biocatalyst, nonmediated charge transfer is observed for all studied CFMs. These results can be successfully used for the design of biosensors and MFCs.

Рассмотрены четыре типа углеродных волокнистых материалов (УВМ), полученных методом электроформования из растворов полиакрилонитрила. УВМ сопрягали с микробными клетками Gluconobacter oxydans или с их мембранными фракциями (МФ). Исследовали биоэлектрохимические характеристики электродов (хронои вольтамперометрические, импедансные спектры). Электроды рассматривали как модель анода микробного биотопливного элемента (мБТЭ); окисляемым субстратом являлся этиловый спирт. Спектры MALDI-TOF MS показали, что МФ сохраняют белковую структуру целых клеток и поэтому могут использоваться как аналоги целых клеток. Показано, что наибольшей мощностью и стабильностью обладал мБТЭ на основе углеродного волокнистого материала, полученного карбонизацией при температуре 1000 °С в течение 30 мин. В случае использования МФ в качестве биокатализатора для всех исследованных УВМ наблюдали безмедиаторный перенос заряда. Полученные результаты могут быть успешно использованы при конструировании биосенсоров и мБТЭ.

We have studied the properties of a bioelectrode formed by the immobilization of Gluconobacter oxydans bacterial cells on carbon superfine materials (CSMs). We use three types of CSMs (as adopted by the working classification CSM 1–3) with different carbonization rates. The bioelectrode is formed by covering the surface of the CSM suspension of bacteria in a chitosan gel. The properties of samples are evaluated by measuring the physiological state of the bacteria immobilized: (a) recording the intensity of cellular respiration, (b) for measuring the charge transport characteristics of electrode (bioelectrocatalysis), and (c) by measuring the electrode impedance. Measurements (b) and (c) are made on two and three-electrode circuits in the oxidation of ethanol in the presence of 2,6-dichlorophenol bacteria electron transport mediator. For CSMs 1 and 2 the electron transport by the oxidation of the substrate is not registered, while for CSM 3 the current generation occurs. The resistance of CSM 3 bioelectrode is below the resistance of CSMs 1 and 2 both before (39.6 kΩ/cm 2 for CSM 3, 630 Ω/cm 2 for CSM 2, and 1329 Ω/cm 2 for CSM 1) and after the addition of the substrate (2.9 kΩ/cm 2 for CSM 3, 45 kΩ/cm 2 for CSM 2, and 58 kΩ/cm 2 for CSM 1). The bioelectrode made of CSM 3 has a capacitance of 196 μF/cm 2 —greater than two orders of magnitude of the bioelectrode capacity of CSMs 1 and 2 (0.51 and 0.58 μF/cm 2 , respectively). It is important to further study the properties of the CSM class of materials, which are promising as the basis of mechanically flexible electrodes with controlled parameters.

Model experiments were carried out to study the microbiological corrosion of concrete by thionic bacteria Acidithiobacillus albertensis DSM 14366T. Concrete samples were exposed in a liquid medium at initial pH 4.0 for 1 month. The corrosion of concrete was assessed by zinc leaching in the medium and sample weight change. The microbiological corrosion caused by the bacteria A. albertensis was shown to decrease if concrete contained 0.10 % nickel sulfide.

The present paper concerns the activity of the microbic biofuel element which oxidizes ethanol. The intact bacterial cells of Gluconobacter oxydans or their membrane fractions were used as a bioelectrocatalyst. Thermoexpanded graphite (TEG) was used as a material of an electrode. The used strain of bacterial cells, as well as carbon composition types will make a basis of a prototype of a microbic biofuel element at development of the block of transformation and accumulation of electric energy.