Microbial biosensors are bioanalytical devices that can measure the toxicity of pollutants or detect specific substances. This is the greatest advantage of microbial biosensors which use whole cells of microorganisms as powerful tools for measuring integral parameters of environmental pollution. This review explores the core principles of microbial biosensors including biofuel devices, emphasizing their capacity to evaluate biochemical oxygen demand (BOD), toxicity, heavy metals, surfactants, phenols, pesticides, inorganic pollutants, and microbiological contamination. However, practical challenges, such as sensitivity to environmental factors like pH, salinity, and the presence of competing substances, continue to hinder their broader application and long-term stability. The performance of these biosensors is closely tied to both technological advancement and the scientific understanding of biological systems, which influence data interpretation and device optimization. The review further examines cutting-edge developments, including the integration of electroactive biofilms with nanomaterials, molecular biology techniques, and artificial intelligence, all of which significantly enhance biosensor functionality and analytical accuracy. Commercial implementations and improvement strategies are also discussed, providing a comprehensive overview of the state-of-the-art in this field. Overall, this work consolidates recent progress and identifies both the potential and limitations of microbial biosensors, offering valuable insights into their future development for environmental monitoring.

Тhe search for new materials with high conductivity and biocompatibility for use in biosensors is an important task. One promising material is bacterial cellulose (BC) due to its high surface area, high porosity, and biocompatibility. In this study, bacterial cellulose is modified with the PEDOT:PSS conductive gel and carbon nanomaterials to increase conductivity. Thermally expanded graphite/BC/PEDOT:PSS/graphene composition is used to immobilize Gluconobacter oxydans acetic-acid bacteria on the surface of a screen-printed carbon electrode. The effect of individual components of the composite on the catalytic activity of bacteria in the presence of 2,6-dichlorophenolindophenol redox mediator is studied. The addition of BC to the composition provides a higher stability of the electrode: the drop in signal within 35 days is 9%. A microbial biosensor based on TEG/PEDOT:PSS/Graphene/BC/ G. oxydans composite show better sensitivity (36.4 µA mM –1 cm –2 ) and lower detection limit (0.005 mM) as well as the widest linear detection range (0.005–2 mM) compared to the other compositions. Thus, bacterial cellulose modified with conductive additives can be applied as a matrix for the immobilization of bacteria in microbial biosensors and microbial fuel cells.

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.

Infections caused by plant pathogens are one of the main causes of the decline in crop yields around the world, which in turn negatively affect the economic situation in many countries. Thus, the detection of plant pathogens is an extremely important task for modern agriculture. Traditional diagnostic methods are quite labour-intensive and not always cost-effective, so new inexpensive, portable and fast methods of pathogen diagnostics are needed. Small-sized devices, such as biosensors, which can be used directly at the sampling site, look very promising for this task. This chapter discusses the main directions of the development of these devices, bioreceptors used to identify various plant pathogens, as well as types of nanomaterials used to modify the devices. The prospects of using nanobiosensors are considered and possible limitations in the development of these devices are discussed.

The development of alternative energy sources is one of the most important areas of modern science. The processes of energy generation are studied in a membraneless mediatorless microbial fuel cell fueled by the Gluconobacter oxydans microorganism using synthetic wastewater with phototrophic Chlorella vulgaris microalgae in the cathode chamber. The operation of the fuel cell is compared with different catholytes, including microalgae with and without illumination, a nutrient medium for growing microalgae, and a K-phosphate buffer. This microbial fuel cell shows stable operation with a slight decrease in power over 113 days of the experiment. This result is due to the formation of biofilms and is confirmed by scanning-electron-microscopy images. Thus, the studied microbial fuel cell is promising for further study in the field of wastewater treatment.

Conductive polymers and their composites are excellent materials for coupling biological materials and electrodes in bioelectrochemical systems. It is assumed that their relevance and introduction to the field of bioelectrochemical devices will only grow due to their tunable conductivity, easy modification, and biocompatibility. This review analyzes the main trends and trends in the development of the methodology for the application of conductive polymers and their use in biosensors and biofuel elements, as well as describes their future prospects. Approaches to the synthesis of such materials and the peculiarities of obtaining their nanocomposites are presented. Special emphasis is placed on the features of the interfaces of such materials with biological objects.

Electropolymerized neutral red, thionine, and aniline were used as part of hybrid nanocomposite conductive polymers, to create an amperometric reagent-less biosensor for glucose determination. The structure of the obtained polymers was studied using infrared (IR) spectroscopy and scanning electron microscopy. Electrochemical characteristics were studied by cyclic voltammetry and impedance spectroscopy. It was shown that, from the point of view of both the rate of electron transfer to the electrode, and the rate of interaction with the active center of glucose oxidase (GOx), the most promising is a new nanocomposite based on poly(neutral red) (pNR) and thermally expanded graphite (TEG). The sensor based on the created nanocomposite material is characterized by a sensitivity of 1000 ± 200 nA × dm3/mmol; the lower limit of the determined glucose concentrations is 0.006 mmol/L. The glucose biosensor based on this nanocomposite was characterized by a high correlation (R2 = 0.9828) with the results of determining the glucose content in human blood using the standard method. Statistical analysis did not reveal any deviations of the results obtained using this biosensor and the reference method. Therefore, the developed biosensor can be used as an alternative to the standard analysis method and as a prototype for creating sensitive and accurate glucometers, as well as biosensors to assess other metabolites.

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.

This work investigated the use of redox-active polymers based on bovine serum albumin and chitosan, covalently bound to mediators neutral red and ferrocene and containing carbon nanotubes, for immobilization of Paracoccus yeei VKM B-3302 bacteria. The structures of produced polymers were studied by IR spectroscopy and scanning electron microscopy. Cyclic voltammetry and impedance spectroscopy found the electrochemical characteristics of the investigated systems: the heterogeneous electron transfer rate constant, the constant of the rate of interaction with P. yeei bacteria and the impedance. The systems containing carbon nanotubes and ferrocene-based redox-active polymer proved to be the most promising. Biosensors formed using the hybrid polymers had a high sensitivity with the lower boundary of 0.1 mg/dm3 of the detected BOD5 concentrations and a high correlation (R = 0.9916) with the standard BOD assay of surface water samples.

This review deals with the use of the highly conductive polymer PEDOT:PSS in biomedical and bioelectrochemical systems. The examples of toxic effects on living cells, positive effects of PEDOT:PSS on the viability of cells and tissues are given. The properties of the polymer, methods of increasing its electrical conductivity by its modification with various nanoparticles and nanomaterials are discussed. Examples of using PEDOT and its composites in bioelectrochemical devices, such as biosensors and biofuel cells, are considered. Changes in the characteristics of biosensors and biofuel cells under the influence of PEDOT are discussed.

The creation of implantable devices that support the functioning of the body is an important area in the field of medical technology. Many of these devices require a power supply, and it is desirable that such sources work during the entire period of implantation, even in the case of a lifelong implant installation. The published data on energy sources for powering implantable and wearable medical devices is reviewed. A comparative assessment of the characteristics of biofuel cells as the most developed version of an implantable energy source with other renewable sources of electric energy based on thermo-, piezo-, electrostatic (ES), magneto-, and photo-converters is given. Particular attention is paid to the use of implantable devices that can serve as a source of energy for low-power systems: micropumps, pacemakers, neuroimplants, etc.