In recent decades, the attention of scientists has been drawn towards nanoparticles (NPs) of metals and metalloids. Traditional methods for the manufacturing of NPs are now being extensively studied. However, disadvantages such as the use of toxic agents and high energy consumption associated with chemical and physical processes impede their continued use in various fields. In this article, we analyse the relevance of the use of living systems and their components for the development of "green" synthesis of nano-objects with exceptional properties and a wide range of applications. The use of nano-biotechnological methods for the synthesis of nanoparticles has the potential of large-scale application and high commercial potential. Bacteria are an extremely convenient target for green nanoparticle synthesis due to their variety and ability to adapt to different environmental conditions. Synthesis of nanoparticles by microorganisms can occur both intracellularly and extracellularly. It is known that individual bacteria are able to bind and concentrate dissolved metal ions and metalloids, thereby detoxifying their environment. There are various bacteria cellular components such as enzymes, proteins, peptides, pigments, which are involved in the formation of nanoparticles. Bio-intensive manufacturing of NPs is environmentally friendly and inexpensive and requires low energy consumption. Some biosynthetic NPs are used as heterogeneous catalysts for environmental restoration, exhibiting higher catalytic efficiency due to their stability and increased biocompatibility. Bacteria used as nanofactories can provide a new approach to the removal of metal or metalloid ions and the production of materials with unique properties. Although a wide range of NPs have been biosynthetic and their synthetic mechanisms have been proposed, some of these mechanisms are not known in detail. This review focuses on the synthesis and catalytic applications of NPs obtained using bacteria. Known mechanisms of bioreduction and prospects for the development of NPs for catalytic applications are discussed.

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In modern conditions, nanomaterials, especially nanoparticles of metals and nonmetals, are increasingly used in various industries. Due to their unique properties, in particular, the ability of nanoparticles to exhibit an enzyme-like effect they are widely used in biology, medicine, biotechnology, the food industry and agriculture. Important advantages of nanoparticles are their size, which enables specific properties to be present: their large surface area, the ability to transfer molecules and the ability to protect them from degradation and release over a long time, the location of action and the specificity of interaction with biological structures. Nanoparticles play a special role in the processes of neutralizing the active forms of oxygen. It has been established that a number of nanoparticles, in particular, Fe, Mn, Zn, Ce, Si and Se oxides, have an enzyme-like activity mimicking that of some enzymes. By changing the degree of oxidation, these particles can regenerate and continuously catalyze the reaction of neutralizing superoxide anion radicals, thus fulfilling the function of SOD and being the first link in protecting tissues and cells from oxidative stress in physiological and pathological conditions. It is proved that nanoparticles Mn3O4, Fe3O4, Co3O4, CeO2, LaCoO3 and other elements can effectively dispose of hydrogen peroxide and other peroxides, showing catalase-like and peroxidase-like activity. Nanozymes are characterized that exhibit the activity of oxidases, peroxidases and phosphatase. The prospect of using mimetics for complex in vitro analyzes of high-sensitivity biomarker disease detection is shown. The possibility of effective multi-use of nanoparticles as antioxidants is indicated. There are good prospects for further research on properties and the use of polyfunctional particles that are easily synthesized, reliable and inexpensive. More work is needed to determine the interaction of enzymomimetics with biological molecules such as proteins, carbohydrates and lipids, and also to take into account the peculiarities of their metabolism, clearance, degradation, biocompatibility and side effects, since individual nanoparticles have the potential to be deposited in separate organs.

Modern industrial poultry farming occupies a leading position in the production of dietary foods, for which it is appropriate to use biologically active substances and probiotics. The study compared the effectiveness of compound feed with the addition of sodium selenite, bio-nano-selenium and L. plantarum in terms of body weight, weight gain, feed consumption and safety of experimental quail. The quails of the Pharaoh meat breed were kept in the vivarium of Bila Tserkva National Agrarian University and by the method of analogues were divided into 4 groups - control and three experimental ones. The duration of the study was 35 days. The results of the study indicate that the use in the quail’s diet of probiotics (L. plantarum) and selenium preparations (sodium selenite and bio-nano-selenium) leads to a predominance of poultry experimental groups in live weight over control analogs. It was found that the growth of bird’s live weight during the experiment differed depending on the use of the Selenium medication or probiotic, and the most intense effect on live weight of quails was the use of bio-nanоselenium in the diet of poultry (11.8% at the end of the experiment). Changes in absolute and average daily body weight gains of experimental birds have been clarified. The use of sodium selenite in the diet of quail caused a tendency for an increase in gains compared with control analogs at the beginning of the study and a downward trend during the fifth week of the study. It was found that the use of probiotics and bio-nano-selenium caused an increase in quail growth, which was more pronounced and reliable when feeding bio-nano-selenium. The obtained results show that probiotic and selenium preparations reduce feed consumption by 1 kg of weight gain, body weight increase by 3.05–11.8% and by 3.3–6.6% increase the safety of the experimental livestock with the best indicators in the group, receiving bio-nano-selenium.

The article is devoted to the mechanisms of regulation of redox processes in cells, a review of the Keap1 / Nrf2 / ARE redox-sensitive signaling system as a fundamental pathway that plays a key role in maintaining cellular redox homeostasis under stressful, inflammatory, carcinogenic and proapoptotic conditions. The structure of the cysteine-rich repressor protein Keap1, which is responsible for sensory perception of electrophiles and reactive oxygen species, the structure and functions of the transcription factor Nrf2, mechanisms of Nrf2 activation through the Keap1 / Nrf2 / ARE signaling system, which regulates the transcription and expression of cellular cytoprotective and antioxidant proteins, are described. Published data on the specificity of the interaction of the components of this cellular signaling pathway, the mechanisms of Keap1 dependent and independent adaptive response to the action of inductors, the role of biogenic selenium nanoparticles synthesized by green chemistry with the participation of bacteria in these processes are analyzed; features of Nrf2 induction depending on the type of bacteria and the stabilizing shell. It has been shown that biogenic selenium nanoparticles (BNSe), synthesized by different types of bacteria, activate the transcription factor Nrf2 using the Keap1-independent activation pathway through mitogen-protein kinases (MAPK): p38, ERK1 / 2 and AKT-mediated phosphorylation of Nrf2, protect the intestinal epithelial barrier function from the effects of oxidative damage, normalize mitochondrial function. A detailed understanding of thiol-dependent and independent redox signaling mechanisms under physiological and pathological conditions will lead to a deeper understanding of the redox component in human and animal diseases. The use of biogenic nanoselen, synthesized with the participation of various bacterial species, has been demonstrated to activate the Keap1 / Nrf2 / ARE signaling pathway, which may be of practical interest as a therapeutic target for many redox-mediated diseases.