Applied Biochemistry and Microbiology最新文献

This review article includes information on the use of coatings, both from chitosan itself and in combination with other polysaccharides and functional compounds, for postharvest processing, mainly of tomatoes, to extend the shelf life of harvested produce. During harvesting of fruit and vegetables, losses due to fungal infection can be as high as 50%. To prevent yield losses and preserve fruit quality, various methods of postharvest treatment are used. Currently, the most effective means used to control postharvest diseases are synthetic fungicides, but their uncontrolled use negatively affects human health and the environment. Recently, there has been a continuing trend to increase the use of natural antimicrobial agents. Such natural compounds can be chitin and chitosan, as they are renewable, biodegradable, have low toxicity, and are safe for consumers and the environment. The film-forming ability of chitosan and its antimicrobial and antioxidant properties are important for obtaining functional coatings for postharvest processing of fruit.

An assessment of the antifungal and immunomodulatory activity of dispersions of chitosan nanoparticles obtained by fractional precipitation at pH 5.0 and pH 7.5 using chitosan of different molecular weights was made. The dispersion of nanoparticles obtained at pH 5 has increased fungistatic activity against C. sativus and A. solani, due to the higher availability of amino groups in looser nanoparticles. This dispersion showed immunostimulating activity, increasing the resistance of wheat to dark brown spot. It was also established that the elicitor activity of dispersions of chitosan nanoparticles is significantly higher than the activity of solutions of the original polymer.

Complexes of lipopolysaccharide (LPS) from the bacterium Escherichia coli and chitosan (CN) with a molecular weight of 5 kDa were obtained and their supramolecular organization was studied. Using atomic force microscopy, it was shown that during the formation of complexes there is a transition from the micellar structure of the original LPS to linear network structures uniformly distributed over the surface of mica. The stability of LPS-CN complexes of various stoichiometries in biological media in the presence of serum proteins was investigated. It was shown that complexes with an LPS–CN ratio of 1 : 1 in the presence of serum proteins lost their surface charge and tended to aggregate while complexes with the maximum saturation of CN (1 : 5) did not aggregate under these conditions and maintained their surface charge. The effect of CNs of different molecular weights on the ability of LPS to interact with neutrophils of human whole blood was studied. It was observed that LPS-CN complexes were capable of binding to neutrophils and internalazing the cell, and this ability was enhanced in the presence of serum proteins. Chitosan exhibited the ability to suppress the synthesis of the proinflammatory cytokine TNF-α induced by LPS, not only as part of the complex but also when cells were pretreated with a polycation.

The influence of multifunctional complexes capable of causing a growth-stimulating effect on plants and inhibiting the development of a wide range of diseases on the Leningradka 6 spring soft wheat cultivar (k-64900) was investigated. In the research, it was found that the application of multifunctional complexes based on the Bacillus subtilis bacterial strains and 0.1% chitosan salicylate in wheat cultivation led to a significant decrease in the incidence of plant diseases: yellow and brown rust, powdery mildew, and root rot and caused an increase in morphometric productivity indicators. This tendency was associated with a significant influence of multifunctional complexes on the increase in the number of primary and nodal roots, the length of nodal roots, productive bushiness, the number of spikelets per spike, and the grains weight per spike. However, the effectiveness of protective and stimulating wheat treatments depended on the complex of natural and climatic factors of wheat vegetation seasons.

The aim of this work was to study the effect of Bacillus subtilis strains VKM B-2604D and VKM B-2605D, which form the basis of the Vitaplan biological product, and their combinations with chitosan salicylate on antioxidant defense enzymes in the process of formation of resistance of wheat plants to infection with the dark brown blotch pathogen Bipolaris sorokiniana. In wheat plants treated with B. subtilis strains and their combinations with chitosan salicylate, upon subsequent infection, catalase and peroxidase are activated, which regulate the intensity of oxidative stress induced by the introduction of the pathogen. Taking the data we obtained into account, it can be assumed that the increase in plant resistance to the pathogen is realized through the control of the activity of antioxidant enzymes (in particular, catalase and peroxidase), which maintain the concentration of H₂O₂ at the level necessary for the neutralization of the phytopathogen in tissues, including the direct destruction of the invading pathogen and/or activation of crosslinking and lignification of the cell wall. These processes strengthen the cell wall and help contain the spread of the pathogen in the plant. At the same time, protective reactions are also switched on, leading to the development of induced resistance in wheat plants to dark brown spotting, which manifests itself in a decrease in the development of the disease by 25–45% relative to the infected control in the treated plants. The results indicate that the combination of active strains of microorganisms-antagonists of plant pathogens and chitosan salicylate is promising for increasing the biological efficiency and expanding the spectrum of action of the developed biological products.