Prikladnaâ biohimiâ i mikrobiologiâ

Aerogel composites were synthesized on the basis of the sodium alginate-chitosan interpolymer complex with the inclusion of calcium carbonate microparticles and supercritical drying. It is shown that the textural characteristics of materials do not depend on the morphology of calcium carbonate particles: the specific surface area of aerogels is almost the same for all materials and amounts to 380–400 m²/g. The developed porous structure of composites along with the polyelectrolyte nature determines their high water absorption — up to 110 g/g. To impart antimicrobial properties, the materials were impregnated with atranorin isolated from the lichen Hypogymnia physodes, which has a pronounced inhibitory effect on the bacterium Proteus mirabilis, which is the main causative agent of wound infections. The minimum suppressive concentration of atranorine is 1 mg/ml. The release of the main amount of atranorine aerosol material included in the matrix occurs within 4 hours and amounts to 50%.

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 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 in human whole blood was studied. It was observed that LPS-CN complexes were capable of binding to neutrophils and entering 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.

An assessment was made 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. 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.

The aim of the 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 into account the data obtained by us, 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, 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 obtained 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 prescription forms of biological products.