Vol 59, No 5 (2023)

The review examines the properties of endophytic bacteria of the genus Bacillus as objects of biocontrol, prospects to expand the spectrum of their protective action based on complexes with chitosan derivatives. The mechanisms of direct and indirect effects of bacteria on the protective potential of plants are described, the role of the pro-/antioxidant system in the formation of systemic protective reactions is analyzed. The immunostimulating properties of chitosan derivatives and its modifications with organic molecules and metal nanoparticles are analyzed. The prospects of using Bacillus spp. bacterial complexes with nano- and submicron particles of chitosan derivatives to expand the spectrum of protective action of new biofungicides and immunostimulants based on them are shown.

Native HydSL hydrogenase of Thiocapsa bogorovii and its modification with truncated C-terminus of HydS (delta54HydS) were shown to be similar in specific activity, thermostability and temperature dependence of activity. It supports the suggestion that C-terminus of HydS does not participate in stabilization of the enzyme structure. Ag⁺ ions irreversibly inactivated both hydrogenases but delta54HydS was more sensitive to this inhibitor. In the presence of Ag⁺ the absorption peak at 410 nm was bleached indicating the destruction of FeS clusters. Protein globule was also destructed by Ag⁺. Prolonged incubation of hydrogenase with Ag⁺ ions led to disappearance of CO and CN peaks in IR spectra indicating NiFe center impairment. Data suggest that the first target of Ag⁺ ions is distal FeS cluster, and C-terminus of HydS interacts with Ag⁺ decreasing local ion concentration near the distal FeS cluster.

Based on the yeast Kluyveromyces lactis, a strain-producer of recombinant alpaca prochymosin (Vicugna pacos) was developed. A comparative analysis of the biochemical properties of recombinant alpaca chymosin obtained in the expression systems of K. lactis and Escherichia coli was carried out. It was found that the recombinant alpaca chymosin synthesized in K. lactis exceeds the analog obtained in E. coli by 12.9 times in the number of enzyme turnovers, and by 2.9 times in catalytic efficiency. Compared to chymosin expressed in E. coli, the enzyme obtained in a eukaryotic producer has a thermal stability threshold increased by 5°C. Replacing a prokaryotic producer with a eukaryotic one enhances the negative sensitivity of the milk-clotting activity of recombinant alpaca chymosin to an increase in substrate pH in the range of 6.1–6.9, which is accompanied by an increase in the duration of coagulation by 8–35%. With an increase in the concentration of CaCl2 in the substrate, the coagulation activity of the target enzyme synthesized in E. coli was 12–14% higher than that of its analogue obtained in K. lactis.

In this work, a comparative analysis of the profile of fatty acids (FA) and volatile organic compounds (VOCs) for skimmed cow’s milk fermented by four different probiotic strains of Lacticasibacillus paracasei (ABK, KF1, MA2 and MA3) was carried out. Analysis of FA and VOC profiles was performed using gas chromatography with mass spectrometric detection (GC-MS). For additional visualization of odor changes and its intensity in the fermented milk samples, the E-nose “electronic nose” odor analyzer was used. In total, presence of 42 different FA was detected in all samples, of which 17 were saturated, 8 monounsaturated, and 5 polyunsaturated. The strain-specific differences between the studied samples were of a complex nature and could not be explained only by the variation in the contribution of several individual FAs. The FA-nutritional indices, characterizing the nutritional and biological value of the samples, were different for milk fermented by different strains. Analysis of VOCs showed that the main odor-forming compounds in the studied samples were FAs and their reaction products, 2-heptanone, 2-nonanone, and 2-nonanol, formed as a result of the following chain of transformations: β-oxidation → decarboxylation → reduction. The aroma of L. paracasei fermentation products, predicted on the basis of the odors of individual VOCs, generally coincided with their organoleptic assessment – a flavor typical of fermented milk (yogurt, curdled milk) with floral and fruity notes.

The article discusses the influence of caffeic acid (CA), its mix with chitosan (CHT + CA) and chitosan-based conjugate (CHT-CA) on growth and proline content of microclone potato plants (Solanum tuberosum L.) in in vitro culture under optimal conditions and under prolonged osmotic stress caused by polyethylene glycol. Under optimal conditions CHT-CA and CA, acting as moderate strength stressors, accelerate the growth and development of potato microclones and increase the proline accumulation in the stems. Under osmotic stress CA and CHT-CA promote the resistance of potato microclones and maintain their active growth. And such effect persists during the reparation period. The mechanical mix CHT + CA causes inhibition of microclonal plants’ growth and development accompanied by a significant accumulation of proline which is aggravated under stress.