Selenium Nanocomposites in Natural Matrices as Potato Recovery Agent

Copper-Containing Bionanocomposites Based on Natural Raw Arabinogalactan as Effective Vegetation Stimulators and Agents against Phytopathogens

Novel copper-containing bionanocomposites based on the natural raw arabinogalactan have been obtained as universal effective agents against phytopathogen Clavibacter sepedonicus and development stimulants of agricultural plants. Thus, the use of such nanosystems offers a solution to the tasks set in biotechnology while maintaining high environmental standards using non-toxic, biocompatible, and biodegradable natural biopolymers. The physicochemical characteristics of nanocomposites were determined using a number of analytical methods (elemental analysis, transmission electron microscopy and spectroscopic parameters of electron paramagnetic resonance, UV-visible, etc.). The results of the study under the influence of the nanocomposites on the germination of soybean seeds (Glycine max L.) and the vegetation of potatoes (Solanum tuberosum L.) showed the best results in terms of biometric indicators. It is especially worth noting the pronounced influence of the nanocomposite on the development of the root system, and the increase in the mass of the potato root system reached 19%. It is also worth noting that the nanocomposites showed a stimulating effect on the antioxidant system and did not have a negative effect on the content of pigments in potato tissues. Moreover, the resulting bionanocomposite showed a pronounced antibacterial effect against the phytopathogenic bacterium. During the co-incubation of phytopathogen Clavibacter sepedonicus in the presence of the nanocomposite, the number of cells in the bacterial suspension decreased by up to 40% compared to that in the control, and a 10% decrease in the dehydrogenase activity of cells was also detected.

Antibacterial Activity of Dihydroquercetin Separated from Fructus Polygoni orientalis against Clavibacter michiganensis subsp. sepedonicus via Damaging Cell Membrane

The yield and quality of potato can be severely affected by bacterial ring rot, which is caused by Clavibacter michiganensis subsp. sepedonicus (Cms). Recently, using natural compounds to control bacteria has received more attention. In this study, five antibacterial compounds from ethyl acetate (EtOAc) extract of Fructus Polygoni orientalis (FPO) against Cms were isolated and the most active compound was screened. Five active compounds were identified as 3,3'-di-O-methylellagic acid (1), 3,3'-di-O-methylellagic acid-4-O-β-D-glucopyranoside (2), dihydroquercetin (3), protocatechuic acid (4) and quercetin (5). Compound 3 (dihydroquercetin, DHQ) was confirmed as the most active compound. The diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), protective efficiency and curative efficiency of DHQ were 22.50 mm, 0.313 mg/mL, 84.49% and 79.63%, respectively, which exceeded these of thiophanate-methyl (TM) in antibacterial activity assays; this indicated that DHQ had satisfactory antibacterial activities against Cms in vitro and in vivo. Results of cell membrane damage assessments indicated that DHQ could reduce membrane potential (MP), disrupt the cell membrane integrity, and promote the leakage of nucleic acids and proteins. Overall, these findings suggested that DHQ could serve as a promising lead molecular against Cms, which could provide a basis for its further derivatization.

Preparation, characterization, and antioxidant and antiapoptotic activities of biosynthesized nano‑selenium by yak-derived Bacillus cereus and chitosan-encapsulated chemically synthesized nano‑selenium

Nano‑selenium (SeNPs) is a red elemental selenium with extremely small particles, which can be absorbed by the body and has biological activity. Currently, the most commonly used synthetic methods for SeNPs are biosynthesis and chemical synthesis. In this study, YC-3-SeNPs were biosynthesized by a strain of yak-gut Bacillus cereus YC-3, and meanwhile, CST-SeNPs were chemically synthesized and encapsulated with chitosan. A series of characterizations proved that YC-3-SeNPs and CST-SeNPs are spherical particles with excellent stability, and both have an excellent ability to scavenge free radicals in vitro. The particles of YC-3-SeNPs were encapsulated with polysaccharides, fiber, and protein, and it was less toxic than that of CST-SeNPs. Additionally, YC-3-SeNPs and CST-SeNPs may inhibit H₂O₂-induced oxidative stress in cardiomyocytes by activating the Keap1/Nrf2/HO-1 signaling pathway thereby scavenging ROS. Meanwhile, they may exert anti-apoptotic activity in cardiomyocytes by stabilizing mitochondrial membrane potential (∆Ψm) and balancing Bax/Bcl-2 protein, thereby reducing the protein expression of Cyt-c and Cleaved-caspase 3. Given the above, YC-3-SeNPs and CST-SeNPs with excellent antioxidant and anti-apoptotic activities may have broad application potential in the field of cardiovascular diseases.

Novel Nanobiocomposites Based on Natural Polysaccharides as Universal Trophic Low-Dose Micronutrients

New promising manganese-containing nanobiocomposites (NCs) based on natural polysaccharides, arabinogalactan (AG), arabinogalactan sulfate (AGS), and κ-carrageenan (κ-CG) were studied to develop novel multi-purpose trophic low-dose organomineral fertilizers. The general toxicological effects of manganese (Mn) on the vegetation of potatoes (Solanum tuberosum L.) was evaluated in this study. The essential physicochemical properties of this trace element in plant tissues, such as its elemental analysis and its spectroscopic parameters in electron paramagnetic resonance (EPR), were determined. Potato plants grown in an NC-containing medium demonstrated better biometric parameters than in the control medium, and no Mn accumulated in plant tissues. In addition, the synthesized NCs demonstrated a pronounced antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus (Cms) and were proved to be safe for natural soil microflora.

Effect of Natural Polysaccharide Matrix-Based Selenium Nanocomposites on Phytophthora cactorum and Rhizospheric Microorganisms

We studied the effects of new chemically synthesized selenium (Se) nanocomposites (NCs) based on natural polysaccharide matrices arabinogalactan (AG), starch (ST), and kappa-carrageenan (CAR) on the viability of phytopathogen Phytophthora cactorum, rhizospheric bacteria, and potato productivity in the field experiment. Using transmission electron microscopy (TEM), it was shown that the nanocomposites contained nanoparticles varying from 20 to 180 nm in size depending on the type of NC. All three investigated NCs had a fungicidal effect even at the lowest tested concentrations of 50 µg/mL for Se/AG NC (3 µg/mL Se), 35 µg/mL for Se/ST NC (0.5 µg/mL Se), and 39 µg/mL for Se/CAR NC (1.4 µg/mL Se), including concentration of 0.000625% Se (6.25 µg/mL) in the final suspension, which was used to study Se NC effects on bacterial growth of the three common rhizospheric bacteria Acinetobacter guillouiae, Rhodococcus erythropolis and Pseudomonas oryzihabitans isolated from the rhizosphere of plants growing in the Irkutsk Region, Russia. The AG-based Se NC (Se/AG NC) and CAR-based Se NC (Se/CAR NC) exhibited the greatest inhibition of fungal growth up to 60% (at 300 µg/mL) and 49% (at 234 µg/mL), respectively. The safe use of Se NCs against phytopathogens requires them to be environmentally friendly without negative effects on rhizospheric microorganisms. The same concentration of 0.000625% Se (6.25 µg/mL) in the final suspension of all three Se NCs (which corresponds to 105.57 µg/mL for Se/AG NC, 428.08 µg/mL for Se/ST NC and 170.30 µg/mL for Se/CAR NC) was used to study their effect on bacterial growth (bactericidal, bacteriostatic, and biofilm formation effects) of the three rhizospheric bacteria. Based on our earlier studies this concentration had an antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus that causes diseases of potato ring rot, but did not negatively affect the viability of potato plants at this concentration. In this study, using this concentration no bacteriostatic and bactericidal activity of all three Se NCs were found against Rhodococcus erythropolis based on the optical density of a bacterial suspension, agar diffusion, and intensity of biofilm formation, but Se/CAR and Se/AG NCs inhibited the growth of Pseudomonas oryzihabitans. The cell growth was decrease by 15–30% during the entire observation period, but the stimulation of biofilm formation by this bacterium was observed for Se/CAR NC. Se/AG NC also had bacteriostatic and antibiofilm effects on the rhizospheric bacterium Acinetobacter guillouiae. There was a 2.5-fold decrease in bacterial growth and a 30% decrease in biofilm formation, but Se/CAR NC stimulated the growth of A. guillouiae. According to the results of the preliminary field test, an increase in potato productivity by an average of 30% was revealed after the pre-planting treatment of tubers by spraying them with Se/AG and Se/CAR NCs with the same concentration of Se of 0.000625% (6.25 µg/mL) in a final suspension. The obtained and previously published results on the positive effect of natural matrix-based Se NCs on plants open up prospects for further investigation of their effects on rhizosphere bacteria and resistance of cultivated plants to stress factors.