Natural Humic Substances Research Articles

The Influence of Silver-Containing Bionanomaterials Based on Humic Ligands on Biofilm Formation in Opportunistic Pathogens.

The uncontrolled use of antibiotics has led to a global problem of antimicrobial resistance. One of the main mechanisms of bacterial resistance is the formation of biofilms. In order to prevent the growth of antimicrobial resistance, it is crucial to develop new antibacterial agents that are capable of inhibiting the formation of biofilms. This makes this area of research highly relevant today. Promising candidates for these antibacterial agents are new bionanomaterials made from natural humic substances and silver nanoparticles. These substances have the potential to not only directly kill microorganisms but also penetrate biofilms and inhibit their formation. The goal of this study is to synthesize active pharmaceutical substances in the form of bionanomaterials, using ultradispersed silver nanoparticles in a matrix of coal humic substances, perform their characterization (NMR spectroscopy, TEM, and ICP-AES methods), and research their influence on biofilm formation in the most dangerous opportunistic pathogens (E. coli, Methicillin-resistant St. Aureus, K. pneumoniae, P. aeruginosa, St. aureus, A. baumannii, and K. Pneumonia). The results showed that all of the studied bionanomaterials had antibacterial activity against all of the opportunistic pathogens. Furthermore, they were found to have a suppressive effect on both pre-existing biofilms of these bacteria and their formation.

Unraveling the structural intricacy of synthetic humic substance via, UV-vis, FTIR, 13C NMR and non-targeted silylation-GC-Orbitrap MS

Phenolic precursors combined with Maillard precursors can be converted into humic-acid like polycondensate during oxidation either via catalysis or non-catalysis processes. Current work was conducted on structural elucidation of synthetic humic substances (SHS) by avoiding alkaline extraction, using silylation coupled with high resolution mass spectrometery, while utilizing the mass spectral data of trimethylsilyl (TMS) derivatives. SHS mimicking natural humic substances was prepared by a bottom-up approach via polycondensation of catechol and Maillard precursors (glucose/glycine) at mild temperature (50 °C) and alkaline pH conditions. Reaction was monitored via UV–vis spectroscopy during the time period of 25 days by measuring the UV–vis curves. FTIR and 13C NMR curves were compared with IHSS Leonardite HA, gallic acid-protocatechuic acid-humic acid-like polycondensate (GA-PA-HALP), catechol: vanillic acid oligomer via oxidative coupling (CAVA) and corn straw HA via hydrothermal synthesis. SHS was subjected to silylation (BSTFA+1 %TMCS) in two solvents (pyridine or ethyl acetate) and then characterized via non-targeted analysis of GCOrbitrap MS. Mass spectrometery (MS) data showed that TMS fragments included more acidic and glucose oxidation moieties along with presence of Maillard reaction moieties. While remaining TMS fragments consisted of amines, aldehydes, ketones, amides, phenols etc. as well as conjugated moieties, adducts, quinones and oxidation/reduction moieties of catechol. Current method suggests that the combination of silylation with high-resolution gas chromatography-mass spectrometery (GCOrbitrap MS) offers an alternative approach for characterizing substances formed in biotic or abiotic reactions, as well as in water-extracted dissolved organic matter samples.

Lime-assisted hydrothermal humification and carbonization of sugar beet pulp: Unveiling the yield, quality, and phytotoxicity of products

Hydrothermal carbonization (HTC) solid and liquid products may inhibit seed germination, necessitating post-treatment. The hydrothermal humification (HTH) method addresses this drawback by transforming inhibitory compounds, such as aromatics, into artificial humic acids (AHAs) and artificial fulvic acids (AFAs). This study introduces a novel approach by investigating the substitution of the commonly used alkaline agent in HTH, KOH, with hydrated lime to develop cost-effective hydrothermal fertilizers from sugar beet pulp, enriching them with AHAs. It assesses the effects of lime on AHA production and soluble organic compounds compared to KOH. The results indicate that lime significantly reduces furans (from 560 to 3.15 mg/kg DM in solid and from 344 to 3.86 mg/L in process liquid) and boosts sugars and organic acids, especially lactic acid (from 4.70 to 65.82 g/kg DM in solid and from 4.05 to 22.89 mg/L in process liquid), increasing hydrochar yield (68.8% with lime vs. 27.4% with KOH). Despite the lower AHA production with lime compared to KOH (3.47% vs. 15.50%), lime-treated hydrothermal products are abundant in calcium and magnesium, boasting a pH of 7. This property presents a safer and more efficient alternative to hydrothermal fertilizers. The characterization of AHAs aligns with standard and natural humic substances, while lime-assisted HTH products, applied at a level of 0.01% w/w, could significantly enhance wheat growth and nutrient uptake compared to the control group. Importantly, these products show no toxicity on Daphnia magna, underscoring their potential for sustainable agriculture.

Solid-Phase Extraction at High pH as a Promising Tool for Targeted Isolation of Biologically Active Fractions of Humic Acids.

A search for novel sources of biologically active compounds is at the top of the agenda for biomedical technologies. Natural humic substances (HSs) contain a large variety of different chemotypes, such as condensed tannins, hydrolyzable tannins, terpenoids, lignins, etc. The goal of this work was to develop an efficient separation technique based on solid-phase extraction (SPE) for the isolation of narrow fractions of HS with higher biological activity compared to the initial material. We used lignite humic acid as the parent humic material, which showed moderate inhibition activity toward beta-lactamase TEM 1 and antioxidant activity. We applied two different SPE techniques: the first one was based on a gradient elution with water/methanol mixtures of the humic material sorbed at pH 2, and the second one implied separation by a difference in the pKa value by the use of sequential sorption of HS at pH from 8 to 3. SPE cartridges Bond Elute PPL (Agilent) were used in the fractionation experiments. The first and second techniques yielded 9 and 7 fractions, respectively. All fractions were characterized using high-resolution mass spectrometry and biological assays, including the determination of beta-lactamase (TEM 1) inhibition activity and antioxidant activity. The acidity-based separation technique demonstrated substantial advantages: it enabled the isolation of components, outcompeting the initial material at the first step of separation (sorption at pH 8). It showed moderate orthogonality in separation with regard to the polarity-based technique. Good perspectives are shown for developing a 2D separation scheme using a combination of polarity and acidity-based approaches to reduce structural heterogeneity of the narrow fractions of HS.

Complex Restoration of Oil-Contaminated Soils with New Organomineral Reagents

Among pollutants, petroleum hydrocarbons are recognized as the priority pollutants of the environment. Petroleum hydrocarbons can cause changes in the physical and chemical properties of soils, leading to a decrease in the functional activity of the microbiota of soil biocenoses. The aim of the study was to develop ways and methods of oil-contaminated soil remediation with the new generation sorbents based on organomineral biofertilizer “Kazuglegumus” and aluminum alloys activated by indium, gallium, and tin. The structure and composition of the organomineral reagents, as well as soils with different degrees of contamination were proved by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, and thermogravimetry. As a working hypothesis, it was accepted that the aluminum alloy activated by gallium, indium, and tin forms complex compounds with humic or fulvic acids, which are low-toxic or non-toxic for plants. The efficiency of cleaning oil-contaminated soils with organomineral sorbents was evaluated. The reduction of oil concentration in soil samples by 12–22% depending on the concentration of reagents and oil content in soil was revealed. The character of oil pollution impact on plants of legume families alfalfa, melilot, and sainfoin, which are characterized by the ability to accumulate and then give nitrogen to the soil, was studied. The phytotoxicity of uncontaminated and non-oil-contaminated soils was studied in laboratory and field conditions. Significantly accelerated plant growth was observed in samples of oil-contaminated soil after treatment with sorbent based on activated aluminum alloy Rau-85 and fertilizer “Kazuglegumus”. The plants had stronger root systems. These experiments are explained by the effect of Rau-85 alloys in favor of reducing the oil concentration to the normalized limits, as well as the transformation of natural humic substances and additionally applied fertilizer “Kazuglegumus” (potassium humates), which increased their biological activity.

Exolaccase Propels Humification to Decontaminate Bisphenol A and Create Humic-like Biostimulants.

Exolaccase-propelled humification (E-PH) helps eliminate phenolic pollutants and produce macromolecular precipitates. Herein, we investigated the influencing mechanism of 12 humic precursors (HPs) on exolaccase-enabled bisphenol A (BPA) decontamination and humification. Catechol, vanillic acid, caffeic acid, and gentian acid not only expedited BPA removal but also created large amounts of copolymeric precipitates. These precipitates had rich functional groups similar to natural humic substances, which presented great aromatic and acidic characteristics. The releasing amounts of BPA monomer from four precipitates were 0.08-12.87% at pH 2.0-11.0, suggesting that BPA-HP copolymers had pH stability. More excitingly, certain copolymeric precipitates could stimulate the growth and development of radish seedlings. The radish growth-promotion mechanisms of copolymers were involved in two aspects: (1) Copolymers interacted with root exudates to accelerate nutrient uptake; (2) Copolymers released auxins to provoke radish growth. These results may provide an innovative strategy for decontaminating phenolic pollutants and yielding humic-like biostimulants in E-PH.

The Effect of Dietary Humic Substances on Cellular Immunity and Blood Characteristics in Piglets

This study’s objective was to determine the impact of dietary humic substances on immune response and blood profiles in piglets. A total of 24 crossbred piglets (Slovakian White × Landrace; 35 days old; average body weight of 11.67 kg) were allotted to two dietary groups with (experimental; 5 g·kg−1) or without (control; 0 g·kg−1) natural humic substances supplementation. In this study, we observed a significant increase of the proportion of CD4+CD8- lymphocytes (p < 0.001) in the experimental group. The results also showed a tendency for an increase of the phagocytic activity and the engulfing capacity of phagocytes and the numbers of the other monitored lymphocyte subpopulations (CD3+, CD21+, CD4-D8+, CD4+CD8+, CD4+CD25+) in piglets in the experimental group compared to the control group. Supplementation of humic substances increased serum alkaline phosphatase compared to the control group (p < 0.05). Other monitored blood parameters were not significantly affected by dietary treatment. It concluded that inclusion of humic substances in the diet of piglets could have a stimulating effect on cellular immunity, without a negative effect on haematological and biochemical parameters.

Response of common bean to plant growth promoting rhizobacteria under different levels of phosphorus

The usage of biofertilizer as alternative or support to mineral fertilizer encourage continuously due to fertilizer cost and environmental pollution. The effect of three phosphorus doses (0, 30, and 60 kg ha-1 P2O5) with a control and different commercial biofertilizers, Bontera (Bacillus amyloliquefociens, Bacillus pumilus, Bacillus subtilis, Bacillus licheniformis, Bacillus megaterium, Trichoderma harzianum, Trichoderma kanigi), Bactoboost (Bacillus subtilis, Bacillus magaterium, Loctococcus spp.), Koklendirici (Bacillus subtilis, Bacillus magaterium, Loctococcus spp.), Lifebac NP (Bacillus subtilis, Bacillus magaterium), natural organic matter and humic substances (NSAH) (15% organic matter, 6% organic carbon, 13% humic + fulvic acid), and Rhizobia (Rhizobium leguminosorum)) were investigated. Increasing phosphorus doses positively affected all the investigated characters. Koklendirici biofertilizer positively affected the important yield components, but highest grain yield was determined in the NSAH plots. Increasing phosphorus (P) doses did not affect nitrogen (N), potassium (K), magnesium (Mg), and copper (Cu) contents of the grain while phosphorus, calcium (Ca), iron (Fe), manganese (Mn), and zinc (Zn) contents showed an increase. Difference in climate might have influenced these results. These results indicated that understanding of bio and mineral fertilizer would enable us to use biofertilizer as an alternative to mineral fertilizer to common bean production.

The effect of coal-derived humic substances and their silver-containing bionanocomposites on arginine balance in peritoneal macrophages of intact mice

Background. Antigen-presenting cells (APCs), especially macrophages, play an important role in the body defense against various pathogens. Their dysfunction and polarization are associated with most inflammatory and autoimmune diseases. The inflammatory process is regulated by activation and / or inhibition of genes differentially expressed by macrophages. Successful correction of inflammation leads firstly to elimination of inflammatory stimuli and then to remodeling and restoration of tissues and organs. It was experimentally confirmed that silvercontaining bionanocomposites based on natural humic substances (HS) obtained from coal of different origin, as well as initial matrices of these HS, are capable of activating pro- and anti-inflammatory properties of macrophages.Aim. To study cytotoxic, pyrogenic, and immunomodulatory properties (arginine balance) of initial HS samples and samples of silver nanoparticles ultradispersed in these HS matrices (HS-AgNPs) in the cell culture of peritoneal macrophages, as well as their effect on pro- and anti-inflammatory properties of APCs.Materials and methods. Cultural and biochemical methods were used in the study.Results. The study showed that the samples CHE-K, CHE-AgNPs, CHS-K, and CHP-K increased M1 macrophage polarization due to stimulation of the NO-synthase activity and inhibition of arginase. The samples CHI-K, CHIAgNPs, CHP-AgNPs, and CHS-AgNPs modulated an alternative M2 or M2-like state of macrophage activation. At the same time, HS are not cytotoxic at effective concentrations, and three out of four studied samples did not contain pyrogenic impurities.Conclusion. The use of HS and their silver-containing bionanocomposites, which have the ability to greatly affect the polarization of antigen-presenting cells, is a promising research area in correction of the inflammatory response for solving an important social and medical problem of treating chronic wounds.

НАНОКОМПОЗИТИ СРІБЛА НА ОСНОВІ СИНТЕТИЧНИХ ГУМІНОВИХ РЕЧОВИН ЯК ВИСОКОЕФЕКТИВНІ СТИМУЛЯТОРИ РОСТУ РОСЛИ

Introduction. Nanotechnology have positive impact in improving many sectors of economy including agriculture. Silver nanoparticles (AgNPs) have been implicated nowadays to enhance seed germination, plant growth, improvement of photosynthetic quantum efficiency and as antimicrobial agents to manage plant diseases.Despite the known growth-stimulating activity of preparations of humic substances and silver nanoparticles, there is currently no information on the effect on growth processes of composites containing silver nanoparticles encapsulated in macromolecules from synthetic humic substances. It is expected that such combined nanopreparations have enhanced and complementary properties of a metal core and a shell of humic synthetic substances.Purpose. The aim of this study was to investigate the growth-stimulating activity of silver nanocomposites based on synthetic humic substances derived from quercetin, and to determine the range of active concentrations in the process of germination of wheat seeds.Methods. The received silver nanoparticles are characterized by UV–visible spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy and transmission electron microscopy (TEM). To study the growth-stimulating activity of synthetic humic substances and silver nanocomposites, a series of solutions was prepared on their basis by dilution with a logarithmic decrease in concentration from 1·10–1 to 4·10-16%.Result. Nanobiocomposites containing silver nanoparticles and synthetic humic substances were synthesized in the reaction of reduction of silver ions with synthetic humic substances obtained in laboratory conditions from quercetin.Preference of synthetic humic substances over natural humic substances is determined by a standardization problem resolution due to the strict control of conditions of the HS formation that expands the areas of application of the silver nanoparticles made on their basis. The high crystallinity of nanobiocomposites with fcc phase is evident from XRD patterns. The TEM results show that the silver nanoparticles are spherical in shape with average size about 9.6 nm. The FTIR spectroscopic study confirmed that the synthetic humic substances have ability to perform dual functions of reduction and stabilization of silver nanoparticles.The growth-promoting activity of synthetic humic substances and silver nanocomposites based on them was studied on the example of germination of wheat seeds of the variety "Zolotokosa" according to standard procedures. It is established that aqueous solutions of synthetic humic substances and silver 54 Серія «Біологічні науки», 202 2nanocomposites based on them in a wide range of concentrations have a complex effect on the growth and development of wheat seeds. It is shown that seed germination increases (by 2–40%) and the length of the main root (by 9–100%) of wheat germ increases. It should be noted that synthetic humic substances and silver nanocomposites based on them to a greater extent stimulate root growth, which is important for agriculture in arid areas. The ranges of effective concentrations of solutions of the studied drugs show the maximum total stimulating activity (by the number of germinated seeds and the length of the main root compared to the control) during germination of wheat seeds for synthetic humic substances and for silver nanocomposite - 10-10-10-4%. Stimulation of root growth by silver nanocomposites based on synthetic humic substances in most concentrations exceeds the effect of the original humic substances.Originality. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Conclusion. It has been established that silver nanocomposites based on synthetic humic substances exhibit highly effective growth-stimulating activity. The ranges of active concentrations of the studied preparations demonstrate the optimal stimulating activity for synthetic humic substances and silver nanocomposite based on them by the number of germinated seeds 1·10–10–1·10–4 %, by the length of the main roots compared to the control - 1· 10-12-1· 10-4%. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Key words: synthetic humic substances; silver nanocomposites; growth-promoting activity; wheat

Reduction of structural Fe(III) in nontronite by humic substances in the absence and presence of Shewanella putrefaciens and accompanying secondary mineralization

Abstract Studies have shown the electron shuttling role of humic substances (HS) in enhancing microbial reduction of solid-phase Fe(III), but it is unknown if native HS can reduce structural Fe(III) in clays and how their chemical properties affect this process and secondary mineralization. The objective of this study was to evaluate the role of natural HS, Leonardite humic acid (LHA), and Pahokee Peat humic acid (PPHA) in reducing structural Fe(III) in nontronite with or without Shewanella putrefaciens. The extent of Fe(III) reduction was determined with a wet chemical method. Electrochemical methods, spectroscopy, and mass spectrometry were used to determine the changes of HS electrochemical and molecular composition after bioreduction. X-ray diffraction and electron microscopy were used to observe mineralogical transformations. The results showed that natural HS not only served as an electron donor to abiotically reduce Fe(III) in nontronite but also served as an electron shuttle to enhance Fe(III) bioreduction by S. putrefaciens. In the presence of CN32 cells, both the rate and extent of Fe(III) reduction significantly increased. Between the two HS, PPHA was more effective. The final bioreduction extents were 12.2 and 17.8% with LHA and PPHA, respectively, in bicarbonate buffer. Interestingly, when CN32 cells were present, LHA and PPHA donated more electrons to NAu-2, suggesting that CN32 cells were able to make additional electrons of LHA and PPHA available to reduce structural Fe(III). Although LHA reduced less Fe(III), it induced more extensive mineral transformation. In contrast, PPHA reduced more Fe(III) but did not induce any mineralogical change. These contrasting behaviors between the two humic acids are ascribed to their differences in electron-donating capacity, reactive functional group distribution, and metal complexation capacity. A unique set of secondary minerals, including talc, illite, silica, albite, ilmenite, and ferrihydrite formed as a result of reduction. The results highlight the importance of coupled C and Fe biogeochemical transformations and have implications for nutrient cycling and contaminant migration in the environment.

Directed Synthesis of Humic and Fulvic Derivatives with Enhanced Antioxidant Properties

Redox moieties, which are present in the molecular backbone of humic substances (HS), govern their antioxidant properties. We hypothesized that a directed modification of the humic backbone via incorporation of redox moieties with known redox properties might provide an efficient tool for tuning up antioxidant properties of HS. In this work, hydroquinonoid and hydronaphthoquinonoid centres were used, which possess very different redox characteristics. They were incorporated into the structure of coal (leonardite) humic acids CHA) and peat fulvic acids (PFA). For this goal, an oxidative copolymerization of phenols was used. The latter was induced via oxidation of hydroquinones and hydroxynapjtaquinones with a use of Fenton’s reagent. The structure of the obtained products was characterized using NMR and FTIR spectroscopy. H/D labelling coupled to FT ICR mass spectrometry analysis was applied for identification of the reaction products as a tool for surmising on reaction mechanism. It was shown that covalent -C-C- bond were formed between the incorporated redox centers and aromatic core of HS. The parent humic acids and their naphthoquinonoid derivatives have demonstrated high accepting capacity. At the same time, fulvic acids and their hydroquinonoid derivatives have possessed both high donor and high antioxidant capacities. The kinetic studies have demonstrated that both humic acids and their derivatives showed much slower kinetics of antioxidant reactions as compared to fulvic acids. The obtained results show, firstly, substantial difference in redox and antioxidant properties of the humic and fulvic acids, and, secondly, they can serve as an experimental evidence that directed chemical modification of humic substances can be used to tune and control antioxidant properties of natural HS.

Inhibition of Class A β-Lactamase (TEM-1) by Narrow Fractions of Humic Substances.

Antimicrobial resistance is a global threat. The use of biologically active natural products alone or in combination with the clinically proven antimicrobial agents might be a useful strategy to fight the resistance. The scientific hypotheses of this study were twofold: (1) the natural humic substances rich in dicarboxyl, phenolic, heteroaryl, and other fragments might possess inhibitory activity against β-lactamases, and (2) this inhibitory activity might be linked to the molecular composition of the humic ensemble. To test these hypotheses, we used humic substances (HS) from different sources (coal, peat, and soil) and of different fractional compositions (humic acids, hymatomelanic acids, and narrow fractions from solid-phase extraction) for inhibiting serine β-lactamase TEM-1. Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) was used to characterize the molecular composition of all humic materials used in this study. The kinetic assay with chromogenic substrate CENTA was used for assessment of inhibitory activity. The inhibition data have shown that among all humic materials tested, a distinct activity was observed within apolar fractions of hymatomelanic acid isolated from lignite. The decrease in the hydrolysis rate in the presence of most active fractions was 42% (with sulbactam—87%). Of particular importance is that these very fractions caused a synergistic effect (2-fold) for the combinations with sulbactam. Linking the observed inhibition effects to molecular composition revealed the preferential contribution of low-oxidized aromatic and acyclic components such as flavonoid-, lignin, and terpenoid-like molecules. The binding of single low-molecular-weight components to the cryptic allosteric site along with supramolecular interactions of humic aggregates with the protein surface could be considered as a major contributor to the observed inhibition. We believe that fine fractionation of hydrophobic humic materials along with molecular modeling studies on the interaction between humic molecules and β-lactamases might contribute to the development of novel β-lactamase inhibitors of humic nature.

Comparative assessment of the use of humic substances derived from brown coals for technogenic landscapes reclamation

The objective of the study. To identify the prospects for the use of humic preparations for the restoration of disturbed coal-mining areas, by assessing the relationship between their biological activity and the structural-group composition. Location and time of the study. The study was carried out in the Novokuznetsk district of the Kemerovo region (N 54.14o N and E 87.10o E) in 2020. Methodology. The study of the structure-group composition of humic preparations was carried out by the 13C NMR spectroscopy. Evaluation of the effect of humic preparations was performed in a series of plot experiments setup in the reclaimed and non-reclaimed areas of the coal mining spoils. The properties of the soils substrates of the technogenic landscapes were determined by traditional soil methods. The effect of the preparations was assessed by the dry phytomass production and pod yields of Vícia villósa vetch, as well as the phytomass production of the Avéna satíva + Vícia villósa mixture. Statistical analysis of the data was carried out by the principal components analysis. Main results: Comparison of humic preparations obtained from brown coals of the Tisulsky (Kansk-Achinsky basin) and Tyulgansky (South Ural basin) deposits showed that, in general, all preparations positively affected phytomass production and pod yeild. However, in different conditions of technogenic landscapes and in relation to different plant species, the effect could manifest itself in different directions. A stable positive effect from pre-sowing seed treatment was achieved only with substrates depleted in natural humic substances (humus and peat), and with optimal moisture. Under such conditions, the greatest influence was exerted by preparations obtained from brown coals of the Tisulsky deposit of the Kansk-Achinsky basin, and their naturally oxidized form, which are characterized by a high proportion of oxygen-containing aliphatic (CO-Alk-O), as well as aromatic (СAr) groups. At the same time, under moisture deficit, the indicated chemical properties negatively affected the yield. In stony areas of technogenic landscapes, a positive effect was manifested only by preparations with a maximum proportion of aromatic hydroxide-containing groups (СAr-ОН). Enrichment of humic preparations with microelements (Zn and Cu) did not result in either positive or negative consequences. Conclusion. The use of humic preparations obtained from brown coals for restoring technogenic landscapes is justified only in areas composed of loamy rocks with a low content of humic substances of humus and peat. The noted multidirectional action of humates, which manifests itself depending on their structural and group composition, properties of substrates and plant species used at the biological stage of reclamation, indicates that using the same standardized preparations for the reclamation of various technogenic objects may not be reasonable.

Calcium Phosphate Particles Coated with Humic Substances: A Potential Plant Biostimulant from Circular Economy.

Nowadays, the use of biostimulants to reduce agrochemical input is a major trend in agriculture. In this work, we report on calcium phosphate particles (CaP) recovered from the circular economy, combined with natural humic substances (HSs), to produce a plant biostimulant. CaPs were obtained by the thermal treatment of Salmo salar bones and were subsequently functionalized with HSs by soaking in a HS water solution. The obtained materials were characterized, showing that the functionalization with HS did not sort any effect on the bulk physicochemical properties of CaP, with the exception of the surface charge that was found to get more negative. Finally, the effect of the materials on nutrient uptake and translocation in the early stages of development (up to 20 days) of two model species of interest for horticulture, Valerianella locusta and Diplotaxis tenuifolia, was assessed. Both species exhibited a similar tendency to accumulate Ca and P in hypogeal tissues, but showed different reactions to the treatments in terms of translocation to the leaves. CaP and CaP–HS treatments lead to an increase of P accumulation in the leaves of D. tenuifolia, while the treatment with HS was found to increase only the concentration of Ca in V. locusta leaves. A low biostimulating effect on both plants’ growth was observed, and was mainly scribed to the low concentration of HS in the tested materials. In the end, the obtained material showed promising results in virtue of its potential to elicit phosphorous uptake and foliar translocation by plants.

Advantages and limits to copper phytoextraction in vineyards.

Copper (Cu) contamination of soils may alter the functioning and sustainability of vineyard ecosystems. Cultivating Cu-extracting plants in vineyard inter-rows, or phytoextraction, is one possible way currently under consideration in agroecology to reduce Cu contamination of vineyard topsoils. This option is rarely used, mainly because Cu phytoextraction yields are too low to significantly reduce contamination due to the relatively "low" phytoavailability of Cu in the soil (compared to other trace metals) and its preferential accumulation in the roots of most extracting plants. This article describes the main practices and associated constraints that could theoretically be used to maximize Cu phytoextraction at field scale, including the use of Cu-accumulating plants grown (i) with acidifying plants (e.g., leguminous plants), and/or (ii) in the presence of acidifying fertilizers (ammonium, elemental sulfur), or (iii) with soluble "biochelators" added to the soil such as natural humic substances or metabolites produced by rhizospheric bacteria such as siderophores, in the inter-rows. This discussion article also provides an overview of the possible ways to exploit Cu-enriched biomass, notably through ecocatalysis or biofortification of animal feed.

Quercetin as a precursor in the synthesis of analogues of fulvic acids and their antibacterial properties

A simple, fast and effective method for producing synthetic substances with properties similar to natural humic substances has been proposed. The synthesis method is based on the oxidation of quercetin by molecular oxygen in an alkaline medium, followed by conversion to the acid form by passing through a cation exchange column. Study of elemental and functional compositions, spectral properties (UV/Vis and IR range) and redox characteristics allowed qualifying the resulting product as a synthetic fulvic acid. The enhanced antibacterial properties of the obtained synthetic product were established. The minimum concentration of inhibition of synthetic fulvic acid derived from quercetin is 25 g mL–1, which is in 100 times less than for natural humic substances.

Which Traits of Humic Substances Are Investigated to Improve Their Agronomical Value?

Humic substances (HSs) are chromogenic organic assemblies that are widespread in the environment, including soils, oceans, rivers, and coal-related resources. HSs are known to directly and indirectly stimulate plants based on their versatile organic structures. Their beneficial activities have led to the rapid market growth of agronomical HSs. However, there are still several technical issues and concerns to be addressed to advance sustainable agronomical practices for HSs and allow growers to use HSs reliably. First, it is necessary to elucidate the evident structure (component)–function relationship of HSs. Specifically, the core structural features of HSs corresponding to crop species, treatment method (i.e., soil, foliar, or immersion applications), and soil type-dependent plant stimulatory actions as well as specific plant responses (e.g., root genesis and stress resistance) should be detailed to identify practical crop treatment methodologies. These trials must then be accompanied by means to upgrade crop marketability to help the growers. Second, structural differences of HSs depending on extraction sources should be compared to develop quality control and assurance measures for agronomical uses of HSs. In particular, coal-related HSs obtainable in bulk amounts for large farmland applications should be structurally and functionally distinguishable from other natural HSs. The diversity of organic structures and components in coal-based HSs must thus be examined thoroughly to provide practical information to growers. Overall, there is a consensus amongst researchers that HSs have the potential to enhance soil quality and crop productivity, but appropriate research directions should be explored for growers’ needs and farmland applications.

СИНТЕТИЧНІ ФУЛЬВОКИСЛОТИ З ТАНІНУ

This research introduces a new, simple and effective method of producing synthetic fulvic acids from tannin. The synthesis is based on the reaction of tannin oxidation by pure oxygen in a highly alkaline environment. The conversion of fulvates to the acid was achieved by passing the resulting mixture through a cation-exchange column in the H-form. The resulting dark-brown product solution has a pH = 2. A complex study of the physicochemical and spectroscopic properties of the obtained product using the methods of elemental analysis, ultraviolet-visible, infra red and electron paramagnetic resonance spectroscopy, scanning electron microscopy, X-ray diffraction showed the similarity of the obtained product to natural fulvic acids. Synthetic fulvic acids are advantageous over natural humic substances due to their reproducible properties as a result of their strict synthesis conditions. This significantly expands the scope of their application, in particular in medicine, where one of the prerequisites is the standardization of properties.

How the Supramolecular Nature of Lignohumate Affects Its Diffusion in Agarose Hydrogel.

Lignohumate, as an industrially produced analog of natural humic substances, is studied from the point of view of its diffusion properties. This work focuses on its permeation ability, important in agricultural and horticultural applications, connected with its penetration into plant organs as leaves and roots. The hydrogel based on agarose was used as a model material for the diffusion of lignohumate. Two types of experiments were realized: the diffusion of lignohumate in the hydrogel diffusion couple and the diffusion of lignohumate from its solution into hydrogel. The diffusion coefficient of lignohumate in the hydrogel was determined and used for the modelling of the time development of concentration profiles. It was found that the model agrees with experimental data for short times but an accumulation of lignohumate in front of the interface between donor and acceptor hydrogels was observed after several days. The particle size distribution of lignohumate and changes in the E4/E6 ratio used as an indicator of molecular weight of humic substances were determined. The results showed that the supramolecular structure of lignohumate can react sensitively to actual changes in its environs and thus affect their mobility and permeability into different materials. A filtration effect at the interface can be observed as an accompanying phenomenon of the re-arrangement in the lignohumate secondary structure.