pH Changes Research Articles

Specialized contact sites regulate the fusion of chlamydial inclusion membranes

The intracellular bacterial pathogen Chlamydia trachomatis replicates within a membrane-bound compartment called the inclusion. Upon infection with several chlamydiae, each bacterium creates its own inclusion, resulting in multiple inclusions within each host cell. Ultimately, these inclusions fuse together in a process that requires the chlamydial protein IncA. Here, we show that inclusions form unique contact sites (inclusion contact sites, ICSs) prior to fusion, that serve as fusogenic platforms in which specific lipids and chlamydial proteins concentrate. Fusion depends on IncA clustering within ICSs and is regulated by PI(3,4)P2 and sphingolipids. As IncA concentrates within ICSs, its C-terminus likely interacts in trans with IncA on the apposing membrane, securing a high concentration of IncA at fusion sites. This regulatory mechanism contrasts with eukaryotic or viral fusion systems that are either composed of multiple proteins or use a change in pH to initiate membrane fusion. Thus, our study demonstrates that Chlamydia-mediated membrane fusion is primarily regulated by specific structural domains in IncA and its local organization on the inclusion membrane, which is affected by the host cell lipid composition.

Exploring the Presence of Cannabinoids in Hemp-Infused Fermented Milk Drinks: An Analysis of Pre- and Post-Fermentation Levels.

Yoghurts are the most popular fermented dairy products. Consumer attention is directed towards products containing inputs that enrich the product with bioactive substances. The growing interest in the Cannabis sativa L. plant has resulted in the development of a market for hemp products. The main aim of this research work was to determine the effect of the lactic fermentation process on the stability of cannabinoids in fermented milk beverages containing hemp inputs (hemp oil, dried hemp, ethanolic hemp extract) at 0.5, 1 and 2% (w/v). The effect of the type of hemp input on the technological process (i.e., pH value, viability of LAB during 28 days of storage) was also checked and the sensory quality of the prepared samples was evaluated. It was shown that the choice of type/form and amount of hemp addition influenced the final cannabinoid content of the product after fermentation and post-fermentation, but no effect on the survival of yoghurt bacteria or pH changes during storage was confirmed. Fermented milk drinks containing hemp oil had the highest cannabinoid content. The QDA results of the sensory evaluation of the yoghurts show that the most acceptable product in terms of overall quality is the yoghurt containing 0.5% hemp extract and 2% hemp oil.

Enhancing Antioxidant Activity from Aquatic Plant Cymodocea nodosa for Cosmetic Formulation Through Optimized Ultrasound-Assisted Extraction Using Response Surface Methodology

This study aimed to enhance antioxidant extraction from the aquatic plant Cymodocea nodosa for cosmetic formulation through optimized ultrasound-assisted extraction using response surface methodology. The optimized conditions—30 min of extraction time, 30% ultrasonic power, and 25% hydro-ethanolic solvent—resulted in a high total phenolic content of 113.07 mg EAG/g DM and antioxidant activity of 67.02%. Chromatographic analysis revealed a rich profile of phenolic compounds, including sinapic acid (0.741 mg/g), myricetin (0.62 mg/g), and quercetin-3-O-rutinoside (0.3 mg/g), demonstrating the extract’s potent therapeutic properties. While the extract exhibited limited anti-inflammatory activity, it showed no cytotoxic effects on RAW 267.4 cells, ensuring its safety for cosmetic applications. The formulated cream maintained stable pH (6.58 to 6.6), consistent viscosity (5966.38 to 5980.6 cp), and minimal color changes over a 30-day period, indicating robust stability across various temperatures (4 °C, 25 °C, and 40 °C). These results confirm the potential of C. nodosa extracts to develop effective, stable, and eco-friendly cosmetic products, offering substantial benefits for skin health and emphasizing the importance of sustainable extraction processes in the cosmetics industry.

Effects of pH on Enzyme Activity in Pakistan

Purpose: The aim of the study was to assess the effects of pH on enzyme activity in Pakistan. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study indicated that effects of pH on enzyme activity are significant because enzymes are highly sensitive to the pH levels in their environment. Each enzyme has an optimal pH at which it functions most efficiently. Deviations from this optimal pH can lead to a decrease in enzyme activity. At extreme pH levels, enzymes may become denatured, altering their structure and impairing their ability to bind to substrates. This is because changes in pH can affect the ionic bonds and hydrogen bonds within the enzyme, altering its active site. As a result, enzyme activity typically increases as the pH approaches the optimal level, and decreases when the pH moves away from this point. Therefore, maintaining proper pH levels is crucial for the effective functioning of enzymes in biological systems. Implications to Theory, Practice and Policy: Lock and key model, induced fit theory and chemical equilibrium theory may be used to anchor future studies on the effects of pH on enzyme activity in Pakistan. In practical applications, industries utilizing enzymes should prioritize the implementation of rigorous pH monitoring and control systems to maintain optimal conditions for enzymatic activity. From a policy perspective, it is crucial for policymakers to establish clear guidelines governing the use of enzymes in industrial applications, with a particular emphasis on the importance of pH control in achieving optimal performance.

A Review of Advanced Hydrogel Applications for Tissue Engineering and Drug Delivery Systems as Biomaterials

Hydrogels are known for their high water retention capacity and biocompatibility and have become essential materials in tissue engineering and drug delivery systems. This review explores recent advancements in hydrogel technology, focusing on innovative types such as self-healing, tough, smart, and hybrid hydrogels, each engineered to overcome the limitations of conventional hydrogels. Self-healing hydrogels can autonomously repair structural damage, making them well-suited for applications in dynamic biomedical environments. Tough hydrogels are designed with enhanced mechanical properties, enabling their use in load-bearing applications such as cartilage regeneration. Smart hydrogels respond to external stimuli, including changes in pH, temperature, and electromagnetic fields, making them ideal for controlled drug release tailored to specific medical needs. Hybrid hydrogels, made from both natural and synthetic polymers, combine bioactivity and mechanical resilience, which is particularly valuable in engineering complex tissues. Despite these innovations, challenges such as optimizing biocompatibility, adjusting degradation rates, and scaling up production remain. This review provides an in-depth analysis of these emerging hydrogel technologies, highlighting their transformative potential in both tissue engineering and drug delivery while outlining future directions for their development in biomedical applications.

Switchable pH-Responsive Morphologies of Coassembled Nucleobase Copolymers.

This work presents supramolecular coassembled nucleobase copolymers with transitional morphologies upon pH changes (from 7.4 to 10). Uracil- and adenine-containing copolymers were prepared by RAFT, which allowed us to finely tailor the polymerization degree and the composition. The coassembled formulations prepared in an aqueous buffer at two distinct pH (7.4 and 10) formed spherical morphologies at physiological pH. The increase of the pH induced the apparition of various large, irreversible anisotropic supramolecular architectures. Isothermal titration calorimetry revealed that the coassembly at pH 7.4 was mainly guided by H-bonds between complementary nucleobases, while the experiments conducted at pH 10 showed that the assemblies were mainly driven by hydrophobic interactions. These results highlight that the nature of supramolecular interactions (H-bonds or hydrophobic interactions) has a great influence on the morphology of nucleobase-containing coassemblies when changing the pH. These findings may provide further perspectives in the field of advanced nanomaterials.

Hydrological cycle amplification imposes spatial patterns on the climate change response of ocean pH and carbonate chemistry

Abstract. ​​​​​​​Ocean CO2 uptake and acidification in response to human activities are driven primarily by the rise in atmospheric CO2 but are also modulated by climate change. Existing work suggests that this “climate effect” influences the uptake and storage of anthropogenic carbon and acidification via the global increase in ocean temperature, although some regional responses have been attributed to changes in circulation or biological activity. Here, we investigate spatial patterns in the climate effect on surface ocean acidification (and the closely related carbonate chemistry) in an Earth system model under a rapid CO2-increase scenario and identify a different driving process. We show that the amplification of the hydrological cycle, a robustly simulated feature of climate change, is largely responsible for the spatial patterns in this climate effect at the sea surface. This “hydrological effect” can be understood as a subset of the total climate effect, which includes warming, hydrological cycle amplification, circulation, and biological changes. We demonstrate that it acts through two primary mechanisms: (i) directly diluting or concentrating dissolved ions by adding or removing freshwater and (ii) altering the sea surface temperature, which influences the solubility of dissolved inorganic carbon (DIC) and acidity of seawater. The hydrological effect opposes acidification in salinifying regions, most notably the subtropical Atlantic, and enhances acidification in freshening regions such as the western Pacific. Its single strongest effect is to dilute the negative ions that buffer the dissolution of CO2, quantified as alkalinity. The local changes in alkalinity, DIC, and pH linked to the pattern of hydrological cycle amplification are as strong as the (largely uniform) changes due to warming, explaining the weak increase in pH and DIC seen in the climate effect in the subtropical Atlantic Ocean.

Tapping below the lateral line does not reduce maple sap yield or quality

Modern maple sugaring operations use vacuum tubing systems to enhance sap flow and maximize yield. The positioning of tapholes is a crucial aspect influencing tree health and sap yields, but is limited by dropline length. Inverting droplines to expand the tappable zone and reduce the risk of over-tapping has raised concerns about vacuum efficiency and microbial contamination.We examined over 2200 trees on multiple high-vacuum 5/16″ tubing systems at two sites over three seasons, tapping at various heights above and below the lateral line. Our analysis showed no significant decrease in sap yield or sugar concentration when tapping below the lateral line. Taps at extreme heights above the lateral line produced slightly more sap (estimated at 0.6 l of sap per tap for a good production season) and marginally sweeter sap (0.06 °Brix). However, differences in vacuum management had a more significant impact on yield. Additionally, there was no evidence of increased microbial activity or changes in sap pH due to relative tapping height.These findings demonstrate that tapping below the lateral line effectively doubles the tappable zone without significantly affecting sap yield or quality, promoting sustainable maple sugaring practices by ensuring long-term productivity without compromising sap yields or quality.

Dual-Responsive PIL Films with Gold Nanoparticles: Tailoring Electrical Responses to pH and Thermal Stimuli.

In recent years, stimuli-responsive poly(ionic liquids) (PILs) have attracted great attention. The stimuli-dependent properties, particularly the electrical properties, of multiresponsive PILs incorporating functionalized nanoparticles, however, have been less investigated. In this work, we present the synthesis, characterization, and application of PIL films incorporating pH- and thermoresponsive hybrid materials composed of gold nanoparticles functionalized with poly(2-(dimethylamino)ethyl methacrylate) (Au@PDMAEMA). The Au@PDMAEMA nanoparticles exhibit distinct responsiveness to changes in environmental pH and temperature, thereby altering the electrical properties of the PIL films blended with responsive gold nanoparticles (PIL w/Au). This research not only fills a gap in the study of electrical properties of multiresponsive nanoparticle-incorporated PILs but also extends the potential applications of PILs in various fields, including smart sensors and electronic devices.

Vine Tea Extract Enhanced the Fermentation of Skimmed Milk by Lacticaseibacillus casei

ABSTRACTVine tea extract (VTE), from the traditional Chinese herbal tea, was added to reconstituted skimmed milk; the mixture was fermented with Lacticaseibacillus casei, and fermentation characteristics, flavonoid content, antioxidant capacity (AOC), and viability of L. casei were measured. 2 mg/mL VTE promoted L. casei growth and 8 mg/mL VTE inhibited growth, an effect consistent with observed pH changes. Total flavonoid content and AOC increased with increasing VTE dosage. Dihydromyricetin was partially metabolized during fermentation and accounted for most of the antioxidant function of VTE. 2 mg/mL VTE was optimal for maintenance of probiotic culture and pH stability during cold storage and improved AOC during product shelf life. VTE has the potential to increase the health benefits of probiotic dairy products, and the resulting mixture may be suitable to use as a daily milk‐based health drink.

Cryopreservation, cryoprotectants, and potential risk of epigenetic alteration.

The cryopreservation of gametes and embryos has increased notably over the past 20years and is now an essential part of assisted reproductive technologies (ARTs). However, because the cryopreservationprocess is un-physiological for human cells, gametes, and embryos, cryobiologists have suggested diverse methods to successfully cryopreserve human gametes and embryos in order to maintain their viability and assure successful pregnancy. During the first period of early development, major waves of epigenetic reprogramming-crucial for the fate of the embryo-occur. Recently, concerns relating to the increased incidence of epigenetic anomalies and genomic-imprinting disorders have been reported after ARTs and cryopreservation. Epigenetic reprogramming is particularly susceptible to environmental and un-physiological conditions such as ovarian stimulation, embryo culture, and cryopreservation that might collectively affect epigenetics dysregulation. Additionally, recent literature suggests that epigenetic and transcriptomic profiles are sensitive to the stress induced by vitrification, osmotic shock, oxidative stress, rapid temperature and pH changes, and cryoprotectants; it is therefore critical to have a more comprehensive understanding of the potential induced perturbations of epigenetic modifications that may be associated with vitrification. The aim of this paper is to present a critical evaluation of the association of gamete and embryo cryopreservation, use of cryoprotectants, and epigenetic dysregulations with potential long-term consequences for offspring health.

Elevated endoplasmic reticulum pH is associated with high growth and bisAb aggregation in CHO cells.

Chinese hamster ovary (CHO) bioprocesses, the dominant platform for therapeutic protein production, are increasingly used to produce complex multispecific proteins. Product quantity and quality are affected by intracellular conditions, but these are challenging to measure and often overlooked during process optimization studies. pH is known to impact quality attributes like protein aggregation across upstream and downstream processes, yet the effects of intracellular pH on cell culture performance are largely unknown. Recently, advances in protein biosensors have enabled investigations of intracellular environments with high spatiotemporal resolution. In this study, we integrated a fluorescent pH-sensitive biosensor into a bispecifc (bisAb)-producing cell line to investigate changes in endoplasmic reticulum pH (pHER). We then investigated how changes in lactate metabolism impacted pHER, cellular redox, and product quality in fed-batch and perfusion bioreactors. Our data show pHER rapidly increased during exponential growth to a maximum of pH 7.7, followed by a sharp drop in the stationary phase in all perfusion and fed-batch conditions. pHER decline in the stationary phase was driven by an apparent loss of cellular pH regulation that occurred despite differences in redox profiles. Finally, we found protein aggregate levels correlated most closely with pHER which provides new insights into product aggregate formation in CHO processes. An improved understanding of the intracellular changes impacting bioprocesses can ultimately help guide media optimizations, improve bioprocess control strategies, or provide new targets for cell engineering.

Synthesis and self-assembly of perylene-cored poly(amidoamine) dendrimers with poly[2-(dimethylamino)ethyl methacrylate]-modified arms as fluorescent bio-imaging probes and doxorubicin carriers

A poly(amidoamine) (PAMAM) dendrimer is prepared using a divergent method, with perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) as luminescent core. The peripheral amines are modified using α-bromoisobutyryl bromide, allowing the dendrimers to act as macroinitiators for the synthesis of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) through atom transfer radical polymerization (ATRP) with three different degrees of polymerization. The successful synthesis is verified by conducting a range of analyses, including Fourier-transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and X-ray diffraction (XRD). Additionally, the impact of changes in solution pH on the self-assembly of dendrimers is explored. Field emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) showed unique morphologies, including spherical micelles and cubic-hexagonal structures, at varying pH levels. The self-assembled dendrimers are utilized to load doxorubicin (DOX) and the drug release kinetics are studied under various conditions. The biocompatibility of the dendrimers is assessed using the MTT assay against SH-SY5Y cells. Additionally, higher dendrimer generations improved the solubility, compatibility, and fluorescent properties of the core. The dendrimers' capacity for cellular uptake and fluorescence imaging is also evaluated using SH-SY5Y cells, demonstrating their effectiveness in live-cell fluorescence imaging.

The impact of reservoirs on the soils of adjacent areas: overview of global and local aspects

AbstractThis study aims to analyze the impact of reservoirs on the soils of surrounding areas to elucidate potential ecological consequences. To achieve this goal, a territorial analysis of the soil surrounding such reservoirs as the Kyiv, Kaniv, Kremenchuk, and Kakhovka, which constitute the Dnieper Cascade of Reservoirs, was conducted. The study found that the average soil pH changes in reservoirs range from 6.0 to 7.5, while nitrogen and phosphorus content in the soil varies from 0.2% to 1.5% and from 0.1% to 0.5%, respectively. Average changes in the content of humic substances and fulvic acids in the reservoirs range from 1.0 to 3.5 and from 0.2 to 1.5 mg/L, respectively. Furthermore, it was found that the creation of large reservoirs on the Dnieper River is accompanied by significant consequences for shoreline soils. The geomorphological study of the reservoirs within the Dnieper Cascade revealed their diversity in terms of shoreline types. Some have more erodible shores, indicating vulnerability to erosion, as observed in the Kakhovka Reservoir, while others have more neutral shores less susceptible to erosion, such as the Kremenchuk Reservoir. The distribution of humic substances in the reservoirs of the Dnieper Cascade is determined by the hydrological structure and water inflows, with the highest concentrations in the upper regions. Decreased flow velocity in the lower part of the cascade leads to the deposition of humic substances in bottom sediments. The threat to ecological systems is exacerbated by incidents such as the catastrophe at the Kakhovka Hydroelectric Power Station in 2023, which triggered a serious ecological crisis with a wide range of consequences. Consequently, the application of a comprehensive approach to water resource management and environmental protection becomes crucial. This entails meticulous planning of construction, implementation of ecological technologies, and engaging the public in the water resource management process.

Antioxidant potential of olive leaf (<i>Olea europaea</i> L.) sustainable extracts evaluated <i>in vitro</i> and minced beef meat

In this work, by using water steam only, two antioxidant extracts were obtained from olive leaves (Olea europaea L.), a by-product of olive oil chain. Olive leaf extracts (OLEs) were tested as such (water extract: WE) and partially purified with ethyl acetate (ethyl acetate [EA] extract). Total phenols were 7.4 mg/mL and 3.8 mg/mL in WE and EA final solutions, respectively, evidencing a different composition by high-performance liquid chromatography analysis. Both extracts were evaluated in vitro in comparison to pure hydroxytyrosol (Hy). A 2,2-diphenyl-1-picrylhydrazyl (DPPH) EC50 of 57.6, 76.5, and 39.7 µg/mL and a ferric reducing antioxidant power EC50 of 84.8, 69.9, 41.2 µg/mL were determined for WE, EA, and Hy solution, respectively. The Rancimat induction time determined at 120°C in a lard sample with 200-ppm total phenol equivalent addition of WE, EA, and Hy was 8.92 h, 12.74 h, and 7.27 h, respectively (vs. 2.24 h for lard only). Extracts were added at the same dose (200 ppm) to minced beef patties that were put in closed containers under controlled air headspace composition (NA, natural air; HOA, modified air with 80% O2; and 20% N2) and stored at 4°C up to 10 days. Extracts showed significant effectiveness in contrasting decrease of O2 level in containers as well as pH and color changes of patties. A significant increase (expressed as mg of malondialdehyde MDA/kg; thiobarbituric acid-reactive substance (TBARS) assay was conducted in control samples at an interval of 0–10 days (from 0.52 to 0.78 mg of MDA/kg in NA samples; and from 0.55 to 1.31 mg of MDA/kg in HOA samples), while minimal changes were observed in treated samples. These findings suggest a potential use of OLEs for maintaining quality and oxidative stability of beef patties during storage.

Donor–π bridge-acceptor dyes featuring dual chromophoric groups for enhanced sensitivity in wearable sweat sensor

The pH value of human sweat serves as a crucial biomarker for disease diagnosis, rendering wearable sweat sensors an innovative tool for monitoring human health. However, the commercialization of these devices is seriously impeded by their low sensitivity, poor wearing comfort, and limited reusability. In this work, a reactive dye capable of color change under pH change has been synthesized. Due to the unique molecular structure, the dye molecule exhibits remarkable color change recognition and high sensitivity. To fabricate a wearable pH sensor, screen printing technology was employed for depositing the color-changing dye onto cotton fabric. The resulting sensor demonstrated excellent performance attributes including high color sensitivity, robust cyclic stability in response to pH changes, and exceptional resistance against washing, friction, and sunlight-induced fading. Therefore, this study presents a highly promising approach for achieving real-time monitoring of human sweat pH levels.

Unveiling the heterojunction of Fe3O4@MXene nanocatalyst for ultrafast degradation of antibiotics via non-radical pathway

The transfer of advanced oxidation processes (AOPs) to real-world applications faces several technology challenges involving oxidation performance, catalyst cost, poor reactive oxygen species (ROS) yield, and long-term stability. This work aims to develop a reactive, efficient, and stable MXene-based nanocatalyst, namely Fe3O4@Ti3C2Tx, for ultrafast removal of the selected sulfonamide antibiotics. As revealed by extensive nanocatalyst characterization, the MXene surface not only anchors Fe/Fe3O4 nanoparticles (NPs) but also prevents NP agglomeration. Notably, the conductive interface between MXene and Fe3O4 promotes the Fe(II)/Fe(III) redox cycle and accelerates peroxymonosulfate (PMS) activation. The Fe3O4@Ti3C2Tx demonstrates excellent catalytic activity by achieving complete sulfamethoxazole (SMX) degradation within 6 min and maintained its catalytic activity after 5 continuous cycles. In the Fe3O4@Ti3C2Tx/PMS system, multiple ROS (e.g., •OH, SO4•-, O2•-) are involved but 1O2 was found to be the primary ROS for SMX degradation. The presence of co-exiting inorganic impurities and pH changes may hinder SMX degradation. Finally, elucidating possible degradation pathways of SMX would greatly aid in treating antibiotic-containing wastewater.

Metal organic frameworks (MOFs)-based fluorescent CA125 analysis: A comparative study of the quenching effects of MIL-101, Cu-MOF, ZIF-8, UiO-66

Metal-organic frameworks (MOFs) are a class of materials with highly ordered pore structures. Due to their unique physical and chemical properties, they show great potential in the field of biosensors. Some MOFs can adsorb fluorescently labeled nucleic acid aptamers through various interaction mechanisms (such as electrostatic interactions, π-π stacking, hydrogen bonding, etc.). These interactions not only ensure the stable binding of the aptamers but also allow for their controlled release under specific conditions (such as changes in pH, temperature, or the presence of specific molecules). This mechanism provides multiple possibilities for the design of biosensors. Herein, we have systematically compared the quenching effects of widely used MOFs that can bind to aptamers, i.e., Fe-MOF (MIL-101), Cu-MOF, Zn-MOF (ZIF-8) and Zr-MOF (UiO-66). The study on the kinetics, quenching efficiency, and influencing factors such as ionic strength pH and temperature is performed. Interestingly, Cu-MOF exhibits superior quenching abilities to the other three materials in both the quenching efficiency and kinetics. Thus, a Cu-MOF based fluorescent sensor is reported to detect the ovarian cancer marker carbohydrate antigen 125 (CA125), which provides convenient detection performance (assay time about 10 min), and a detection range from 0.1 to 400 ng/mL. Moreover, it is designed in a simple mix-and-detect format and can be directly applied to clinical sample detection. This work may offer guidance for the choice of MOFs and elaborate design of biosensors.

Microbial community composition and co-occurrence network analysis of the rhizosphere soil of the main constructive tree species in Helan Mountain of Northwest China

To understand the microbial diversity and community composition within the main constructive tree species, Picea crassifolia, Betula platyphylla, and Pinus tabuliformis, in Helan Mountain and their response to changes in soil physicochemical factors, a high throughput sequencing technology was used to analyze the bacterial and fungal diversity and community structure. RDA (Redundancy Analysis) and Pearson correlation analysis were used to explore the influence of soil physicochemical factors on microbial community construction, and co-occurrence network analysis was conducted on the microbial communities. The results showed that the fungal and bacterial diversity was highest in B. platyphylla, and lowest in P. crassifolia. Additionally, the fungal/bacterial richness was greatest in the rhizosphere soils of P. tabuliformis and B. platyphylla. RDA and Pearson correlation analysis revealed that NN (nitrate nitrogen) and AP (available phosphorus) were the main determining factors of the bacterial community, while NN and SOC (soil water content) were the main determining factors of the fungal community. Pearson correlation analysis between soil physicochemical factors and the alpha diversity of the microbial communities revealed a significant positive correlation between pH and the bacterial and fungal diversity, while SOC, TN (total nitrogen), AP, and AN (available nitrogen) were significantly negatively correlated with the bacterial and fungal diversity. Co-occurrence network analysis revealed that the soil bacterial communities exhibit richer network nodes, edges, greater diversity, and greater network connectivity. Indicating that bacterial communities exhibit more complex and stable interaction patterns in soil. This study reveals the complex interactive relationship between microbial communities and soil physicochemical factors in forest ecosystems. By analyzing the response of rhizosphere microbial communities of major tree species in Helan Mountain to nutrient dynamics and pH changes, we can deepen our understanding of the role of microorganisms in regulating ecosystem functions and provide theoretical basis for soil improvement and ecological restoration strategies.

Release of selected nutrients from polymer-coated fertilisers in the soil environment

The aim of the study was to evaluate the release of NH4-N and PO4-P from polymer-coated fertilisers in the soil environment, and to analyse their impact on pH and conductivity of the soil leachates. In this investigation mineral NPK(S) 6-20-30(7) fertiliser (as a starting material), commercial, controlled-release OsmocoteTM fertiliser (as a reference material) and four polymer-coated fertilisers have been used. Biodegradable polybutylene(succinate-co- dilinoleate), polyethylene(succinate-co-terepftalate) and chitosan have been used as coating materials. The experiments were conducted in the laboratory conditions, in PVC columns filled with air-dry soil. The nutrients release from the investigated materials was explained based on the diffusion mechanism and it was interpreted with the use of the Korsmeyer–Peppas kinetic model. Two mechanisms dominate in the release process of nutrients: the mechanism based on quasi-Fickian diffusion and non-Fickian (anomalous case) mechanism. The largest changes of pH and electrical conductivity (EC) of soil leachates occurred in the initial period of research for all tested fertilisers (pH: 9.5–20.3% – loamy sand (S1) 7.9–20.6% – sandy loam (S2); EC: 438–1667% – S1, 771–1509% – S2). The polymer coating significantly reduces the nutrient release from the fertiliser core. The size of these changes depends on the type and thickness of the polymer layer and the physicochemical properties of the soils.