Search Results (173)

The rapid detection of organophosphorus (OP) compounds is crucial for safeguarding human health and ensuring food safety. This study presents a novel wearable electrochemical biosensor that integrates miniaturized screen-printed electrodes with wearable devices to achieve real-time, on-site OP detection. The biosensor was fabricated by constructing a screen-printed carbon electrode (SPCE) on a thermoplastic polyurethane (TPU) substrate, sequentially modified with graphene (GR), gold nanoparticles (AuNPs), and organophosphorus hydrolase (OPH), and finally encapsulated with Nafion. This SPCE/GR/AuNPs/OPH/Nafion configuration yields a highly flexible and portable device. The detection principle relies on the enzymatic hydrolysis of methyl paraoxon (MPOX) by OPH, generating p-nitrophenol (PNP), which is quantitatively measured via square wave voltammetry (SWV). The sensor exhibits a broad linear detection range (30–400 μM) with a strong linear correlation (R² = 0.995) and a low detection limit (0.321 μM). It demonstrates excellent selectivity against common interfering substances, including urea, sucrose, and various metal ions. Application to real-world samples such as cabbage and tap water yielded high recoveries (107.2% for cabbage and 101.2% for tap water), with relative standard deviations (RSDs) below 8%. Furthermore, the biosensor maintains robust flexibility and mechanical resilience, with less than 5% signal loss after 100 bending cycles, confirming its suitability for wearable applications and reliable operation under mechanical stress. This innovative, flexible electrochemical biosensor provides a powerful and reliable platform for rapid OP detection, particularly in complex testing environments. Full article

Mandarin fish (Siniperca chuatsi) is a carnivorous fish species endemic to China with significant economic value. The Recirculating Aquaculture System (RAS) has exhibited promising application prospects in the culture of this species. However, the role of the succession patterns of microbial community structure in maintaining the ecological function and stability of this system remains poorly understood. Therefore, this study employed 16S rRNA high-throughput sequencing to analyze community characteristics, assembly mechanisms, co-occurrence networks, and potential functions across different functional zones and culture cycles. The results indicated that, temporally, alpha diversity decreased significantly during the T4 stage due to stress from nutrient accumulation and metabolic waste, accompanied by a distinct succession of dominant taxa. As the system entered the T5 stage, self-purification capacity improved, and microbial diversity gradually recovered. Spatially, significant differences in microbial composition were observed across environments, reflecting the strong influence of environmental specificity on community structure. Analysis of assembly mechanisms revealed that stochastic processes played a dominant role in driving the microbial community, particularly during the T3–T4 stages and within the YCS and TSC zones. Conversely, microbial dispersal was limited in the GC and LHC zones due to habitat barriers. Co-occurrence network analysis demonstrated that microbial interactions were predominantly competitive, with the network structure shifting from loose to modular over time. Spatially, differentiation arises due to varying functional requirements. Functional prediction identified chemoheterotrophy as the core metabolic function. Furthermore, the nitrogen transformation pathway shifted from predominantly denitrification to urea hydrolysis and nitrate reduction as the culture period progressed. These findings highlight the risk of nitrite and ammonia nitrogen accumulation in later stages and provide a theoretical basis for the optimization and management of RAS for Mandarin fish. Full article

Soil salinization and heavy metal pollution represent significant global challenges to farmland sustainability and food security. Globally, over 800 million hectares of land are affected by salinity, with approximately 17% of cultivated land exhibiting concentrations of at least one heavy metal exceeding established agricultural safety thresholds. Microbially Induced Calcium Carbonate Precipitation (MICP) is an innovative biogeochemical process that harnesses microbial metabolic activities to facilitate soil mineralization. The core mechanism involves ureolytic microorganisms hydrolyzing urea to produce carbonate ions (CO₃²⁻). These ions subsequently react with environmental calcium ions (Ca²⁺) to form insoluble calcium carbonate (CaCO₃) precipitates. This review synthesizes recent research progress on the application of MICP technology for the remediation of heavy metal pollution. It elucidates the mechanistic pathways by which MICP immobilizes heavy metal ions and critically evaluates its potential application for ameliorating heavy metal contamination specifically within saline–alkaline soils. Key challenges impeding the broader practical deployment of MICP are analyzed, particularly concerning salt-alkali stress tolerance and the management of ammonia emissions during urea hydrolysis. Emerging strategies, such as the synergistic integration of MICP with biochar amendments, offer promising solutions. Biochar can provide a protective microenvironment for microbial consortia and potentially mitigate ammonia volatilization, thereby enhancing the overall efficacy and feasibility of this remediation approach for contaminated saline–alkaline lands. Full article

Rhizosphere nitrogen-fixing bacteria play a critical role in sustainable crop production by enhancing nitrogen availability and improving soil fertility. This study aimed to isolate and characterize native rhizospheric nitrogen-fixing bacteria (NRNFB) associated with baby maize (Zea mays L.) roots and evaluate their nitrogen-fixing potential. Thirty root samples were collected, and ten bacterial isolates (V1–V10) were obtained using selective media. Morphological, biochemical, and physiological analyses identified strain V3 as the most promising candidate, exhibiting strong growth on nitrogen-free Burk medium and high oxidase, catalase, and urea hydrolysis activities. The strain demonstrated broad environmental tolerance, including salinity up to 4% NaCl, temperatures ranging from 15 to 45 °C, and pH values between 5.0 and 8.0. Molecular identification based on 16S rRNA gene sequencing revealed 100% sequence similarity with Peribacillus simplex LT4 (strain LT4). Nitrogenase activity analysis showed a peak during the exponential growth phase, accompanied by increased nitrogen accumulation in the culture medium, confirming active biological nitrogen fixation. These findings highlight the physiological adaptability and functional efficiency of strain LT4, supporting its potential development as a biofertilizer for sustainable maize production systems. Full article

Objectives: While several physiological functions of milt peptides have been discovered, the structural characteristics of Theragra chalcogramma milt peptides (TMP) and their anti-fatigue mechanisms remain unclear. Methods: TMP was obtained by hydrolysis via flavor enzyme and alkaline protease, and its structural characteristics were analyzed. A mice model of exercise-induced fatigue was established. The anti-fatigue effect of TMP was evaluated by determining the main biochemical indices in the serum, liver, and skeletal muscle of mice. Additionally, qPCR analysis was conducted to investigate its regulatory effects on relevant energy metabolism pathways. Results: TMP contained 18.2% branched-chain amino acids, with those with molecular weights below 1000 Da accounting for 91.6%. A total of 154 characteristic peptides, such as VPFPR and LPPGR, were identified from TMP, among which 64% of the peptides contained glutamic acid, arginine, or aspartic acid. Molecular docking of potential bioactive peptides to AMP-activated protein kinase (AMPK) revealed binding energies from −9.1 to −5.5 kcal/mol. The exhaustive swimming test showed that oral administration of TMP prolonged the swimming duration. In the fatigue murine model, TMP reduced blood urea nitrogen and blood lactic acid levels while enhancing the content of muscle glycogen. Meanwhile, TMP significantly increased the activity of glutathione peroxidase and superoxide dismutase and reduced the accumulation of malondialdehyde, demonstrating antioxidant properties. Additionally, TMP significantly decreased creatine kinase and lactate dehydrogenase extravasation, thereby protecting muscle tissue, as corroborated by immunohistochemical analyses. Mechanistically, TMP upregulated AMPK and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) expression, promoting mitochondrial biogenesis via the AMPK/PGC-1α pathway. Conclusions: These findings suggest TMP has potential as a dietary supplement for alleviating physical fatigue. Full article

The reliable quantification of urea in agricultural systems requires methods that combine metrological rigor with low environmental impact. This work develops and validates a micro-Raman method (λ = 532 nm) for the direct determination of urea in aqueous solutions and soils. The method is formally compared with the reference procedure ISO 19746:2017 (HPLC). Calibration, based on the 1000–1200 and 1460–1670 cm⁻¹ windows, showed near-ideal linearity in the 0.25–25% w/w range (r² = 0.9999). LOD and LOQ values were 0.178 and 0.735% w/w, respectively. Intra- and inter-day accuracy proved adequate for routine use (RSD ≤ 5%). A one-way ANOVA (p = 0.983) confirmed no statistically significant differences between concentrations obtained by micro-Raman and ISO 19746:2017. In the soil matrix, recoveries ranged between 94 and 101, and the contained biases demonstrate good tolerance to matrix effects. Application to maize plots allowed for monitoring urea disappearance at three depths (0–2 cm, 5–7 cm and 10–15 cm) over 90 days. These differentiated areas of rapid surface hydrolysis from more persistent fractions at depth. The Eco-Scale (96), GAPI (pictogram dominated by green areas), and AGREE (0.88) metrics confirm a significantly lower environmental footprint than that of the chromatographic method. The proposed micro-Raman methodology is emerging as a green, fast, and traceable alternative for monitoring urea in fertilizers and agricultural soils. Full article

To improve the efficiency of CO₂ hydrogenation, it is essential to develop new catalysts as well as new methods of producing them. In our work, we propose a new Fe-, Co-, Cu-containing catalyst preparation technique based on depositing the active component through urea hydrolysis using microwave heating. We also compare catalysts produced with microwave synthesis to samples obtained through traditional synthesis methods, including impregnation and thermal deposition. The obtained catalysts were characterized by XRD, low-temperature N₂ adsorption, SEM., and UV-VIS methods. The catalytic properties of the catalysts depend not only on the nature of the active component, but also on the preparation method. The best results for CO₂ hydrogenation were achieved with Ni-containing catalysts produced by the impregnation method and microwave synthesis. Full article

Fine and ultra-fine sugarcane bagasse (SCB) fractions (≤200 μm) that are naturally generated during industrial grinding have been systematically overlooked in lignocellulosic pretreatment research. Previous studies have largely relied on commercially processed pulps or coarse particles (>200 μm), typically without systematic size fractionation. Here, we demonstrate that these fine fractions—including ultra-fines (≤45 μm), which are often excluded from analytical workflows due to concern about excessive degradation—are viable feedstocks for producing lignin-containing cellulose nanofibers (LCNF) via a sequential thermal hydrolysis treatment (THT)–deep eutectic solvent (DES) pretreatment specifically designed to retain lignin. Size-fractionated SCB (≤45, 45–100, and 100–200 μm) was subjected to THT (190 °C, 15 min), followed by DES treatment using choline chloride/urea (1:2 molar ratio, 130 °C, 2 h). Multi-technique characterization using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) indicated substantial hemicellulose removal (>70%), effective lignin retention (7.6–9.1%), cellulose enrichment (74.0–77.5%), and preservation of cellulose I structure allomorph. The crystallinity index increased from 46.5–52.7% after THT to 56.7–57.2% after DES treatment, and notably, uniform compositional and structural features were obtained across all particle size classes after DES treatment. Subsequent high-pressure microfluidization (700 bar, five passes) yielded LCNF with consistent morphology across all fractions: uniform fibril diameters (24.6–26.2 nm), a discernible lignin coating, and excellent colloidal stability (zeta potential: −86.3 to −95.0 mV). Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) confirmed well-dispersed nanofibrous networks. Collectively, these findings show that the full range of fine SCB fractions can be effectively valorized into high-performance LCNF through sequential THT–DES pretreatment, enabling comprehensive utilization of industrial grinding outputs and advancing circular bioeconomy objectives. Full article

Urease, a metalloenzyme widely present in various organisms, catalyzes the hydrolysis of urea to ammonia and CO₂ and has been extensively utilized in studies and applications of microbially induced calcium carbonate precipitation (MICP). While microbially induced calcium carbonate precipitation (MICP) and silicate mineral bio-weathering are both important biogeochemical processes mediated by microorganisms, and their coupling has been verified in some geological environments, the potential role of urease (a key enzyme in MICP) in mineral weathering remains unreported. In this study, Bacillus velezensis LB002 served as the urease gene donor for the construction of a Bacillus subtilis strain with heterologous overexpression of urease genes. The effects of this engineered strain and the wild-type strain on serpentine weathering and secondary mineral formation were compared. The results showed that the urease activity of the overexpression strain was approximately 3.8 times higher than that of the wild-type strain, and the release of Mg²⁺ during serpentine weathering increased by 17 mg/L. XRD and SEM-EDS analyses revealed that the wild-type strain promoted the formation of vaterite as a secondary mineral, whereas the overexpression strain induced the precipitation of both vaterite and magnesium-containing calcite. These findings demonstrate that urease plays a synergistic role in mineral weathering and that urease overexpression significantly enhances the release of Mg²⁺ from serpentine and the formation of magnesium-containing calcite. Full article

Agro-industrial chestnut waste derived from chestnut processing is usually discharged without further use. However, these residues are attractive due to their high-value composition, rich in sugars and lignin. Among these residues, chestnut burrs (CB) represent a promising feedstock for biorefinery applications aimed at maximizing the valorization of their main constituents. In this study, we propose an environmentally friendly approach based on deep eutectic solvents (DES) formed by choline chloride and urea (ChCl/U) (1:2, mol/mol) for the selective deconstruction of lignocellulosic architecture, followed by enzymatic hydrolysis to release second-generation (2G) fermentable sugars. Pretreatments were applied to raw CB, washed CB (W-CB), and the obtained solid fraction after prehydrolysis (PreH). Structural and morphological modifications, as well as crystallinity induced by DES pretreatment, were characterized using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). Remarkable results in terms of effectiveness and environmental friendliness on saccharification yields were achieved for PreH subjected to DES treatment for 8 h, reaching approximately 60% glucan and 74% xylan conversion under the lower enzyme loading (23 FPU/g) and liquid-to-solid ratio (LSR) of 20:1 studied. This performance significantly reduces DES pretreatment time from 16 h to 8 h at mild conditions (100 °C), lowers the LSR for enzymatic hydrolysis from 30:1 to 20:1, and decreases enzyme loading from 63.5 FPU/g to 23 FPU/g, therefore improving process efficiency and sustainability. Full article

The massive accumulation of agricultural waste, such as wheat straw, and its disposal by burning pose significant environmental challenges. This study explores a sustainable solution by converting wheat straw into composite superabsorbent polymers (SAPs)—superabsorbents contain both synthetic and biodegradable fragments—for improved agricultural water and nutrient management. Wheat straw (WS) was sequentially processed via acid and alkaline hydrolysis to yield fractions with different lignin contents, which were then carboxymethylated (CMWS-Ac and CMWS-Al) to enhance hydrophilicity. These derivatives were incorporated at 20 and 33 wt. %. into SAPs synthesized by copolymerization with acrylamide and acrylic acid. The CMWS-Al-based SAPs exhibited superior properties, including higher equilibrium swelling ratios (up to 566 g/g in water), excellent mechanical strength, and robust gel structure, as confirmed by rheological studies. Furthermore, SAPs demonstrated a significant capacity to retain urea in sand columns, with SAP-CMWS-Al-33 achieving 56% urea retention, highlighting their potential for mitigating fertilizer leaching. The results establish a correlation between the extent of straw processing, the physicochemical properties and lignin content of the derivatives, and the performance of the final SAPs. These wheat straw-based SAPs present a promising, sustainable technology for enhancing soil moisture retention, improving fertilizer use efficiency, and valorizing agricultural waste. Full article

Microbially induced calcium carbonate precipitation (MICP) is recognized as a promising, environmentally sustainable technology with diverse applications in environmental engineering. A bibliometric analysis of 5373 publications indexed in Web of Science from 2005 to 2024 was conducted using CiteSpace and VOSviewer to identify research trends and hotspots in biomineralization and calcium carbonate (CaCO₃) studies. The results showed exponential growth in publications, increasing from 96 in 2004 to 397 in 2024 and spanning 91 interdisciplinary research areas. China, United States of America, and Germany were identified as the leading contributors. Research evolution was categorized into five distinct phases, progressing from initial crystal formation investigations to the current emphasis on underlying microbial mechanisms. Trend analysis revealed four emerging research hotspots: interfaces (0.22), crystal morphology (0.18), amorphous calcium carbonate (0.05), and bacteria (0.02). Mechanisms of MICP across bacteria, fungi, and algae were examined, revealing diverse metabolic pathways, including urea hydrolysis, denitrification, and photosynthesis. These findings suggest a paradigm shift in research toward microbial diversity and the role of extracellular polymeric substances. This shift provides valuable insights for developing sustainable biotechnological applications in environmental remediation. Full article

Compost amendments are widely recognized as an effective strategy for improving soil quality, modulating enzyme activities, and enhancing nitrogen cycling. Urease, a key enzyme in nitrogen transformation, is characterized by kinetic parameters such as the maximum reaction rate (V_max) and Michaelis constant (K_m), as well as thermodynamic attributes including temperature sensitivity (Q₁₀), activation energy (E_a), enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS). However, how different compost sources regulate urease kinetics, thermodynamics, and nitrogen availability remains poorly understood. In this study, we evaluated the effects of three compost amendments—mushroom residue (MR), mushroom residue–straw mixture (MSM), and leaf litter (LL)—on urease kinetics and thermodynamics in a temperate agroecosystem. The MSM treatment significantly enhanced urea hydrolysis capacity and catalytic efficiency. In contrast, LL treatment resulted in the highest Km value, indicating a substantially lower enzyme-substrate affinity. Furthermore, MSM reduced the E_a and increased the thermal stability of urease, thereby supporting enzymatic performance under fluctuating temperatures. Collectively, our findings highlight that compost composition is a critical determinant of urease function and nitrogen turnover. By elucidating the coupled kinetic and thermodynamic responses of urease to compost inputs, this study provides mechanistic insights to guide optimized soil management and sustainable nitrogen utilization in temperate agricultural systems. Full article

Phosphorylated cellulose nanocrystals (P-CNCs) are a superior alternative to conventional sulfuric acid-derived CNCs because of their enhanced thermal and colloidal stability. However, further research is needed to understand the factors influencing their synthesis and properties for advanced material applications. In this study, P-CNCs were synthesized from bleached hardwood kraft pulp (BEKP) using a controlled hydrolysis method involving pretreatment with H₃PO₄ followed by reaction with metaphosphoric acid (HPO₃) and urea. To optimize the process, a full factorial design was employed to evaluate the effects of reaction time (60–90 min) and HPO₃ concentration (3–4 M). The P-CNCs were characterized using physicochemical, morphological, and thermal analyses. Surface charge densities ranged from 757 to 1993 mmol/kg, with exceptional colloidal stability, as evidenced by zeta potentials ranging from −30.17 to −67.40 mV. Statistical analysis showed that reaction time had a significant main effect on surface charge (p-value = 0.0022) and zeta potential (p-value = 0.0448), while a significant interaction between reaction time and HPO₃ concentration was observed when analyzing the surface charge (p-value = 0.0097), suggesting a combined effect of these factors on the surface modification of CNC. Crystallinity indices ranged from 63.6% to 71.3%, and the thermal stability exceeded that of the raw material. These findings contribute to a better understanding of the surface modification and stability of P-CNCs and support efforts to sustainably produce functional CNCs for advanced composite applications. Full article

Optimizing resources to produce higher quality food is key to promoting more resilient agroecosystems. Although the use of biostimulants in agriculture has been gaining importance in recent years, their success depends on edaphoclimatic conditions and on the specific plant species. For this reason, the main aim of this study was to evaluate the effect of biostimulants (amino acids obtained from the enzymatic hydrolysis of plant extracts) on durum wheat yield variables and grain quality (protein content). Five treatments (control treatment—T1, biostimulants—T2, slow-release urea—T3, biostimulants plus slow-release urea—T4, Mg and micronutrients—T5) were tested in a field experiment conducted over 3 seasons in the south of Spain; all were dosed at 120 kg N ha⁻¹. The number of spikes increased significantly with biostimulant treatments in the first season (up to 33%, T2 and T4), while the highest significant grain yields were obtained with biostimulants applied individually in the first season (29.5%-T2) and biostimulants in combination with slow-release urea the second season (27.3%-T4), related to T1. Grain protein concentration was influenced by the treatment only in the second season, the driest during the study, when it was increased with biostimulants up to 4.2% with T2 in comparison with T1. Total protein production increased (28.1%T2) in the first season, (8.1–21.9% for T2–T4) in the second season and (6.5% T4) in the third season, when biostimulants were applied alone or in combination with slow-release urea, respectively. In general, plants treated with Mg and micronutrients produced a lower number of spikes, less yield, and reduced total protein compared to those doses with biostimulants. The application of amino acids as biostimulants was demonstrated to enhance durum wheat yield and total protein production and could be a potential tool for promoting nitrogen use efficiency in semi-arid areas. Full article