Search Results (358)

The ecological rice–eel co-culture system is not only beneficial for enhancing productivity and sustainability in agriculture but also plays a crucial role in promoting environmental health. In the present study, based on the long-term positioning trial of the rice–eel co-culture system that began in 2016 and was sampled in 2023, the effects of reduced nitrogen fertilizer application on soil physico-chemical properties and the bacterial community were investigated. Treatments included a conventional regular fertilization treatment (RT), rice–eel co-culture system regular fertilization (IT), and nitrogen-reduction 10%, 30%, and 50% fertilization treatments (IT90, IT70, and IT50). Our research demonstrated the following: (1) Compared to RT, IT significantly increased soil water-stable macroaggregates (R0.25), mean weight diameter (MWD), geometric mean diameter (GMD), and available phosphorus content, with the increases of 15.66%, 25.49%, 36.00%, and 18.42%, respectively. Among the nitrogen-reduction fertilization treatments, IT90 showed the most significant effect. Compared to IT, IT90 significantly increased R0.25, MWD, GMD, and available nitrogen content, with increases of 4.4%, 7.81%, 8.82%, and 28.89%, respectively. (2) Compared to RT, at the phylum level, the diversity of Chloroflexi was significantly increased under IT and IT50, and the diversity of Gemmatimonadota was significantly increased under IT90, IT70, and IT50. The diversity of Acidobacteriota was significantly higher in IT90 and IT70 compared to IT. It was shown that the rice–eel co-culture system and nitrogen fertilizer reduction could effectively improve the degradation capacity of organic matter and promote soil nitrogen cycling. In addition, redundancy analysis (RDA) identified total phosphorus, total nitrogen, and available nitrogen (p = 0.007) as the three most important environmental factors driving changes in the bacterial community. (3) The functional prediction analysis of soil microbiota showed that, compared to RT, the diversity of pathways related to biosynthesis (carbohydrate biosynthesis and cell structure biosynthesis) and metabolism (L-glutamate and L-glutamine biosynthesis) was significantly higher under IT70, IT90, IT, and IT50 (in descending order). However, the diversity of pathways associated with degradation/utilization/assimilation (secondary metabolite degradation and amine and polyamine degradation) was significantly lower under all the rice–eel co-culture treatments. In conclusion, the rice–eel co-culture system improved soil physicochemical properties and the soil microbial environment compared with conventional planting, and the best soil improvement was achieved with 10% less N fertilizer application. Full article

Lanthanide rare earth elements possess significant promise for material applications owing to their distinctive optical and magnetic characteristics, as well as their versatile coordination capabilities. This study introduced a lanthanide-functionalized magnetic nanocellulose composite (NNC@Fe₃O₄@La(OH)₃) for effective phosphorus/nitrogen (P/N) ligand separation. The hybrid material employs the adaptable coordination geometry and strong affinity for oxygen of La³⁺ ions to show enhanced DNA-binding capacity via multi-site coordination with phosphate backbones and bases. This study utilized cellulose as a carrier, which was modified through carboxylation and amination processes employing deep eutectic solvents (DES) and polyethyleneimine. Magnetic nanoparticles and La(OH)₃ were subsequently incorporated into the cellulose via in situ growth. NNC@Fe₃O₄@La(OH)₃ showed a specific surface area of 36.2 m²·g⁻¹ and a magnetic saturation intensity of 37 emu/g, facilitating the formation of ligands with accessible La³⁺ active sites, hence creating mesoporous interfaces that allow for fast separation. NNC@Fe₃O₄@La(OH)₃ showed a significant affinity for DNA, with adsorption capacities reaching 243 mg/g, mostly due to the multistage coordination binding of La³⁺ to the phosphate groups and bases of DNA. Simultaneously, kinetic experiments indicated that the binding process adhered to a pseudo-secondary kinetic model, predominantly dependent on chemisorption. This study developed a unique rare-earth coordination-driven functional hybrid material, which is highly significant for constructing selective separation platforms for P/N-containing ligands. Full article

We present a theoretical model of the hydrogenation and amination of a primal carbon cluster of the tangled polycyclic type. Hydrogen atoms were introduced via H₂, while the nitrogen source was NH₃. The initial chemical processes were modeled using Born–Oppenheimer Molecular Dynamics. Metadynamics was employed to accelerate the saturation. The reactions were characterized in terms of barriers, topology, and intricate changes in the electronic structure. All transition states were identified. Multiple mechanisms for each type of reaction were discovered. Occasional unbiased changes in the carbon skeleton, induced by the guided processes, were observed. The initial addition reactions had no barriers due to the instability and high reactivity of the carbon structure. The final product of barrierless hydrogen saturation was C₂₅H₂₆. This molecule included multiple isolated double bonds, a medium-sized conjugated π system, and no triple bonds. Ammonia additions resulted in quaternary ammonium groups and primary amino groups. In the subsequent amination, a barrier appeared in fewer steps than in repetitive hydrogenation. The final product of barrierless saturation with NH₃ was C₂₅H₂(NH₃)₂NH₂. Further amination was characterized by a forward free-energy barrier of an order of magnitude larger than the reverse reaction, and the product was found to be unstable. Full article

The safety concerns associated with sensitivity issues regarding long nitrogen chain-based energetic compounds, especially for eight or more catenated nitrogen atoms in backbones, need to be resolved. Incorporating specific functional groups represents a key approach for enhancing stability in organic energetic materials. This study reports the synthesis of 1,1′-(diazene-1,2-diyl)bis(4-nitro-1H-1,2,3-triazole-5-carboxamide) (S8), an N8-chain compound featuring strategically placed amide groups. Employing THA(O-tosylhydroxylamine) and KMnO₄, 1,1′-(diazene-1,2-diyl)bis(4-nitro-1H-1,2,3-triazole-5-carboxamide) (S8) was synthesized and underwent N-amination and oxidative azo coupling. Comprehensive characterization, including X-ray diffraction, mechanical sensitivity testing, and theoretical analysis, alongside comparative studies with known N8 compounds, revealed that S8 exhibits unprecedented stability within its class. Among reported N8-catenated nitrogen chain compounds, attributed to the incorporation of the amide functionality, S8 demonstrates the highest impact sensitivity (IS = 10 J) and friction sensitivity (FS = 40 N) while maintaining excellent detonation performance (D = 8317 ms⁻¹, P = 28.27 GPa). This work highlights the amide group as a critical structural part for achieving high stability in sensitive long-nitrogen-chain energetic materials without compromising performance. Full article

Tomato waste (TW) was employed as a sustainable source for the synthesis of fluorescent carbon dots (CDs) via a microwave-assisted hydrothermal carbonization (Mw-HTC) method, aiming at its valorization. Several amines were used as nitrogen additives to enhance the fluorescence quantum yield (QY) of CDs, and a set of reaction conditions, including additive/TW mass ratio (0.04–0.32), dwell time (15–60 min), and temperature (200–230 °C) of the HTC process, were scrutinized. The structural analysis of the tomato waste carbon dots (TWCDs) was undertaken by FTIR and ¹H NMR techniques, revealing their most relevant features. In solid state, transmission electron microscopy (TEM) analysis showed the presence of nearly spherical nanoparticles with an average lateral size of 8.1 nm. Likewise, the topographical assessment by atomic force microscopy (AFM) also indicated particles’ heights between 3 and 10 nm. Their photophysical properties, revealed by UV–Vis, steady-state, and time-resolved fluorescence spectroscopies, are fully discussed. Higher photoluminescent quantum yields (up to 0.08) were attained when the biomass residues were mixed with organic aliphatic amines during the Mw-HTC process. Emission tunability is a characteristic feature of these CDs, which display an intensity average fluorescence lifetime of 8 ns. The new TWCDs demonstrated good antioxidant properties by the ABTS radical cation method (75% inhibition at TWCDs’ concentration of 5 mg/mL), which proved to be related to the dwell time used in the CDs synthesis. Moreover, the synthesized TWCDs suppressed the growth of Escherichia coli and Staphylococcus aureus at concentrations higher than 2000 μg/mL, encouraging future antibacterial applications. Full article

Nitrogen and sulfur-co-doped carbon dots (N, S-CDs) were synthesized using a simple, eco-friendly hydrothermal technique with L-cysteine as the precursor. The synthesis approach produced highly water-dispersible, heteroatom-doped CDs with surface functional groups comprising amine, carboxyl, thiol, and sulfonic acid. Data analysis of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) confirmed their amorphous nature, nanoscale dimensions (1–8 nm, average particle size of 2.6 nm), and surface chemistry. Optical examination revealed intense and pure blue fluorescence emission under UV excitation, with excitation-dependent emission behavior attributed to surface defects and heteroatom doping. The N, S-CDs were applied as fluorescent probes for detecting perfluorooctanesulfonic acid (PFOS), a notable component of the perfluoroalkyl substances (PFAS) family, demonstrating pronounced and concentration-dependent fluorescence quenching. A linear detection range of 3.33–20 µM and a limit of detection (LOD) of 2 µM were reported using the N, S-CDs probe. UV-Vis spectral shifts and dye-interaction investigations indicated that the sensing mechanism is regulated by non-covalent interactions, primarily electrostatic and hydrophobic forces. These findings confirm the potential of N, S-CDs to be used as effective optical sensors for detecting PFOS in environmental monitoring applications. Full article

Peptoids are peptidomimetics in which the side chain is attached to the nitrogen of the amide group rather than the α-carbon. This alteration in the backbone structure is highly valued because it endows beneficial properties, including enhanced resistance to proteolysis, greater immunogenicity, improved biostability, and superior bioavailability. In this current study, we focused on the Ugi-4CR-based one-pot synthesis of peptoids using 1,4-dithiane-2,5-diol as the carbonyl component together with amine, carboxylic acid, and isocyanides. Four new peptoids—5a, 5b, 5c, and 5d—were designed and efficiently prepared in good chemical yields and were subjected to DFT investigations for their electronic behavior. These compounds have free OH, SH, and terminal triple bonds for further chemistry. In a computational analysis, the spectral data of compounds 5a–5d were juxtaposed with calculated spectral values derived from the B3LYP/6-311G(d,p) level. The electronic excitation and orbital contributions of 5a–5d were predicted using TD-DFT calculations. A natural bond order (NBO) analysis was utilized to investigate the electronic transition of newly synthesized peptoids, focusing on their charge distribution patterns. Furthermore, MEP and NPA analyses were conducted to predict charge distribution in these compounds. The reactivity and stability of the targeted peptoids were evaluated by global reactivity descriptors, which were determined with frontier molecular orbital analysis. The DFT results revealed that compound 5c displayed marginally higher reactivity compared to 5a, 5b, and 5d, possibly due to its extended conjugation. Full article

Traditional meat products are renowned for their distinctive flavor and palatability. Nevertheless, the safety of meat products produced by cottage industries remains a matter of concern, especially regarding the content of biogenic amines (BAs) and overall quality. Currently, limited published data exist on these aspects. This study aimed to assess the levels of BAs and key quality index in 41 traditional meat products sourced from China. The analysis revealed that all samples contained measurable levels of total biogenic amines, with concentrations ranging from 11.76 mg/kg to 1632.24 mg/kg. The nitrite content and total volatile basic nitrogen (TVB-N) value of some samples exceeded the standard and normal range. The findings indicate that BAs levels, TBARS values, and nitrite residues of the tested meat products surpassed toxicity thresholds outlined by various regulatory bodies, emphasizing the critical need for enhanced control measures to mitigate biogenic amine content, TBARS, and nitrite residues in meat products. Full article

Ordered mesoporous carbon materials (OMCMs) are widely used as high-performance electrode materials due to their uniform pore structure, excellent electrical conductivity, and good stability. In this paper, three OMCMs with controllable N content were prepared by a nanocasting method using Fe₃O₄ nanocrystals as the template and organic ligands as the carbon source. By adopting a ligand exchange strategy, oleic acid, oleic amine, and octyl amine were successfully capped onto the Fe₃O₄ nanocrystals, respectively, which allowed the rational control of the elemental composition of OMCMs at the molecular level. Further characterizations revealed that the nitrogen content of the resulting OMCMs increased as the proportion of nitrogen atoms in the ligand increased, while the order of the porous structure decreased as the hydrocarbon chain length decreased. This study demonstrates that both the N-doping content and the order of the OMCMs are influenced by the N-containing ligand. This finding will provide a fundamental aspect for their further applications as high-performance electrode and catalytic materials in the field of electrochemistry. Full article

This study investigates nitrogen metabolism during the middle of the second fermentation in stopped bottles of sparkling wine, focusing on two flor Saccharomyces cerevisiae yeast strains (G1 and N62) isolated from the velum of biologically aged wine. Nitrogen compounds, including amino acids, biogenic amines, and ammonium chloride, were quantified, revealing strain-specific differences in nitrogen utilization and production. Proteomic analysis identified 1053 proteins, with 127 showing significant differences between strains. Strain G1 demonstrated enhanced cell wall remodeling and prioritized nitrogen conservation via arginine and lysine biosynthesis, while strain N62 exhibited increased translational activity and alternative carbon utilization pathways. Notably, strain N62 produced higher concentrations of biogenic amines (putrescine and tyramine), likely due to its greater decarboxylation capacity. Principal Component Analysis (PCA) highlighted clear differentiation in the nitrogen compound profiles across the base wine and wines inoculated with the two strains. The proteome of strain N62 showed increased mitochondrial activity and TCA cycle involvement, facilitating faster fermentation (27 days vs. 52 days for G1), growth (46 × 10⁶ cells/mL vs. 21 × 10⁶ cells/mL for G1) and cell viability (4 × 10⁶ cells/mL vs. 0.7 × 10⁶ cells/mL for G1). These findings suggest that yeast strain selection significantly influences nitrogen metabolism and potentially aroma profiles and and fermentation dynamics in sparkling wine production. Understanding these metabolic adaptations provides valuable insights for optimizing yeast performance to enhance wine quality and preserve regional characteristics. Full article

The objective of the present study was to determine the effect of mixed plant extracts on chemical (pH, total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA), thiobarbituric acid reactive substances (TBARS), biogenic amines, relative fatty acid composition) and microbiological quality indicators of vacuum-packed fish burgers stored at 0 ± 2 °C over 13 days. Three mixtures of common juniper by-product and blackberry leaves extracts (JB), Padina pavonica and prickly juniper needles extracts (PCJ), and blackberry leaves extract with catechin and vanillic (BCV) were tested. At the end of storage, TVB-N (15.38–20.03 mg/100 g) and TMA (10.64–15.63 mg/100 g) of burgers with extracts were significantly lower than those of the control group (22.77 mg TVB-N/100 g, 18.37 mg TMA/100 g). The TBARS values in the control burger reached 2.62 ± 0.02 µmol malondialdehyde (MDA)/100 g, while in burgers with extracts, final values were in the range of 0.62 ± 0.01 to 0.80 ± 0.02 µmol MDA/100 g. The extracts showed no effect on biogenic amine formation (tryptamine, putrescine, and cadaverine levels increased during the storage, being the lowest in BCV) or microbial counts, with the exception of the Pseudomonas sp. counts that were significantly lower in JB and PCJ in comparison to the control, reaching 4.1, 4.1, and 5.0 log CFU/g in JB, PCJ, and control, respectively. Full article

N-nitroso dimethylamine (NDMA), a common nitrogen disinfection by-product and carcinogen, can be removed using rapid sand filtration (RSF) after coagulation; however, its removal mechanism has not been extensively studied. This study analyzed NDMA and the water pollutant parameter removal rate change tendency in the filtrates of simulated supernatants directly and after enhanced coagulation (EC) using composite PAC/PDMDAAC that mimics treated Yangtze River water separated into blank, single-component, and mixed multi-component (MMC) water systems containing NDMA and pollutants like diatomite (DTA), humic acid salt (HAs), dimethyl amine (DMA), and ammonium nitrate (NH₄NO₃). Meanwhile, a correlation analysis of removal rate changes and adsorption analysis using SEM (surface morphology), polar functional groups, and zeta potentials (surface charge) were performed to obtain mechanistic insights into NDMA removal via adsorption. The results revealed that removal rates gradually increased with an increasing volume of filtrates, and there were correlations for NDMA-HAs, NDMA-DMA, NDMA-DTA, and NDMA-NH₄NO₃. The highest NDMA removal rates in the blank system were 10.29% using RSF directly and 12.84% after enhanced coagulation, indicating improved efficiency with coagulation. However, single and mixed systems showed that NDMA removal rate changes were enhanced by water pollutants and coagulation functions. The NDMA removal mechanism was verified, and it was revealed that the level of NDMA adsorption on water pollutants varies based on microstructure, available polar functional groups, and surface charge interactions that are strengthened by coagulation functions for improving the affinity of NDMA and pollutants on the sand surface. These findings provide new insights into NDMA removal mechanisms via adsorption and highlight the role of water pollutants and enhanced coagulation in strengthening rapid sand filtration for NDMA removal. Full article

Polyethylene imine (PEI) is a synthetic water-soluble and nitrogen-rich polymer with an ethylene amine repeating unit. It exists in a linear or branched forms and finds applications in various areas. PEI is often chemically modified by crosslinking reactions using molecular and polymeric crosslinkers (e.g., trichlorotriazine, epichlorohydrin, ethylene glycol diglycidyl ether, poly(ethylene glycol) diglycidyl ether, etc.) to increase its stability and reduce its water solubility. PEI (pristine/crosslinked) has a strong affinity for metal cations (e.g., Cu²⁺, Au³⁺, Pb²⁺, etc.), where the nitrogen atoms interact with the metal ions, and hence is suitable to remove metals from water with high efficiency. A thin film of crosslinked PEI on substrates can be prepared and finds diverse applications such as in removing metals and dyes, and biofouling prevention in the marine environment. The copper ion, as an example, can be stored (adsorbed) in a thin film of crosslinked PEI on a carbon cloth substrate, which can be released to water by passing an electric current through the film or with an acid treatment. It has also been reported that crosslinked PEI and composite materials can be used for the adsorption of dyes and gases such as CO₂ and SO₂ from the environment. The performance of pristine/composite/crosslinked PEI in gas, metal ion, and dye adsorption is affected by several factors. The focus of this review is to discuss the different reactions used to crosslink PEI and review the properties of the crosslinked materials and their applications. Studies have shown that the properties of the crosslinked PEI and hence its success in capturing metal ions, dyes, and CO₂ is dependent not only on the type of crosslinker but also on the degree of crosslinking. Full article

In this study, the real-time shelf life of frozen fillets of two different types of fish, tuna (Thunnus albacares) and hake (Merluccius hubbsi), was studied, simulating a bulk system sale. A glaze treatment was used on all the samples at the beginning, and during the 60-day storage period, the glaze was reapplied at regular intervals on half of the samples (“glazed”), while the other half was not re-glazed (“control”). To assess the quality changes in the two products, the peroxide value (PV), total volatile basic nitrogen (TVB-N), biogenic amines and volatile composition were determined every twenty days. Our results showed that both the glazed and control products did not exceed the legal limits of 35 mg/100 g of TVB-N and 100 mg/kg of histamine. In the hake fillets, in particular, glazing reduced the alteration phenomena associated with oxidative processes. In contrast, because of the high initial thickness of the glazing layer (20% of the weight of the frozen product), the reapplication of glazing during the storage period did not lead to any significant differences between the glazed and control tuna fillets. In conclusion, the different fishes’ compositions affect their conservation after the freezing process, which was improved by means of glazing in the case of the hake fillets. Full article

The main disadvantages of using soybean oil extraction waste as a raw feed material are its high contents of fiber, fat, and anti-nutritional factors. Therefore, several processing methods such as extrusion and hydrolysis are used to overcome these disadvantages and increase the availability of high-quality proteins to animals from this by-product. This study is concerned with the hydrolysis of extruded soybean meal in the presence of bacterial alkaline proteases. The effects of various process parameters were investigated to determine the optimal process parameters for hydrolysis in terms of the total free amino acid and amine nitrogen contents. The experiment included two sets of parameters that were selected for comparison: the temperature and pH in ranges of t 45–50 °C, pH 8–11, compared to the temperature and pH ranges of t = 40–45 °C and pH 7–9, using three enzyme/substrate ratios (1:10, 1:20, and 1:30). The protein hydrolysate was stored for three months after it was treated with two different preservatives (sorbic acid and thymol). Based on the results, it was found that the total free amino acid content was higher when the temperature range was 45–50 °C, the pH range was 8–11, and sorbic acid was used as a preservative. Full article