Molecular Weight Distribution Research Articles

Fingerprint profiling for quality evaluation and the related biological activity analysis of polysaccharides from Liuweizhiji Gegen-Sangshen beverage.

Liuweizhiji Gegen-Sangshen beverage (LGS) is popular in China, which has been used for alleviating alcohol-mediated discomfort and preventing alcoholic liver disease (ALD). This beverage is consisted of six herbal components that are known as functional foods and fruits. LGS is rich in polysaccharides, however, the activity and quality evaluation of LGS-derived polysaccharides remain unexplored. The purpose of this study is thus to establish a comprehensive quality control methodology for the assessment of LGS polysaccharides (LGSP) and to further explore the anti-oxidant, anti-inflammatory as well as prebiotic effect of LGSP. LGSP was extracted, followed by analysis of molecular weight distribution, monosaccharide content and structural characterization via integrating the application of high-performance size exclusion chromatography (HPSEC), 1-phenyl-3-methyl-5-pyrazolone-HPLC (PMP-HPLC), fourier transform infrared spectroscopy (FT-IR) as well as nuclear magnetic resonance spectroscopy (NMR) techniques. The anti-oxidation activity of LGSP was determined by DPPH, ABTS, hydroxyl radical scavenging capacity and total antioxidant capacity. The anti-inflammation of LGSP were assessed on the RAW 264.7 cells. The effect of LGSP on growth of Lactobacillus, Bifidobacterium bifidum and Bifidobacterium adolescentis was evaluated. The results demonstrated that LGSP had two molecular weight distribution peaks, with the average molecular weights of (6.569 ± 0.12) × 104 Da and (4.641 ± 0.30) × 104 Da. LGSP was composed of 8 monosaccharides, with galacturonic acid, glucose rhamnose and galactose representing the highest molar ratios. Homogalacturonic acid (HG) type and rhamnosegalacturonic acid glycans I (RG-I) type and α-1,4-glucan were present in LGSP. LGSP concentration in LGS was 17.94 ± 0.28 mg/mL. Furthermore, fingerprint analysis combined with composition quantification of 10 batches of LGSP demonstrated that there was a high similarity among batches. Notably, LGSP exhibited anti-oxidant effect and inhibited expressions of pro-inflammatory factors (TNF-α and IL-6) in LPS-stimulated RAW 264.7 cells. In addition, LGSP remarkably promoted the proliferation of probiotics Lactobacillus, Bifidobacterium bifidum and Bifidobacterium adolescentis, showing good prebiotic activity. The results of present study would be of help to gain the understanding of structure-activity relationship of LGSP, provide a reference for quality evaluation of bioactive LGSP, and facilitate development of unique health and functional products in the future.

Embedding Bioprinting of Low Viscous, Photopolymerizable Blood-Based Bioinks in a Crystal Self-Healing Transparent Supporting Bath.

Protein-based hydrogels have great potential to be used as bioinks for biofabrication-driven tissue regeneration strategies due to their innate bioactivity. Nevertheless, their use as bioinks in conventional 3D bioprinting is impaired due to their intrinsic low viscosity. Using embedding bioprinting, a liquid bioink is printed within a support that physically holds the patterned filament. Inspired by the recognized microencapsulation technique complex coacervation, crystal self-healing embedding bioprinting (CLADDING) is introduced based on a highly transparent crystal supporting bath. The suitability of distinct classes of gelatins is evaluated (i.e., molecular weight distribution, isoelectric point, and ionic content), as well as the formation of gelatin-gum arabic microparticles as a function of pH, temperature, solvent, and mass ratios. Characterizing and controlling this parametric window resulted in high yields of support bath with ideal self-healing properties for interaction with protein-based bioinks. This support bath achieved transparency, which boosted light permeation within the bath. Bioprinted constructs fully composed of platelet lysates encapsulating a co-culture of human mesenchymal stromal cells and endothelial cells are obtained, demonstrating a high-dense cellular network with excellent cell viability and stability over a month. CLADDING broadens the spectrum of photocrosslinkable materials with extremely low viscosity that can now be bioprinted with sensitive cells without any additional support.

Anthraquinones as organophotoredox catalysts for atom transfer radical polymerization via sequential absorption of visible light

AbstractAnthraquinones have been used as the organophotoredox catalysts to catalyze metal‐free atom transfer radical polymerization (ATRP) under visible light irradiation. Polymers with different molecular weight and molecular weight distribution were obtained under different reaction conditions. The “living”/controlled nature of the polymerization was confirmed by the kinetic study, light on/off experiment and the block copolymer synthesis. The anthraquinones are found to catalyze ATRP via redox mechanism via sequential absorption of visible light. Evidence supported by control experiments showed that the excited anthraquinone radical anion or semiquinone anion generated by photo‐induced single electron reduction or subsequent protonation and further reduction were responsible for the initiation/activation of the polymerization.

Evaluation of the environmental and economic scope of an electrocoagulation process for the treatment of wastewater from the instant coffee industry

AbstractIn this study, an industrial wastewater from instant coffee production was treated by electrocoagulation (EC). The effect of various EC operating parameters, such as electrode type, current density, support electrolyte concentration and stirring velocity, were investigated to determine the optimal operating EC conditions. The scope of electrocoagulation (EC) was assessed, in environmental and economic terms, for the treatment of industrial wastewater originated from the production of instant coffee. The evaluation included the effect of EC operating factors (electrode type, current density, supporting electrolyte concentration and stirring velocity) on Color removal, COD and TOC degradation, toxicity, molecular weight distribution, as well as the total operating cost. The following optimal operating conditions were established through a series of preliminary experiments, a Box-Behnken design of experiments, Response Surface Methodology application, and multi-objective optimization analysis: the pair of Fe (anode)-stainless steel (cathode) electrodes, supporting electrolyte = 1.78 g of NaCl/L; current density = 150 A/m2; electrode gap = 3 mm; stirring velocity = 350 RPM; and pH0 = 4.7 (that of raw industrial effluent). Finally, the kinetic study allowed defining the electrolysis operation time of ca. 180 min required to comply with the maximum permissible discharge limits for the production of instant coffee the discharge of soluble coffee effluents, in terms of COD concentration, established by current Colombian legislation. The EC reached ca. 97% decolorization, as well as 72% and 65% of COD and TOC removal degradation, respectively, with total operating costs of 6.26 USD/m3. This yielded an oxidized (COS = 2.87), biocompatible (BOD5/COD = 0.437) and non-toxic effluent, free of contaminants with molecular weight > 30 kDa. The EC appeared as an effective alternative for the treatment of industrial wastewater from the production of instant coffee within the framework of different Sustainable Development Goals (number 6 (Clean water and sanitation), number 7 (Clean and affordable energy), number 9 (Industry, innovation and infrastructure) and 13 (Climate action)).

Impact of the unimodal molar mass distribution on the mechanical behavior of polymer nanocomposites below the glass transition temperature: A generic, coarse-grained molecular dynamics study

Polymer nanocomposites (PNCs) have shown great potential to meet the ever-growing requirements of modern engineering applications. Nowadays, molecular dynamics (MD) simulations are increasingly employed to complement experimental work and thereby gain a deeper understanding of the complex structure–property relations of PNCs. However, with respect to the thermoplastic’s mechanical behavior, the role of its average molar mass M¯n is rarely addressed, and many MD studies only consider uniform (monodispersed) polymers. Therefore, this contribution investigates the impact that M¯n and the dispersity Đ have on the stiffness and strength of PNCs through coarse-grained MD. To this end, we employed a Kremer–Grest bead–spring model and observed the expected increase in the mechanical performance of the neat polymer for larger M¯n. Our results indicated that the unimodal molar mass distribution does not impact the mechanical behavior in the investigated dispersity range 1.0≤Đ≤1.09. For the PNC, we obtained the same M¯n-dependence and Đ-independence of the mechanical properties over a wide range of filler sizes and contents. This contribution proves that even simple MD models can reproduce the experimentally well researched effect of the molar mass. Hence, this work is an important step in understanding the complex structure–property relations of PNCs, which is essential to unlock their full potential.

Fractionation and refining of pectic oligosaccharides derived from onion skins through continuous feed diafiltration

In this work, a diafiltration-based process was investigated for the recovery of pectic oligosaccharides produced by subcritical water hydrolysis from onion skin waste. Four tubular ceramic membranes from 100 to 1 kDa were selected based on the molecular weight of the different galacturonic acid species present in the onion skin hydrolysate. All these membranes showed high selectivity towards pectic oligosaccharides, with low retention for free galacturonic acid, monosaccharides, organic acids, and other impurities. The 50 and 100 kDa membranes completely retained pectic oligosaccharides with a molecular weight exceeding 80 kDa, accounting for approximately 30 % of the initial pectic oligosaccharides in the hydrolysate. However, the purification rate was significantly slower using the 50 kDa membrane due to the increased cake layer resistance. Furthermore, it was examined a fractionation/purification cascade involving sequential diafiltration stages using 100, 10, and 1 kDa membranes at 25 °C, TMP = 1 bar, and a crossflow velocity of 1.5 m s−1. Approximately 87 % of the initial pectic oligosaccharides were successfully recovered and purified in the retentates, highlighting their potential for diverse applications due to their narrow molecular weight distribution, while phenolic compounds and other valuable low molecular weight molecules were recovered in the final permeate.

Well-defined triphenylamine-containing polymers as hole-transporting layers in solution-processable organic light-emitting diodes via living anionic polymerization

In this study, we conducted anionic polymerization of N-[1,1′-biphenyl]-4-yl-N-(4′-ethenyl[1,1′-biphenyl]-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (A) incorporating a triphenylamine group as a hole-transporting unit using sec-butyllithium and potassium naphthalenide as initiators in tetrahydrofuran at −30 ℃ for 10 min. The resultant poly(A)s exhibited controlled molecular weights (Mn = 20.9−126.3 kg/mol) and narrow molecular weight distributions (Mw/Mn ≤ 1.12). The living nature of the propagating chain end of poly(A) was confirmed by postpolymerization. Additionally, block copolymerization of A with styrene (St) and 2-vinylpyridine (2VP) was performed to assess its relative reactivity. Copolymerization resulted in the precise synthesis of well-defined block copolymers with poly(A) segments. Thermal properties of poly(A) were investigated using thermogravimetric analysis and differential scanning calorimetry. Notably, the thermal annealing of poly(A) film at 230 ℃ for 10 min made it insoluble in toluene, indicating its solvent resistance. Thus, poly(A) was used as the hole-transporting layer (HTL) in solution-processable organic light-emitting diodes (OLEDs). A comparative analysis against a reference device containing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) revealed an enhancement in the performance of the OLED comprising thermally annealed poly(A) as the HTL. These results strongly suggest that poly(A) is a promising HTL material for solution-processable OLEDs.

Three anti-inflammatory polysaccharides from Lonicera japonica Thunb.: Insights into the structure-function relationships

This study demonstrates the feasibility of producing three polysaccharides (neutral LJP-1, acidic LJP-2 and acidic LJP-3) with significant in vitro and in vivo anti-inflammatory activities from the flowers of Lonicera japonica. The three polysaccharides differed in chemical composition, molecular weight distribution, glycosidic linkage pattern, functional groups and morphology. They exhibited excellent protective effects (in a dose-dependent manner) in lipopolysaccharide-injured RAW264.7 macrophages and CuSO4-damaged zebrafish via reducing NO production and inhibiting the overexpressions of inflammation-related transcription factors, inflammatory proteins and cytokines in the NF-κB/MAPK signaling pathways. Their anti-inflammatory effects varied owing to their different molecular characteristics and chemical compositions. Overall, LJP-2 at 400μg/mL was the most effective. LJP-2 consisted mainly of → 5)-α-L-Araf (1→, →4)-α-L-GalpA (1→ and →2)-α-L-Rhap (1→ residues with terminal T-β-D-Glcp. Thus, honeysuckle flowers are good sources of anti-inflammatory polysaccharides, and precise fractionation enables the production of potent anti-inflammatory agents for the development of functional foods and healthcare products.

Dissimilar ferric derisomaltose formulations – In vitro comparisons between an originator and its intended similars

BackgroundThe complex nature of intravenous (IV) iron formulations makes manufacturing and characterising similars challenging. This study examined whether simple in vitro tests can distinguish the high-dose IV iron formulation, Monofer® (ferric derisomaltose [FDI]), from the first intended copies of FDI, Rapifer® (FDI intended similar A [FDIIS-A]) and Tosiron® (FDI intended similar B [FDIIS-B]), approved in India and Pakistan, respectively. Neither intended similar is available in Europe or the United States. MethodsIron content, pH, density, non-volatile residue, carbohydrate content, molecular weight distribution, complex robustness (measured using acid hydrolysis half-life [t½]) and free (dialysable) iron content were examined. Mean results from three batches of FDIIS-A were compared with mean values calculated from three batches of Monofer®. Due to product withdrawal, only one batch of FDIIS-B was available for comparison with Monofer®. ResultsIron content was similar for all formulations (∼100 mg/mL). The chromatograms (obtained using gel permeation chromatography) of FDIIS-A and FDIIS-B differed from that of Monofer®. FDIIS-A was substantially less robust than Monofer® (t½: 15 h versus 40.3 h); t½ for FDIIS-B was not tested. Free iron content was substantially higher in FDIIS-A (0.091 % w/v) and FDIIS-B (1.0 % w/v) versus Monofer® (<0.003 % w/v). Where tested, remaining parameters varied between the formulations (insufficient sample quantities prevented all tests being conducted for all intended similars). For all tests, greater inter-batch variability was seen for FDIIS-A versus Monofer®. ConclusionsSimple in vitro tests demonstrated that, aside from total iron content, the first intended similars of FDI bear little resemblance to their originator drug. It is clear that the efficacy and safety profile of Monofer® cannot be extrapolated to the two intended similars. The results call for increased regulatory scrutiny of intended IV iron similars.

Mesoscale modeling of random chain scission in polyethylene melts

Polyolefins account for more than half of global primary polymer production, however only a small fraction of these polymers are currently being recycled. Fragmentation of polymer chains into shorter chains with a targeted molecular weight distribution with the goal of reusing these fragments in subsequent chemical synthesis can potentially introduce an alternative approach to polyolefins recycling. Herein we develop a mesoscale framework to model degradation of polyethylene melts at a range of high temperatures. We use the dissipative particle dynamics approach with modified segmental repulsive potential to model the process of random scission in melts of linear polymer chains. We characterize the fragmentation process by tracking the time evolution of the distribution of degrees of polymerization of chain fragments. Specifically, we track the weight average and the number average degrees of polymerization and dispersity of polymer fragments as a function of the fraction of bonds broken. Furthermore, we track the number fraction distribution and the weight fraction distribution of polymer fragments with various degrees of polymerization as functions of the fraction of bonds broken for a range of high temperatures. Our results allow one to quantify to what extent the distribution of polymer chain fragments during random scission can be captured by the respective analytical distributions for the range of conversions considered. Understanding the thermal degradation of polyolefins on the mesoscale can result in the development of alternative strategies for recycling a range of thermoplastics.

Controlled polymerization of functional acrylamides by rare-earth aryloxide-based Lewis pairs

A series of amine-bridged bis(phenolate) rare-earth (Sc, Y) aryloxides were synthesized and characterized. These complexes were successfully used for the controlled Lewis pair polymerization (LPP) of functional acrylamides in combination with phosphines, affording a new type of polyacrylamides with predictable molecular weight and low molecular weight distribution. The living nature of this LPP was verified by near-quantitative initiation efficiencies, a linear increase of molecular weight vs monomer-to-initiator ratio and monomer conversion, chain extensions, and the synthesis of well-defined block copolymers. The mechanistic studies were performed through the isolation of a zwitterionic intermediate as well as the end-chain analysis of oligomers, showcasing a rare-earth/phosphine cooperation. Furthermore, the resultant polyacrylamides exhibit outstanding thermal stability and great potential for application in photovoltaic devices.

Fault Tolerant Control of Fuzzy Stochastic Distribution Systems With Packet Dropout and Time Delay

The fault diagnosis (FD) and fault tolerant control (FTC) problem of the fuzzy stochastic distribution system (SDS) over packet dropout and time delay is studied. Firstly, the static model of linear fuzzy logic system that approximates the output PDF and the dynamic model with the multiplicative fault in a fuzzy system are established. The random packet dropout and time delay caused by the network are described in a unified framework, in which the lost data is compensated with the latest data received by the buffer. On this basis, an adaptive observer is devised to estimate the unknown multiplicative fault. The design of sliding mode predictive fault tolerant controller is discussed to ensure that the system still has good tracking performance after the fault occurs. Numerical simulations on a molecular weight distribution control system are supplied to prove the effectiveness of the presented scheme. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The motivation of this paper is to improve the reliability of the fuzzy stochastic distribution system with packet dropout and time delay. This kind of stochastic distribution systems is described by the relationship between the input and the output PDF rather than the normal relationship between the input and the output. When the multiplicative fault occurs in the system, the design of fault diagnosis strategy and fault-tolerant controller becomes an important challenge, especially when the system is subject to packet dropout and time delay. To address the above problems, a new fault diagnosis and fault-tolerant control scheme is proposed, which can accurately estimate the time and size of the fault and obtain the satisfactory fault-tolerant control effect.

Using celluloses to reinforce the optimized alginate film in wet state: Effect of cellulose types and cooking treatment

Alginate (Alg) as co-extruded casing is of interest to the meat industry as replacers for natural sausage casing. However, these studies on the mechanical reinforcement of Alg-based film are still limited in the wet state (e.g. co-extrusion process). In this work, Alg-D with the highest viscosity-average molecular weight (1.12 × 105) was selected from four types of alginates based on the results of the viscosity of Alg solutions and film strength. Next, three celluloses (cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and microfibrillated fiber (MFC)) were added to the Alg-D matrix at different concentrations. SEM showed that the cross section of the Alg-based films became more compact and uniform when the size of celluloses decreased. The tensile test revealed that the strength (TS) of Alg-based films exhibited an initial increase followed by a subsequent drop as the cellulose content rose. The best mechanical strengthening effect was the Alg-CNC film (1.16 MPa), which increased by 93.33 % compared with that of pure Alg. Cooking treatment could further enhance this trend. The opacity increased gradually with the increase of cellulose content, while these films were still transparent enough for food packaging. These findings would have potential applications in food packaging, especially co-extruded sausage casings.

Selenium-enriched yeast, a selenium supplement, improves the rheological properties and processability of dough: From the view of yeast metabolism and gluten alteration

This study investigated the effect mechanism of selenium (Se)-enriched yeast on the rheological properties of dough from the perspective of yeast metabolism and gluten alteration. As the yeast Se content increased, the gas production rate of Se-enriched yeast slowed down, and dough viscoelasticity decreased. The maximum creep of Se-enriched dough increased by 29%, while the final creep increased by 54%, resulting in a softer dough. Non-targeted metabolomics analyses showed that Se inhibited yeast energy metabolism and promoted the synthesis of stress-resistance related components. Glutathione, glycerol, and linoleic acid contributed to the rheological property changes of the dough. The fractions and molecular weight distribution of protein demonstrated that the increase in yeast Se content resulted in the depolymerization of gluten. The intermolecular interactions, fluorescence spectrum and disulfide bond analysis showed that the disruption of intermolecular disulfide bond induced by Se-enriched yeast metabolites played an important role in the depolymerization of gluten.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties.

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

Genome-wide screening and characterization of phospholipase A (PLA)-like genes in sorghum (Sorghum bicolor L.).

The characterisation of PLA genes in the sorghum genome using in-silico methods revealed their essential roles in cellular processes, providing a foundation for further detailed studies. Sorghum bicolor (L.) Moench is the fifth most cultivated crop worldwide, and it is used in many ways, but it has always gained less popularity due to the yield, pest, and environmental constraints. Improving genetic background and developing better varieties is crucial for better sorghum production in semi-arid tropical regions. This study focuses on the phospholipase A (PLA) family within sorghum, comprehensively characterising PLA genes and their expression across different tissues. The investigation identified 32 PLA genes in the sorghum genome, offering insights into their chromosomal localization, molecular weight, isoelectric point, and subcellular distribution through bioinformatics tools. PLA-like family genes are classified into three groups, namely patatin-related phospholipase A (pPLA), phospholipase A1 (PLA1), and phospholipase A2 (PLA2). In-silico chromosome localization studies revealed that these genes are unevenly distributed in the sorghum genome. Cis-motif analysis revealed the presence of several developmental, tissue and hormone-specific elements in the promoter regions of the PLA genes. Expression studies in different tissues such as leaf, root, seedling, mature seed, immature seed, anther, and pollen showed differential expression patterns. Taken together, genome-wide analysis studies of PLA genes provide a better understanding and critical role of this gene family considering the metabolic processes involved in plant growth, defence and stress response.

A Bio-Based Tackifier Synthesized by Room-Temperature Cationic Copolymerization of Isobutene and β-Pinene

Whereas the cationic homopolymerization of β-pinene and isobutene (IB) have been extensively studied, their copolymerization is still very scarce, and the conditions under which copolymerization can occur are limited to extremely low temperatures. Moreover, the application of the copolymer has not been reported. Here, a series of room-temperature copolymerizations of β-pinene and IB, using group 13 compounds as catalysts, were conducted. The copolymerizations yielded a low molecular weight (Mn ~ 103) and a narrow molecular weight distribution (Mw/Mn &lt; 2.0) copolymer, with a satisfactory yield at various comonomer feeds, and their glass transition temperature was predictable from the comonomer composition. Furthermore, the tackifying property of the obtained copolymer was investigated using a 180° peel adhesion test. A blend polymer of the copolymer and a styrene-isoprene triblock copolymer showed a high peeling force (0.58 ± 0.14 N/10 mm) and a glass transition temperature low enough for its application as a pressure-sensitive adhesive.

A comparative study of the cell wall level delignification behaviour of four Nordic hardwoods during kraft pulping

Abstract Wood is a heterogeneous material with significant variation among species. This inherent complexity poses a challenge to the continuous expansion of our understanding of the kraft process; yet previous pulping research has mainly been limited to a few species. This study investigates variations among some less studied species and their cell wall level delignification behaviour during kraft pulping. Ground wood of birch, beech, aspen, and alder were pulped at near-constant composition and temperature conditions. Minor, yet significant, differences in the rates of their delignification were observed: aspen had a pronounced fast rate during the initial stage, whereas alder delignified more slowly relative to its high initial lignin content. The dissolution of xylan was substantially faster for birch. In contrast, no substantial differences were detected between the species in the molecular weight and structure of the dissolved wood components, suggesting that the different delignification behaviours stem from variations in the residual phase. The molecular weight distribution of dissolved lignin was uniform during the initial stage of pulping, which is indicative of rapid and extensive fragmentation. Subsequently, the weight increased continuously for the remainder of the process, suggesting that the mass transfer within the cell wall influenced the overall delignification kinetics.

Molecular Weight Distribution of Humic Acids Isolated from Calcic Cryosol in Central Yakutia, Russia.

The transition of soils into fallow state has a significant impact on the accumulation and transformation of soil organic matter (SOM). However, the issue of SOM transformation as a result of soil transition to fallow state in cryolithozone conditions is insufficiently studied. The aim of this study is to investigate the molecular weight (MW) distribution of humic acids (HAs) isolated from soils of central Yakutia. Native, fallow and agricultural soils in the vicinity of Yakutsk city were studied. MW distributions of HA preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersam Biosciences, Uppsala, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10-600 kDa). The data on the molecular-mass distribution of HAs of fallow and agricultural soils of Central Yakutia were obtained for the first time. According to the obtained data, it was found that the highest carbon content in the structure of HAs was observed in agricultural soils (52.56%), and is associated with soil cultivation and fertilizer application. Among the HAs of fallow soils, we note that those soils that are in the process of self-vegetation have a relatively high carbon content in the HAs (45.84%), but the highest content was observed in fallow soils used as hayfields (49.98%), indicating that the reinvolvement of agriculture in fallow soils leads to an increase in the carbon content of HAs. According to the data of the MW distribution of HAs, it was found that the highest content of a high MW fraction of HAs was recorded in native soil (18.8%); this is due to the early stages of humification and the low maturity of organic matter. The highest content of a low MW fraction of HAs was recorded in agricultural soil (73.3%); this is due to the formation of molecular complexes of a "secondary" nature, which are more stable in the environment than the primary transformation products of humification precursors. The molecular composition of the HAs of fallow soils in the process of self-overgrowing is characterized by values closer to the HAs of native soils, which indicates their transformation towards HAs of native soils. The obtained results indicate that the reinvolvement of fallow soils leads to the transformation of the molecular composition of HAs towards HAs of agricultural soils, and to an increase in the resistance of SOM to biodegradation.

Molecular-level insights into dissolved organic matter and its variations of the full-scale processes in a typical petrochemical wastewater treatment plant

Petrochemical wastewater (PCWW) treatment poses challenges due to its unique and complex dissolved organic matter (DOM) composition, originating from various industrial processes. Despite the addition of advanced treatment units in PCWW treatment plants to meet discharge standards, the mechanisms of molecular-level sights into DOM reactivity of the upgraded full-scale processes including multiple biological treatments and advanced treatment remain unclear. Herein, we employ water quality indexes, spectra, molecular weight (MW) distribution, and Fourier transform ion cyclotron resonance mass spectrometry to systematically characterize DOM in a typical PCWW treatment plant including influent, micro-oxygen hydrolysis acidification (MOHA), anaerobic/oxic (AO), and micro-flocculation sand filtration–catalytic ozonation (MFSF–CO). Influent DOM is dominated by tryptophan-like and soluble microbial products with MW fractions 〈 1 kDa and 〉 100 kDa, and CHO with lignin and aliphatic/protein structures. MOHA effectively degrades macromolecular CHO (10.86 %) and CHON (5.24 %) compounds via deamination and nitrogen reduction, while AO removes CHOS compounds with MW < 10 kDa by desulfurization, revealing distinct DOM conversion mechanisms. MFSF–CO transforms unsaturated components to less aromatic and more saturated DOM through oxygen addition reactions and shows high CHOS and CHONS reactivity via desulfurization and deamination reactions, respectively. Moreover, the correlation among multiple parameters suggests UV254 combined with AImod as a simple monitoring indicator of DOM to access the chemical composition. The study provides molecular-level insights into DOM for the contribution to the improvement and optimization of the upgraded processes in PCWW.