Molecular Weight Fraction Research Articles

Unraveling the mystery: Extraction and component analysis of irrecoverable foulants of end-of-life membrane from large-scale MBR

Membrane bioreactors (MBRs) are increasingly employed in municipal wastewater treatment, with membranes inevitably reaching their end-of-life (EOL) primarily due to the accumulation of irrecoverable fouling. Nevertheless, the composition and properties of irrecoverable fouling remain ambiguous due to the lack of appropriate extraction and analytical methods. Herein, we developed a temperature-regulated organic solvent extraction method to extract and analyze irrecoverable foulants in EOL ultrafiltration membranes at various locations within a large-scale MBR for municipal wastewater treatment. The irrecoverable foulants encompassed a high molecular weight fraction not observed in the influent, potentially induced by aggregation from organic-inorganic foulant interaction. The terrestrial humic acid (HA)-like substance dominated the organic components of irrecoverable foulants, and the chelating cation Ca emerged as a dominant inorganic compound. Unexpectedly, we noticed the enrichment of Al, Fe, and Si in the irrecoverable fouling, despite their relatively low rejections by the EOL membrane. The potential complex interactions among HA-like substances, Ca, Al, Fe, and Si were revealed by correlation and cluster analysis. The strong bridging potentials of [Al(OH)4]-, Fe(OH)3 at neutral pH, coupled with the colloidal property of Si, may facilitate the aggregation of organic and inorganic compounds, forming complex irrecoverable foulants with strong affinity for the membrane matrix. Besides, the irrecoverable fouling exhibited an increasing trend along the water flow direction. The mystery of irrecoverable fouling of EOL membrane was, for the first time, systematically unraveled, establishing a foundation for the development of effective membrane cleaning and regeneration technology.

Solution properties of laccase-treated pectic polysaccharides derived from steam-dried sugar beet pulp

Steam-drying of sugar beet pulp enables hot water extraction of pectic polysaccharides without adding acid to the extraction medium with a yield higher than the conventional preparation method but a lower molecular weight. The objective of the present study was to investigate the effect of laccase treatment on the molecular weight and solution properties of the pectic polysaccharides derived from steam-dried sugar beet pulp using hot water extraction. The weight average molecular weight and intrinsic viscosity of the pectic polysaccharides increased from 97.1 kDa to 147 kDa and from 0.383 dL/g to 0.525 dL/g due to isopropanol fractionation to remove low molecular weight fractions, respectively, and then to 661 kDa and 0.832 dL/g by the laccase treatment at the highest laccase rate examined, respectively. The intrinsic viscosity values showed a power-law relationship with the molecular weight, the exponent value of which was found to be 0.32 prior to the isopropanol fractionation or 0.38 after the isopropanol fractionation. These values were much lower than that derived theoretically for a random coil (0.5) and closer to that for a sphere (0.33). Compared to the results previously reported for various polysaccharides, the concentration dependence of the specific viscosity in the semi-dilute region was weaker, the critical concentration which is the threshold between dilute and semi-dilute solutions was higher, and the so-called coil overlap parameter was lower. The present results indicate that the pectic polysaccharides examined in this study had highly branched, compact, and spherical molecular structure.

Relating Paramagnetic Properties to Molecular Parameters of Humic Acids Isolated from Permafrost Peatlands in the European Arctic.

Free radicals (FRs) are intermediate participants in the transformation process of soil organic matter, and free radical activity is a fundamental property of humic substances. The aim of this work was to conduct a comparative study of the paramagnetic properties of humic acids (HAs) isolated from Histosols by electron paramagnetic resonance (EPR) spectroscopy. The studied Histosols are found in permafrost peatlands in four natural geographic subzones of the European Arctic (from forest tundra to northern tundra). The results obtained showed that in anaerobic conditions on the peatlands in the tundra zone, the formation of semiquinone-type radicals occurs through the reduction of quinone fragments of HAs and leads to an increase in the concentration of paramagnetic centres within HAs. PCA analysis allowed us to reveal relationships between the properties of the initial raw peat samples, the molecular composition of the isolated HAs, and their paramagnetic parameters. It was found that FR localization occurs predominantly on aromatic fragments of lignin nature, which are confined to the low molecular weight fraction of HAs. The g-factor values of the EPR spectra of HAs indicate the presence of carbon- and oxygen-centred FRs in the HA structure, with a predominance of the latter.

Molecular insights into the bonding mechanisms between selenium and dissolved organic matter

Natural organic matter (NOM) plays a critical role in the mobilization and bioavailability of metals and metalloids in the aquatic environment. Selenium (Se), an environmental contaminant of aquatic systems, has drawn increasing attention over the years. While Se is a vital micronutrient to human beings, animals and plants, excess Se intake may pose serious long-term risks. However, the interaction between Se and dissolved organic matter (DOM) remains relatively unexplored, especially the reaction mechanisms and interactions of specific NOM components of certain molecular weight and the corresponding functional group change. Herein, we report an investigation on the interactions between Se and DOM by focusing on the mass distribution profile change of operationally defined molecular weight fractions of humic acid (HA) and fulvic acid (FA). The results showed that across all molecular weights studied, HA fractions were more prone to enhanced aggregation upon introduction of Se into the system. For FA, the presence of Se species results in aggregation, dissociation, and redox reactions with the first two being the major mechanisms. Total organic carbon analysis (TOC), UV–vis spectroscopy (UV–vis), and Orbitrap MS data showed that [10, 30] kDa MW fraction had the largest aromatic decrease (CRAM-like, lignin-like and tannin-like) upon addition of SeO2 via dissociation as the dominant mechanism. Fourier transform infrared spectroscopy (FT-IR) revealed that Se based bridging or chelation of functional groups from individual DOM components through hydrogen bonding in the form of SeO⋯H and possibly Se⋯H and/or attractive electrostatic interactions lead to aggregated DOM1⋯Se⋯DOM2. It was concluded from two-dimensional correlation analyses of excitation emission matrix (EEM) and FT-IR that the preferred Se-binding follows lipid ➔ peptide ➔ tannin ➔ aromatic functionalities. These results provide new understanding of Se interactions with various NOM components in aquatic environments and provide insight for Se assessing health risk and/or treatment of Se contaminated water.

Exposure and effects of synthetic enhanced oil recovery polymers on the Norwegian Continental Shelf

Synthetic polymers are planned to be used for more efficient oil recovery from offshore oil reservoirs. Using synthetic polymers offshore may lead to these being released into the marine environment through produced water (PW) discharges, thereby causing environmental impacts in the ecosystem. In this study, we assess the impacts of discharging synthetic polymers on the Norwegian Continental Shelf (NCS). We use a numerical model called the Dose-related risk and effects assessment model (DREAM) to simulate discharges of polymers into the sea. DREAM assesses impact in terms of environmental impact factor (EIF) values of individual chemicals present in the PW. Two approaches are used: first, using a standard short-time/small-scale/near-field simulation procedure (50 by 50 km); second, using a non-standard long-term/large-scale/far-field simulation procedure (1200 by 1800 km). For the near-field simulations, the impact is assessed by estimating EIF values resulting from the discharge of 200 and 8000 kilodaltons (kDa) molecular weight fractions of Anionic Polyacrylamide (APAM) from a North Sea oil field. The results show higher EIF values for 8000 kDa compared to 200 kDa APAM. Far-field simulations are used because polymers appear to be resistant to microbial degradation and are thus expected to have long residence times in the sea. An increase in concentrations to harmful levels for aquatic species due to repeated discharges from multiple oilfields is thus possible. The results from the far-field simulations are used to establish relationships between the amount of polymer released annually and the resulting highest values of 100- and 75-percentile concentrations. The results indicate that polymers are not expected to build-up on the NCS and there is a significant margin between the expected polymer concentrations and the lowest concentrations at which toxic effects are observed. The established regression equations can be used to indicate maximum expected concentration values for future release scenarios.

Long-lasting flavor compounds of myrtle and immortelle from ancient Egyptian tombs: A study by analytical pyrolysis

In this work, an approach based on evolved gas analysis-mass spectrometry and double-shot analytical pyrolysis-gas chromatography-mass spectrometry was employed to investigate the low and high molecular weight fractions of two aromatic plants, myrtle and immortelle. The method was used to investigate myrtle and immortelle plants from historical herbaria, as well as archaeological samples from garlands found in ancient Egyptian tombs. Analytical pyrolysis allowed us to characterize both the volatile and non-volatile fractions, by sequentially performing a thermal desorption step and a pyrolysis step on the same sample. Volatile components ascribable to the flavor of myrtle and immortelle were detected in the first-shot chromatograms of all samples. These compounds included mono/sesquiterpenoids such as pinene and eucalyptol, and small phenols such as catechol and syringol. The results show that a portion of the volatile compounds of these plants can remain trapped in the lignocellulosic matrix for long times, and that double-shot Py-GC/MS can provide information on the volatile fraction of even archaeological plant samples.

Fractionated lignin as a polyol in polyurethane fabrication

The main purpose of this paper was to systematically evaluate the effect of lignin, which was fractioned by green solvents into different molecular weights and used as polyol in the production of polyurethane foams (PUF). The results indicated that the foams prepared with the lower molecular weight lignin had uniform and complete pore structure and improved the mechanical strength. However, the higher molecular weight fraction lignin improved the density and thermal stability of the foam more significantly at the expense of inferior mechanical strength and pore structure deficiency. When the substitution degree of lignin in the PUF was 2 %–30 %, 99.13 % of the lowest molecular weight lignin was participated in the reaction to produce PUF, which improved the elongation at break (Eb) and tensile strength (Ts) of PUF to 834 % and 0.90 MPa, respectively. Also, thermal stability and the amount of unreacted lignin in PUF were increased at a higher substitution degree of lignin in PUF.

Effect of molecular weight and its modality on pressure-sensitive adhesives behavior of plant oil-based latexes

Semibatch emulsion polymerization of high oleic soybean oil-based monomer (HO-SBM), 2–ethylhexyl acrylate (2-EHA), and styrene (St) was applied to synthesize pressure-sensitive latex adhesives with up to 40 wt% of plant oil-based content. Ternary latex copolymers with similar chemical composition and broadly different molecular weight distribution (MWD) and modality were synthesized at varying temperatures and the mechanism of free-radical initiation. Conventional thermal initiation with ammonium persulphate at 80 °C and ascorbic acid/tert-butyl hydroperoxide redox system of lower reaction temperature up to 20 °C were employed. Linear, short-chain, and long-chain branched macromolecules are formed due to chain-breaking reactions of HO-SBM (chain transfer on allyl groups) and 2-EHA (inter- and intramolecular chain transfer on the polymer). The dominant effect of chain transfer on allyl group protons and subsequent decrease in molecular weight was observed at higher reaction temperatures, while extensively branched polymer with high molecular weight was obtained at reaction temperature close to 20 °C.The effect of MWD and branching on the PSAs performance of synthesized biobased latexes was studied using loop tack and peel strength and lap shear testing and compared to two commercial PSA tapes as a benchmark. A significant increase in shear strength (up to 0.23 MPa) was observed for latex adhesives due to high molecular weight fractions, maintaining satisfactory level of tack (3–7 N) and peel (3–6 N/in). Broad MWD of the copolymers can be beneficial for providing materials with high shear strength (0.25–0.33 MPA) while preserving the significant level of tack (2–4 N) and peel strength (9–12 N/in) on both glass and steel substrates.

Structural and physicochemical characterization of funoran extracted from Gloiopeltis furcata by different methods

Funoran is a sulfated polysaccharide extracted from the red algal Gloiopeltis species with wide uses in many applications such as thickener and adhesive. This study applied two extraction strategies to obtain funoran from Gloiopeltis furcata with various physicochemical properties. In strategy 1, direct hot water extraction (95 °C for 3 h) yielded two funoran fractions. In strategy 2, algae were purified by cold water before hot water extraction (95 °C for 3 h), resulting in two more fractions. FTIR and NMR measurements showed that all fractions were composed of repeating β-d-galactose-6-sulfate and 3, 6-anhydro-α-l-galactose units as the backbone with small amounts of substituents. The highest molecular weight fractions extracted from both methods were polydisperse with approximately 51 % polysaccharides, 5.2 % protein and less than 1.4 % uronic acid with similar structural compositions of funoran. All funoran fractions in a 1.5 % aqueous solution (w/w) exhibited shear thinning behavior at 20 °C. The fractional difference in strategy 2 was clearly observed in which the high molecular weight formed a highly viscous and cloudy solution with low solubility, while the low molecular weight was highly soluble and formed a clear and transparent solution. Upon cooling, funoran fraction solutions exhibited a steep increase in complex modulus │G*│ indicating the gel formation. On reheating, these gels melted at higher temperatures with significant thermal hysteresis and micro-DSC measurements showed peaks confirming the gelation.

Antibacterial protein fraction derived from Streptomyces fradiae against septicemia infection in Labeorohita: Breakthrough in marine drug discovery

The aquaculture sector continues to be an essential source of food, revenue, nutrition, and a means of subsistence for numerous people globally. Intensive aquaculture in a confined region induces environmental stress in farmed fish, which indirectly increases their vulnerability to many diseases. Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio harveyi are the causative bacterial pathogens for septicemia, the most prevalent and commonly seen illness. Disease outbreaks result in a rise in mortality or a decrease in the quality of the meat, consequently inflicting substantial economic losses to carp production. In contrast, the continual use of antibiotics for infection management has contributed to the proliferation of drug-resistant bacteria in aquatic environments. In this context, marine actinobacteria are emerging as possible sources of new secondary metabolites to combat the problem. Actinobacteria are undoubtedly the most prolific producers of secondary metabolites, and they comprise several commercially and biotechnologically significant species. In this investigation, marine actinobacteria were isolated and evaluated for their antibacterial effectiveness against septicemia pathogens. Effective strains were identified as Nocardiopsis sp., Streptomyces sp., and Pseudonocardia sp. Candidate strains culture filtrates were treated with acetone to precipitate complete proteins. The antibacterial and anti-quorum sensing properties of the crude protein against A. hydrophila MTCC 1739 and P. aeruginosa MTCC 9425 were also examined using the agar well diffusion method. In addition, in vivo investigations of the low molecular weight fraction on Labeorohita demonstrated the fraction's efficacy in reducing septicemia infection. After the 8th day of bathing, fish were found to have recovered.

Unmasking the efficacy of Skipjack Tuna (Katsuwonus Pelamis) dark muscle hydrolyzate in lipid regulation: a promising component for functional food

ABSTRACT To effectively utilize the by-products of skipjack tuna (Katsuwonus Pelamis) for the preparation of peptides with lipid-lowering activity, alkaline proteinase was selected from six commercial proteases to hydrolyze dark muscle. An L16 (54) orthogonal design was employed to optimize the hydrolysis conditions, resulting in the production of a high-peptide-content hydrolyzate named KPHs-AL. This hydrolyzate exhibited the ability to significantly reduce TG content. KPHs-AL also showed higher persuasive pancreatic lipase (PL) and cholesterol esterase (CEase) inhibitory potential than various molecular weight (Mw) fractions and other enzymatic hydrolyzates, with IC50 values of 5.14 and 8.51 mg/mL, respectively. Furthermore, KPHs-AL exerted a combined effect of regulating lipid accumulation in FAA-induced steatosis HepG2 cells, leading to decreased total cholesterol (TC) and total triglyceride (TG). Based on the high binding likelihood and interaction with specific binding sites predicted by Pepsite2, 38 peptide sequences were identified as potential PL and CEase inhibitors. Hence, KPHs-AL holds promise as a beneficial component of functional food and exhibits the potential for anti-obesity effects through the alleviation of lipid accumulation

6-deoxy-6-amino chitosan: a preventative treatment in the tomato/Botrytis cinerea pathosystem.

6-deoxy-6-amino chitosan (aminochitosan) is a water-soluble chitosan derivative with an additional amine group at the C-6 position. This modification has improved aqueous solubility, in vitro antifungal activity and is hypothesized to have enhanced in vivo antifungal activity compared to native chitosan. Gray mold disease in tomatoes is caused by the fungus, Botrytis cinerea, and poses a severe threat both pre- and post-harvest. To investigate the optimal concentration of aminochitosan and its lower molecular weight fractions for antifungal and priming properties in the tomato/B. cinerea pathosystem, different concentrations of aminochitosan were tested in vitro on B. cinerea growth and sporulation and in vivo as a foliar pre-treatment in tomato leaves. The leaves were monitored for photosynthetic changes using multispectral imaging and hydrogen peroxide accumulation using DAB. Despite batch-to-batch variations in aminochitosan, it displayed significantly greater inhibition of B. cinerea in vitro than native chitosan at a minimum concentration of 1 mg/mL. A concentration-dependent increase in the in vitro antifungal activities was observed for radial growth, sporulation, and germination with maximum in vitro inhibition for all the biopolymer batches and lower MW fractions at 2.5 and 5 mg/mL, respectively. However, the inhibition threshold for aminochitosan was identified as 1 mg/mL for spores germinating in vivo, compared to the 2.5 mg/mL threshold in vitro. The pre-treatment of leaves displayed efficacy in priming direct and systemic resistance to B. cinerea infection at 4, 6 and 30 days post-inoculation by maintaining elevated Fv/Fm activity and chlorophyll content due to a stronger and more rapid elicitation of the defense systems at earlier time points. Moreover, these defense systems appear to be ROS-independent at higher concentrations (1 and 2.5 mg/mL). In addition, aminochitosan accumulates in the cell membrane and therefore acts to increase the membrane permeability of cells after foliar spray. These observations corroborate the notion that aminochitosan biopolymers can exert their effects through both direct mechanisms of action and indirect immunostimulatory mechanisms. The contrast between in vitro and in vivo efficacy highlights the bimodal mechanisms of action of aminochitosan and the advantageous role of primed plant defense systems.

Structural properties of the biologically active Dictyosphaerium chlorelloides exopolysaccharide α-d-manno-α-l-rhamno-α-d-(2-O-methyl)-galactan

Structure of biopolymers produced by microalgae plays an important role for their potential biological activity prediction and applications. Previously isolated and well characterized dominant fractions (Dch5-8) from ion-exchange chromatography separation of the biologically active microalga Dictyosphaerium chlorelloides exopolysaccharide (Dch) were pooled and partially acid hydrolyzed. The dominant sugar components in the combined Dch5-8 fraction were Gal and its 2-O-methyl derivative, Rha and Man, all accounting for about 94 mol% of total amount of sugars. Separation of obtained hydrolysate on Bio-Gel P-2 afforded ten fractions. Their main components were identified by NMR. Based on oligosaccharide structures, the repeating unit of the polysaccharide backbone was identified as →2)-α-L-Rhap-(1→4)-2-O-methyl-[3-O-β-D-Galp]-α-D-Galp-(1→ branched by Man. Furthermore, the higher molecular weight fraction contained glucuronorhamnan. NMR data indicate 1,4-linked Rha units in the backbone in α and β configuration, branched at O2 by 2,4-di-O-methyl-β-d-glucuronic acid.

Hydrolytic degradation of poly(lactic acid): Unraveling correlations between temperature and the three phase structures

Hydrolysis significantly influences both the properties and degradability of poly(lactic acid), PLA. This work investigates the hydrolysis kinetics of PLA films as affected by degree of crystallinity and temperatures by considering the three-phase model structures (i.e., mobile amorphous, rigid amorphous, and crystalline). Molecular weight and three-phase fraction analyses were performed during hydrolysis to estimate the kinetic rates using phenomenological models. Results revealed that temperature significantly impacted PLA degradation, with distinct characteristics observed for each of these three phases. Above the glass transition temperature, the hydrolysis rates of PLA were comparable among samples with different crystallinity due to rapid water-induced crystallization of the amorphous phases, coupled with accelerated hydrolysis. In contrast, at below the glass transition temperature, the higher crystallinity sample exhibited a faster hydrolysis rate attributed to the presence of the rigid amorphous fraction. An increase in crystallinity introduced more defects due to limited mobility in the rigid amorphous fraction, influencing hydrolysis. The study provides valuable insights into the crucial relationship between temperature, crystallinity, and hydrolysis kinetics which are expected to be useful for predicting PLA degradation behavior during its intended applications and at its end of life.

Induction of Vesicular Trafficking and JNK-Mediated Apoptotic Signaling in Mononuclear Leukocytes Marks the Immuno-Proteostasis Response to Uremic Proteins

Introduction: Uremic retention solutes have been alleged to induce the apoptotic program of different cell types, including peripheral blood mononuclear leukocytes (PBL), which may contribute to uremic leukopenia and immune dysfunction. Methods: The molecular effects of these solutes were investigated in uremic PBL (u-PBL) and mononuclear cell lines (THP-1 and K562) exposed to the high molecular weight fraction of uremic plasma (u-HMW) prepared by in vitro ultrafiltration with 50 kDa cut-off microconcentrators. Results: u-PBL show reduced cell viability and increased apoptotic death compared to healthy control PBL (c-PBL). u-HMW induce apoptosis both in u-PBL and c-PBL, as well as in mononuclear cell lines, also stimulating cellular H2O2 formation and secretion, IRE1-α-mediated endoplasmic reticulum stress signaling, and JNK/cJun pathway activation. Also, u-HMW induce autophagy in THP-1 monocytes. u-PBL were characterized by the presence in their cellular proteome of the main proteins and carbonylation targets of u-HMW, namely albumin, transferrin, and fibrinogen, and by the increased expression of receptor for advanced glycation end-products, a scavenger receptor with promiscuous ligand binding properties involved in leukocyte activation and endocytosis. Conclusions: Large uremic solutes induce abnormal endocytosis and terminal alteration of cellular proteostasis mechanisms in PBL, including UPR/ER stress response and autophagy, ultimately activating the JNK-mediated apoptotic signaling of these cells. These findings describe the suicidal role of immune cells in facing systemic proteostasis alterations of kidney disease patients, a process that we define as the immuno-proteostasis response of uremia.

Floc aging: Crystallization and improving low molecular weight organic removal in re-coagulation.

Iron coagulants have been used extensively in drinking water treatment. This typically produces substantial quantities of insoluble iron hydrolysis products which interact with natural and anthropogenic organic substances during the coagulation process. Previous studies have shown that the removal of low molecular weight (MW) organics is relatively poor by coagulation, which leads to their presence during disinfection, with the formation of halogenated byproducts, and in treated water supplies as potentially biodegradable material. Currently, there is little knowledge about the changes that occur in the nature of coagulant flocs as they age with time and how such changes affect interactions with organic matter, especially low MW organics. To improve this deficiency, this study has investigated the variation of aged flocs obtained from two commonly used iron salts and their impact on representative organic contaminants, natural organic matter (NOM) and tetracycline antibiotic (TC), in a real surface water. It was found that aging resulted in increasing crystallization of the flocs, which can play a beneficial role in activating persulfate oxidant to remove the representative organics. Furthermore, acidification was also found to further improve the removal of low MW natural organics and tetracycline. In addition, the results showed that the low MW fractions of NOM (<1K Dalton) were substantially removed by the aging flocs. These results are in marked contrast to the poor removal of low MW organic substances by conventional coagulation, with or without added oxidants, and show that aged flocs have a high potential of reuse for re-coagulation and activation of oxidants to reduce low MW organics, and enhance drinking water quality.

A low molecular weight fraction of wheat bran aqueous extract acts as a promoter of fused nanospheres after proteolysis with V8

Protein-rich wheat bran aqueous extract was fractionated by size exclusion chromatography. Each of the chromatographic fractions was hydrolyzed with V8 protease in a reaction medium containing Ca2+. Both the fractions and the hydrolysates were characterized physically and chemically. The objective was to obtain information about which components are involved in the formation of nanoparticles, reported in previous works. Six chromatographic fractions from 0.3 to 102.8 kDa were obtained. The results of chemical characterization, electrophoresis, UV-Vis spectroscopy, and infrared spectroscopy revealed the presence of protein-polysaccharide complexes in four of the fractions. Fused nanospheres at different angles were found by scanning electron microscopy after proteolysis of a 15.1 kDa fraction. It was proposed that such binding could provide sites to form branched nanostructures.

Bioactivity of Fucoidan-Rich Extracts from Fucus vesiculosus against Rotavirus and Foodborne Pathogens.

Marine algae are sources of bioactive components with defensive properties of great value against microbial infections. This study investigated the bioactivity of extracts from brown algae Fucus vesiculosus against rotavirus, the worldwide leading cause of acute gastroenteritis in infants and young children. Moreover, one of the extracts was tested against four foodborne bacteria: Campylobacter jejuni, Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes, and the non-pathogenic: E. coli K12. In vitro tests using MA104 cells revealed that both whole algae extracts and crude fucoidan precipitates neutralized rotavirus in a dose-responsive manner. The maximum neutralization activity was observed when the rotavirus was incubated with 100 μg mL-1 of the hydrochloric acid-obtained crude fucoidan (91.8%), although crude fucoidan extracted using citric acid also demonstrated high values (89.5%) at the same concentration. Furthermore, molecular weight fractionation of extracts decreased their antirotaviral activity and high molecular weight fractions exhibited higher activity compared to those of lower molecular weight. A seaweed extract with high antirotaviral activity was also found to inhibit the growth of C. jejuni, S. Typhimurium, and L. monocytogenes at a concentration of 0.2 mg mL-1. Overall, this study expands the current knowledge regarding the antimicrobial mechanisms of action of extracts from F. vesiculosus.

How weathering might intensify the toxicity of spilled crude oil in marine environments.

Crude oils are highly complex mixtures containing many toxic compounds for organisms. While their level of toxicity in a marine environment depends on many parameters, one of the main factors is their composition. After oil spills, their compositions are significantly changed, so it changes the toxicity. In this study, different weathering processes such as evaporation, photooxidation, and biodegradation were applied to crude oil to understand how composition changed over time and how this affects its toxicity on phytoplankton. In laboratory settings, three distinct water-accommodated fraction samples of crude oil were prepared, unweathered, evaporated, and weathered and were exposed to phytoplankton communities at different dilution levels. After 3days, evaporation reduced the crude oil concentration by 47%, and the concentration of the crude oil affected by photooxidation, biodegradation, and evaporation reduced by 81%. This study also showed that even though the weathering reduced the overall amount of crude oil substantially, its toxicity increased significantly. In the microcosm experiments, 7-day EC50 values of the unweathered oil, the evaporated oil and the weathered oil were 49.07, 21.09, and 7.16µg/L, respectively. Different processes altered the crude oil composition, and weathered crude oil ended up with a higher fraction of high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs). A promising relation between the increasing toxicity and HMW PAH fraction indicates that increasing the fraction of HMW PAHs might be one of the main reasons for the weathering process to cause higher crude oil toxicity. These results could be used as a diagnostic tool to estimate the extent of weathering and toxicity of crude oil after spills.

Sialylation and Sulfation of Anionic Glycoconjugates Are Common in the Extracellular Polymeric Substances of Both Aerobic and Anaerobic Granular Sludges.

Anaerobic and aerobic granular sludge processes are widely applied in wastewater treatment. In these systems, microorganisms grow in dense aggregates due to the production of extracellular polymeric substances (EPS). This study investigates the sialylation and sulfation of anionic glyconconjugates in anaerobic and aerobic granular sludges collected from full-scale wastewater treatment processes. Size exclusion chromatography revealed a wide molecular weight distribution (3.5 to >5500 kDa) of the alkaline-extracted EPS. The high-molecular weight fraction (>5500 kDa), comprising 16.9-27.4% of EPS, was dominant with glycoconjugates. Mass spectrometry analysis and quantification assays identified nonulosonic acids (NulOs, e.g., bacterial sialic acids) and sulfated groups contributing to the negative charge in all EPS fractions. NulOs were predominantly present in the high-molecular weight fraction (47.2-84.3% of all detected NulOs), while sulfated glycoconjugates were distributed across the molecular weight fractions. Microorganisms, closely related to genera found in the granular sludge communities, contained genes responsible for NulO and sulfate group synthesis or transfer. The similar distribution patterns of sialylation and sulfation of the anionic glycoconjugates in the EPS samples indicate that these two glycoconjugate modifications commonly occur in the EPS of aerobic and anaerobic granular sludges.