Weight Of Polymer Research Articles

Polymerization-Induced Self-Assembly for the Synthesis of Polyisoprene-Polystyrene Block and Random Copolymers: Towards High Molecular Weight and Conversion.

In this study, reversible addition-fragmentation chain- transfer (RAFT) polymerization combined with the polymerization-induced self-assembly (PISA) technique is used to synthesize polyisoprene (PI)-based block and random copolymers with polystyrene (PS), aiming for high molecular weight and monomer conversion. The focus is to optimize the polymerization conditions to overcome the existing challenge of cross-linking and Diels-Alder reactions during the polymerization of isoprene, which typically constrain the reaction conversion and molecular weight of the final polymers. Using a poly(methacrylic acid) (PMAA) macroRAFT agent synthesized in ethanol at 80°C, random and block copolymers of PS-PI with a target molecular weight of 50000gmole-1 and a high monomer conversion of ≈80% are achieved under optimized conditions in water-emulsion at 35°C. 1H nuclear magnetic resonance (NMR) verified the successful synthesis as well as the high content of 1,4 microstructure in polyisoprene. The thermal analysis via differential scanning calorimetry indicated distinct glass transitions for the microphase-separated PI-PS block copolymer, while a single transition for PI-PS random copolymer, indicating no microphase separation. Furthermore, dynamic light scattering analysis together with transmission electron microscopy provided further insight into the self-assembled emulsion nanoparticles of the polymers indicating a particle size in the range 70 to 130nm.

Insight into the Coextrusion Mechanism between Whey Protein Isolate and Cysteine.

The disulfide cross-linking sites of whey protein isolate (WPI) coextruded with dissolved cysteine (Cys) at concentrations of 0, 20, 40, 60, 80, and 100 mM were analyzed by liquid chromatography electrospray ionization tandem mass spectrometry (LC/MS/MS) combined with pLink software, and the structure and gel water distribution of WPI during coextrusion (≤50 °C) were also investigated. LC/MS/MS demonstrated that α-La (6) and α-La (120) were the most active sites for intermolecular disulfide cross-linking of α-La. Meanwhile, the molecular weight of protein polymers in coextruded WPI-Cys was the largest at 100 mM Cys, and α-lactalbumin was the main reactant for polymerization from the result of SDS-PAGE and size exclusion chromatography. Additionally, the high concentration of Cys caused the secondary structure of WPI to gradually change from a highly ordered to a disordered structure during coextrusion. In addition, with an increasing concentration of Cys, the free sulfhydryl group of proteins and the binding force to immobilized water gradually increased. Therefore, this work revealed the disulfide cross-linking mechanism between WPI and Cys under low-temperature coextrusion at the molecular level, and the obtained coextruded cross-linked WPI could serve as a novel food ingredient with excellent water-holding capacity for the food industry.

An Overview of Microorganisms Immobilized in a Gel Structure for the Production of Precursors, Antibiotics, and Valuable Products.

Using free microorganisms for industrial processes has some limitations, such as the extensive consumption of substrates for growth, significant sensitivity to the microenvironment, and the necessity of separation from the product and, therefore, the cyclic process. It is widely acknowledged that confining or immobilizing cells in a matrix or support structure enhances enzyme stability, facilitates recycling, enhances rheological resilience, lowers bioprocess costs, and serves as a fundamental prerequisite for large-scale applications. This report summarizes the various cell immobilization methods, including several synthetic (polyvinylalcohol, polyethylenimine, polyacrylates, and Eudragit) and natural (gelatin, chitosan, alginate, cellulose, agar-agar, carboxymethylcellulose, and other polysaccharides) polymeric materials in the form of thin films, hydrogels, and cryogels. Advancements in the production of well-known antibiotics like penicillin and cephalosporin by various strains were discussed. Additionally, we highlighted cutting-edge research related to strain producers of peptide-based antibiotics (polymyxin B, Subtilin, Tyrothricin, varigomycin, gramicidin S, friulimicin, and bacteriocin), glusoseamines, and polyene derivatives. Crosslinking agents, especially covalent linkers, significantly affect the activity and stability of biocatalysts (penicillin G acylase, penicillinase, deacetoxycephalosporinase, L-asparaginase, β-glucosidase, Xylanase, and urease). The molecular weight of polymers is an important parameter influencing oxygen and nutrient diffusion, the kinetics of hydrogel formation, rigidity, rheology, elastic moduli, and other mechanical properties crucial for long-term utilization. A comparison of stability and enzymatic activity between immobilized enzymes and their free native counterparts was explored. The discussion was not limited to recent advancements in the biopharmaceutical field, such as microorganism or enzyme immobilization, but also extended to methods used in sensor and biosensor applications. In this study, we present data on the advantages of cell and enzyme immobilization over microorganism (bacteria and fungi) suspension states to produce various bioproducts and metabolites-such as antibiotics, enzymes, and precursors-and determine the efficiency of immobilization processes and the optimal conditions and process parameters to maximize the yield of the target products.

Development and characterization of nitazoxanide-loaded poly(ε-caprolactone) membrane for GTR/GBR applications

ObjectiveGuided tissue/guided bone regeneration (GTR/GBR) membranes are widely used for periodontal bone regeneration, but their success depends on a bacteria-free environment. Systemic antibiotic treatment often proves inadequate, moreover, the increasing prevalence of antibiotic resistance in oral infections exacerbates this challenge. This study aimed to fabricate antibacterial membranes using a new class of antibiotics for local drug delivery, to eradicate infections and promote tissue regeneration. MethodsMembranes loaded with nitazoxanide (NTZ) were fabricated via electrospinning using poly(ε-caprolactone) (PCL) with varying concentrations of NTZ (0 %, 2.5 %, and 5 % w/w) relative to the polymer weight. Morphochemical of NTZ-loaded membranes were assessed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier Transform Infrared spectroscopy (FTIR). Mechanical properties were evaluated using universal testing machine and NTZ release profile from membranes was determined by spectrophotometer (λmax = 444) for 14 days. Antimicrobial efficacy against periodontal pathogens, cell compatibility and mineralization were evaluated using periodontal ligament stem cells (PDLSCs). ResultsOptimized spinning parameter maintained a uniform fiber diameter and successful loading of NTZ was confirmed by SEM-EDS and FTIR. NTZ incorporation did not significantly affect mechanical properties, whereas the drug release kinetics showed an initial burst, followed by sustained release over 14 days. NTZ-loaded membranes demonstrated antibacterial activity against Aggregatibacter actinomycetemcomitans (Aa) and Fusobacterium nucleatum (Fn). Importantly, the presence of NTZ showed minimal cell toxicity; however, it reduced the mineralization potential compared with that of the pure PCL membrane, which increased over time. SignificanceTaken together, these findings established that NTZ-loaded membranes could be promising barrier membrane to counteract microbial environment and aid periodontal bone regeneration.

Internally-crosslinked alginate dialdehyde/alginate/gelatin-based hydrogels as bioprinting inks for prospective cardiac tissue engineering applications

Cardiovascular diseases represent a worldwide social and economic challenge, due to heart tissue limited regenerative capabilities. 3D bioprinted cell-laden constructs are a promising approach to develop patches for cardiac regeneration or in vitro models for new drug preclinical discovery and validation. However, the development of bioinks with optimal mechanical, rheological, and biological properties is still a challenge. Although alginate (Alg)-based bioinks have been extensively explored, such hydrogels lack cell adhesion properties and degradability. Additionally, 3D Alg structures are usually obtained by micro-extrusion bioprinting exploiting conventional external cross-linking methods, which introduce inhomogeneities and unpredictability in construct formation. This work exploits Alg internal ionic gelation mechanism to obtain homogeneous self-standing multilayered 3D printed constructs without employing support baths or post-printing crosslinking treatments, combining an insoluble calcium salt (calcium carbonate, CaCO3) with an acidifying agent (D-(+)-Glucono-1,5-lactone, GDL) to promote controlled release of calcium ions. Alg was blended with oxidized alginate (ADA) and gelatin (Gel) to achieve degradable and cell adhesive hydrogels for cardiac tissue engineering. Firstly, ADA/Alg bioink composition was tailored by varying polymer weight ratio (keeping ADA as the main component) and calcium ions concentration to achieve cardiac tissue-like viscoelastic properties. Then, the amount of Gel in ADA/Alg hydrogels was optimized to support adult human cardiac fibroblasts (AHCFs) adhesion, producing shear thinning inks with tunable viscoelastic properties (G’ 650-1300 Pa) and degradation profile (40-80% weight loss after 21 days in phosphate buffered saline, PBS) by varying Gel concentration. ADA/Alg/Gel hydrogels showed a shear thinning behavior suitable for 3D bioprinting and dependent on ink stabilization time, due to the gradual pH-triggered release of calcium ions over time. AHCFs-laden ADA/Alg/Gel bioinks could be successfully printed producing scaffolds with high shape fidelity and good cell viability post-printing. Finally, 3D AHCF-laden and H9C2-laden ADA/Alg/Gel bioinks with the highest gelatin content (25% w/w) allowed cell adhesion after 24 hours of incubation, showing potential application for cardiac tissue modelling. This research presented a comprehensive framework for advancing the design of bioink formulations enabling the printing of cell-adhesive and self-supporting constructs.

Gelatin methacryloyl biomaterials and strategies for trophoblast research

Rising maternal mortality rates in the U.S. are a significant public health issue that must be addressed; however, much of the basic science information required to target pregnancy-related pathologies have not yet been defined. Placental and blastocyst implantation research are challenging to perform in humans because of the early time frame of these processes in pregnancy and limited access to first trimester tissues. As a result, there is a critical need to develop model systems capable of studying these processes in increasing mechanistic detail. With the recent passing of the FDA Modernization Act 2.0 and advances in tissue engineering methods, three-dimensional microphysiological model systems offer an exciting opportunity to model early stages of placentation. Here, we detail the synthesis, characterization, and application of gelatin methacryloyl (GelMA) hydrogel platforms for studying trophoblast behavior in three-dimensional hydrogel systems. Photopolymerization strategies to fabricate GelMA hydrogels render the hydrogels homogeneous in terms of structure and stable under physiological temperatures, allowing for rigorous fabrication of reproducible hydrogel variants. Unlike other natural polymers that have minimal opportunity to tune their properties, GelMA hydrogel properties can be tuned across many axes of variation, including polymer degree of functionalization, gelatin bloom strength, light exposure time and intensity, polymer weight percent, photoinitiator concentration, and physical geometry. In this work, we aim to inspire and instruct the field to utilize GelMA biomaterial strategies for future placental research. With enhanced microphysiological models of pregnancy, we can now generate the basic science information required to address problems in pregnancy.

On the rheological properties of Silica – Poly(ethylene-oxide) dispersions: "Shake-gels" II The effect of silica concentration and molecular weight of polymer

Using rheological techniques, the effect of silica concentration and polyethylene oxide molecular weight has been investigated to follow the gelation/shear thickening behaviour of PEO silica water mixtures, a phenomenon which has become known as "shake gels”. By monitoring the viscosity as a function of the shear rate it was observed that at a critical shear rate the viscosity increased by many orders of magnitude. The higher the silica concentration and the higher the polymer molecular weight the lower the shear rate required for the gel to form. Once formed by dropping the shear rate to a low value or by monitoring the viscoelastic moduli the relaxation of the gel back into the liquid state could be followed. It was noted that the lower the polymer molecular weight or the lower the silica concentration the faster the relaxation process was. It is postulated that the silica particles effectively cross link the gel so that the more silica particles per polymer molecule would result in slower relaxation. Conversely in the gel formation stage the more silica particles per polymer the faster the gel forms are a consequence of the ease by which the silica particles can cross link to form the gel.

Relaxation and entropy generation in dewetting thin glassy polymer films trapped far from equilibrium

AbstractPolymers when confined to a dimension comparable to the length scale of polymer chain coils such as thin films, often lead to molecular relaxation processes distinct from their bulk counterpart. Often observed as thermal and mechanical responses such relaxation has been frequently associated with the squeezing of polymer chains having conformations trapped far from thermodynamic equilibrium and subsequently generating processing‐induced molecular recoiling stress. Relaxation in polymer films can be modified by tuning the molecular recoiling stress, which is directly influenced by the preparation conditions of the polymer thin films. Hence a comprehensive understanding of the genesis and relaxation of molecular recoiling stress becomes necessary. Here, we provide insights into the nonequilibrium nature observed in polymer thin films, focusing majorly on the investigations into the molecular recoiling stress using the dewetting technique. The impact of various factors like temperature of dewetting, thickness of films, molecular weight of polymers, and physical aging affecting the relaxation of molecular recoiling stress is discussed. In addition, discussions on the possible mechanisms of relaxation and modification of molecular recoiling stress by varying the spin‐coating speed and addition of plasticizers are also provided. An alternate approach which gives a new perspective into the relaxation of molecular recoiling stress considering the entropy generated during the dewetting of polymer films is also included. The present work is expected to give the reader a comprehensive understanding of the characteristics of molecular recoiling stress relaxation occurring in polymer thin films.

Molecular dynamics simulation of salt diffusion in constituting phosphazene-based polymer electrolyte

A growing demand to visualize polymer models in liquid poses a computational challenge in molecular dynamics (MD) simulation, as this requires emerging models under suitable force fields (FFs) to capture the underlying molecular behaviour accurately. In our present study, we have employed TIP3P potential on water and all atomistic optimized potentials for liquid simulations FFs to study the liquid electrolyte behavior of phosphazene-based polymer by considering its potential use in lithium-ion polymer batteries. We have explored the polymer's local structure, chain packing, wettability, and hydrophobic tendencies against the silicon surface using a combination of a pseudocontinuum model in MD simulation, and surface-sensitive sum frequency generation (SFG) vibrational spectroscopy. The finding yields invaluable insights into the molecular architecture of phosphazene. This approach identifies the importance of hydrophobic interactions with air and hydrophilic units with water molecules in understanding the behavior and properties of phosphazene-based polymers at interfaces, contributing to its advancements in materials science. The MD study uniquely captures traces of the polymer-ion linkage, which is observed to become more pronounced with the increase in polymer weight fraction. The theoretical observation of this linkage's influence on lithium-ion diffusion motion offers valuable insights into the fundamental physics governing the behavior of atoms and molecules within phosphazene-based polymer electrolytes in aqueous environments. Further these predictions are corroborated in the molecular-level depiction at the air-aqueous interface, as evidenced from the OH-oscillator strength variation measured by the SFG spectroscopy.The fundamental findings from this study open new avenues for utilizing MD simulation as a versatile methodology to gain profound insights into intermolecular interactions of polymer. It could be useful in the application of biomedical and energy-related research, such as polymer lithium-ion batteries, fuel cells, and organic solar cells.

Tailoring the stress-free two-way shape memory effect in sol–gel crosslinked poly(ϵ-caprolactone)-based semicrystalline networks

Two-way shape memory polymers are stimulus-responsive materials capable of changing their shape between two configurations based on an on/off thermal stimulus. While the traditional effect has been studied under the application of an external mechanical load, it was demonstrated also in the absence of an external load. Such a response only relies on a carefully tailored macromolecular architecture of the polymer combined with a specific thermo-mechanical protocol. In particular, semicrystalline networks, either consisting of a multi-phase copolymer network or a homopolymer based network with broad phase transitions, have been proposed to this aim under ad hoc thermo-mechanical histories. In this work, the two-way shape memory behavior is studied on a poly(ϵ-caprolactone)-based network, crosslinked by means of a sol–gel approach and tailored on the selection of the molecular weight of the precursor polymer. Changing the prepolymer precursor allowed to tune the melting/crystallization regions of the networks, thus the thermal region of the reversible shape memory effect. The application of properly designed thermo-mechanical cycles allowed to study the two-way shape memory effect without the application of an external load under tensile conditions. Given a specific network, the stress-free actuation of the reversible elongation-contraction cycle under tensile conditions was induced across its specific melting/crystallization region. The extent of the effect was found to depend on the crystalline fraction remaining for the given actuation temperature and on the tensile stretched state imposed on the materials during the training step. The results were compared with the response achieved under the traditional two-way shape memory protocol under stress. The stress-free two-way shape memory effect was also successfully demonstrated and emphasized, under flexural conditions, which suggests the potential of these materials as intrinsically reversible actuators, promising for applications in the biomedical field and/or for soft robotics.

Effect of polymer weight on the Fischer-Tropsch Synthesis kinetics over the Iron oxide /paraffin/polymer systems as nanocatalysts

Effect of polymer weight on the Fischer-Tropsch Synthesis kinetics over the Iron oxide /paraffin/polymer systems as nanocatalysts

Temperature-sensitive fragrance-releasing polymeric microcapsules

This research aimed to control release of fragrance using thermally-actuated microcapsules so that the release rate shows a considerable change at a certain temperature. Accordingly, four different polymers, namely, two grades of poly(methyl methacrylate) having different molecular weight as well as two poly[(methyl methacrylate)–co-(2-ethylhexyl acrylate)] copolymers, which were synthesized in this work, were designated as capsules’ shell. Number-average molecular weight of the copolymers and one of the two used PMMA grades was in the range of 47 to 56 kDa while that of the other PMMA grade was 344 kDa. Furthermore, Tg of the lower molecular weight grade PMMA and the two copolymers was determined as 119.3, 72.2 and 66.3 °C, respectively, using DSC experiments. Subsequently, R-Limonene as a model fragrance, was encapsulated by either of the polymers using solvent evaporation method. Effect of various parameters, including molecular weight and Tg of the shell polymer and concentration of emulsifier, on morphological characteristics of the microcapsules were investigated. Using two microscopic techniques, it was observed that increment of molecular weight of shell polymer enhances microcapsules’ size, shell thickness and porosity. Moreover, elevation of emulsifier concentration to a certain value of 1.5 wt% was shown to lessen size and porosity of microcapsules. The fragrance release profiles were determined and fitted to several mathematical models, proving that at least one more mechanism, in addition to diffusion, is involved in the release, which was attributed to capillary effects in the shell pores. Moreover, a pronounced increase in release rate upon elevation of temperature from 5 to 15 °C was observed for either of the copolymer shells. The effect was ascribed to remarkable strengthening of segmental mobility of the copolymers due to elevation of temperature and can be regarded as a promising way for the fabrication of smart microcapsules capable of thermal controlling fragrance release.

Studies on adsorptive dehydration of pasteurised milk by filled polymeric IPN hydrogel

ABSTRACT Adsorptive dehydration utilising polymeric hydrogels presents an effective technique for removing excess water from pasteurised milk. This study investigated three Interpenetrating Polymeric Network (IPN) hydrogels comprising Polyvinyl Alcohol (PVOH) and Hydroxyethyl Cellulose (HEC) at mass ratios of 90:10, 70:30 and 50:50, respectively, with Maleic Anhydride (MAn) as a cross-linker at concentrations of 2% 4%, and 8% based on total polymer weight. It was observed that the rate of dehydration increased with higher HEC content in the hydrogels. However, the stability decreased due to changes in the structural alignment of polymer chains and weak cross-linking. Among the tested hydrogels, the one with a composition of 70:30 for PVOH and HEC, respectively, cross-linked with 8% MAn (0.096gm), exhibited the best adsorption (569% Swelling) with minimal changes in pH (<10%) and conductivity (<10%) and was, therefore, selected for further study. This selected hydrogel composition was further enhanced by incorporating a hydrophilic nanofiller (Bentonite) at proportions of 2%, 4% and 6% based on total polymer weight during hydrogel synthesis. The hydrogel with 4% nanofiller (0.081 gm) showed the best results in terms of swelling and stability although the 6% filled hydrogel exhibited superior swelling but lower stability. Finally, the dehydration process was optimised using Type 1 fuzzy logic (T1FL), achieving an R2 value of 95.13%.

The New Methods for Characterization of Molecular Weight of Supramolecular Polymers

The New Methods for Characterization of Molecular Weight of Supramolecular Polymers

Properties of AlCl3 guanidine deep eutectic solvent with addition of polyethylene oxide of different molecular weights supported by quantum-chemical calculation

Deep eutectic solvent of AlCl3 with guanidine HCl was synthesized in the molar ratio 3:1 in the presence of polyethylene glycols of various molecular weights from 1500 to 5·106 g/mol. Concentration of polymer was 2.5 %, 5 % and 10 %. Temperature dependence between 25 and 70 °C of conductivity of each electrolyte was calculated from the cyclic voltammetry of aluminum deposition-stripping measurements. It was found that conductivity increases with molecular weight of polymer in the interval between 2 and 10 kD. This result was interpreted as binding of AlCl3 guanidine to two different sites which have hydroxyl (chain ends) and ether (middle chain) oxygen with relatively higher and lower binding energy respectively. Polymer with longer chain has more low energy binding sites which causes lesser binding and consequently higher conductivity of electrolyte. B3LYP-D3 and DLPNO-CCSD(T) computations support experimental results. DES are discussed in terms of Pearson HSAB principle.

Lactic acid and hydroxyl terminated polybutadiene assisted synthesis of vegetable oil based polyurethanes for sustained drug delivery systems

The present research aims to develop a series of biodegradable, sustainable and biocompatible, polyurethanes (PU–S1 to PU-S4). The synthesis of these polyurethanes involved a combination of different ratios of an epoxidized polyol (followed by ring opening with ethanol) extracted from soybean oil, along with hydroxyl-terminated polybutadiene (HTPB). The lactic acid was esterified with ethylene glycol to produce a sustainable chain extender which was used to increase the molecular weight of the final polymer. FTIR spectroscopy and scanning electron microscopy (SEM) were used for the characterization of the PU samples. The thermal degradation behavior and wetting ability of the PUs were also determined through contact angle, indicating a gradual decrease in hydrophilicity with increasing HTPB content finally made a little hydrophobic surface in the case of PU-S4 sample (contact angle = 96.46°). The potential of these polyurethanes (PUs) as drug delivery systems was checked using gabapentin as a prototypical drug. It was dispersed into the polymer matrix via the solvent evaporation process. The analysis of drug release adhered to US Pharmacopeial guidelines was determined using 0.06 N HCl as the release medium. Sample PU-S4 showed a higher drug release, reaching 56.0 % after 6 h. Additionally, a regular trend was observed in different PU samples, suggesting an increase in HTPB content with a decrease in drug release.

Polysaccharide Hydro-Gel from Arid Plant Seed

There is a limited information on the structure and gelation process in mucilagepolysaccharides because of the complex conformation and non-homogeneity of the constituent polysaccharides that typically show large molecular weights in excess of 1 MDa. Only a few works have been done in this area of characterizing mucilage structure and rheological behaviour for different gel solutions. Exploring this area would surely open the new horizons for drug delivery, soil conditioning and pharmaceutical industry. In this study, we aimed to extract polysaccharides found in P.ovata Seed (Isabgol) via mucilage extraction controlling molecular weight of polymers in hot water extraction stage and tried to formulate gel formation dissolving different conc. of extracted freeze-dried material along with the characterization of gel network through Rheological studies and Dynamic Light Scattering (DLS) studies in different solvents. The study confirmed the relationship between molecular associations, chain relaxation time and entanglement behaviour of P. ovata hot water extracted (HW) solutions using polydispersity index and shear rheology. Moreover, two power law regions obtained for different concentration solution are of great importance because of their wide applications in the industrial prospective.

The Characteristics of Polyester Concrete with Local Sand of East Borneo as Filter

Concrete is a mixture of coarse aggregate and fine aggregate mixed with water and cement as a binder and filler. The disadvantages of traditional concrete are that high water absorption causes low chemical resistance, low modulus of elasticity, low impact strength and a long hardening time to reach its maximum properties, namely 28 days. The solution to these shortcomings that is being developed for construction material applications is by using polymers as polymer concrete. In this research, polyester resin and sand aggregate were used as basic materials. Polyester resin is a type of thermosetting polymer that is widely used in various applications such as automotive parts, composites and construction because of its suitable processing characteristics and affordable price. Meanwhile, the sand used is local Kalimantan sand, where from the XRF and XRD test results, local Kalimantan sand is included in the silica sand type. This research varies the weight fraction of polyester resin used to determine its effect on polymer concrete characteristics such as porosity, water absorption, compressive strength, and macro observations. Variations in the polymer weight fraction used were 20%, 25% and 30%. Compressive strength testing was carried out at the age of 7 days of concrete. The results of the porosity test show that the average porosity of all variations is ± 0.5%. Meanwhile, the average value of water absorption for all fractions is 0.2%. And the highest average value of compressive strength in the 30% polyester resin weight fraction was 66.9 MPa. So it can be concluded that all variations meet SNI standards to become concrete materials.

Characterization of the surface-active exopolysaccharide produced by Halomonas sp TGOS-10: Understanding its role in the formation of marine oil snow.

In this study, we characterize the exopolymer produced by Halomonas sp. strain TGOS-10 -one of the organisms found enriched in sea surface oil slicks during the Deepwater Horizon oil spill. The polymer was produced during the early stationary phase of growth in Zobell's 2216 marine medium amended with glucose. Chemical and proton NMR analysis showed it to be a relatively monodisperse, high-molecular-mass (6,440,000 g/mol) glycoprotein composed largely of protein (46.6% of total dry weight of polymer). The monosaccharide composition of the polymer is typical to that of other marine bacterial exopolymers which are generally rich in hexoses, with the notable exception that it contained mannose (commonly found in yeast) as a major monosaccharide. The polymer was found to act as an oil dispersant based on its ability to effectively emulsify pure and complex oils into stable oil emulsions-a function we suspect to be conferred by the high protein content and high ratio of total hydrophobic nonpolar to polar amino acids (52.7:11.2) of the polymer. The polymer's chemical composition, which is akin to that of other marine exopolymers also having a high protein-to-carbohydrate (P/C) content, and which have been shown to effect the rapid and non-ionic aggregation of marine gels, appears indicative of effecting marine oil snow (MOS) formation. We previously reported the strain capable of utilising aromatic hydrocarbons when supplied as single carbon sources. However, here we did not detect biodegradation of these chemicals within a complex (surrogate Macondo) oil, suggesting that the observed enrichment of this organism during the Deepwater Horizon spill may be explained by factors related to substrate availability and competition within the complex and dynamic microbial communities that were continuously evolving during that spill.

Indigo-dyed cellulose fibers and synthetic polymers in surface-feeding seabird chick regurgitates from the Gulf of Alaska

We provide evidence of anthropogenic materials ingestion in seabirds from a remote oceanic area, using regurgitates obtained from black-legged kittiwake (Rissa tridactyla) chicks from Middleton Island (Gulf of Alaska, USA). By means of GPS tracking of breeding adults, we identified foraging grounds where anthropogenic materials were most likely ingested. They were mainly located within the continental shelf of the Gulf of Alaska and near the Alaskan coastline. Anthropogenic cellulose fibers showed a high prevalence (85 % occurrence), whereas synthetic polymers (in the micro- and mesoplastics dimensional range) were less frequent (20 %). Most fibers (60 %) were blue and we confirmed the presence of indigo-dyed cellulosic fibers, characteristic of denim fabrics. In terms of mass, contamination levels were 0.077 μg g−1 wet weight and 0.009 μg g−1 wet weight for anthropogenic microfibers and synthetic polymers, respectively. These results represent the only recent report of contamination by anthropogenic fibers in seabirds from the Gulf of Alaska.