Polysaccharide Esters Research Articles

Low-dielectric thermosetting resins derived from polysaccharide unsaturated esters

Printed circuit boards (PCBs) contain metals and plastics, with the latter often incinerated after disposal, leading to carbon dioxide emissions. This study focuses on developing biomass-based thermosetting resins derived from polysaccharides. Cellulose and α-1,3-glucan were introduced with unsaturated (2-butenoate) and saturated (hexanoate) ester groups to achieve appropriate properties for PCB applications. The synthesized polysaccharide esters, cellulose-2-butenoate-hexanoate and α-1,3-glucan-2-butenoate-hexanoate, demonstrated thermoformability at 150 °C, suitable for being laminated on circuit lines. After heating at 220 °C for 1 hour, the unsaturated parts of the polymers crosslinked, increasing the glass transition temperature to over 230 °C, making them potentially durable for the soldering process. The dielectric constant and dissipation factor of the crosslinked resins ranged from 2.5 to 2.7 and 0.012 to 0.014, respectively, outperforming conventional epoxy resins to reduce transmission loss. Additionally, the crosslinked films exhibited robust mechanical properties with tensile strengths exceeding 50 MPa. These results indicate that polysaccharide unsaturated esters are promising for use as PCB insulating resins, providing a sustainable alternative to petroleum-based materials.

Synthesis, characterization and seawater biodegradability of paramylon mix ester derivatives with different DS

A two-step synthesis method was established to prepare paramylon mix ester derivatives with low total DS by introducing long chain hexanoate into biodegradable polysaccharide esters with short chain acetate. The relationship between the chemical structure of paramylon mix esters and their thermal properties and seawater biodegradability was investigated. Among the possible hydroxyl groups of paramylon backbone, hydroxyl group on C6 position is prior to be substituted for both paramylon acetate (PaAc) and paramylon acetate hexanoate (PaAcHex). Prepared paramylon esters are amorphous and more thermal stable than neat paramylon. PaAcHex showed lower Tg and more flexibility when hexanoate were added more. The capability of biodegradability of mix esters with different collocations was also determined. Hexanoate with low DS provides paramylon esters with effective mechanical properties without losing the seawater biodegradability. These results of collocations of short and long ester chains were verified to be an effective thought to realize the coexistence of thermoformability, mechanical property and biodegradability.

Microbial decomposition of biodegradable plastics on the deep-sea floor

Microbes can decompose biodegradable plastics on land, rivers and seashore. However, it is unclear whether deep-sea microbes can degrade biodegradable plastics in the extreme environmental conditions of the seafloor. Here, we report microbial decomposition of representative biodegradable plastics (polyhydroxyalkanoates, biodegradable polyesters, and polysaccharide esters) at diverse deep-sea floor locations ranging in depth from 757 to 5552 m. The degradation of samples was evaluated in terms of weight loss, reduction in material thickness, and surface morphological changes. Poly(l-lactic acid) did not degrade at either shore or deep-sea sites, while other biodegradable polyesters, polyhydroxyalkanoates, and polysaccharide esters were degraded. The rate of degradation slowed with water depth. We analysed the plastic-associated microbial communities by 16S rRNA gene amplicon sequencing and metagenomics. Several dominant microorganisms carried genes potentially encoding plastic-degrading enzymes such as polyhydroxyalkanoate depolymerases and cutinases/polyesterases. Analysis of available metagenomic datasets indicated that these microorganisms are present in other deep-sea locations. Our results confirm that biodegradable plastics can be degraded by the action of microorganisms on the deep-sea floor, although with much less efficiency than in coastal settings.

Esters of Inulin and Tall Oil Fatty Acids

The possibility of obtaining polysaccharide esters based on large-scale products of plant origin: inulin and tall oil fatty acids, was studied. Carbohydrate esters of the biopolymer inulin and higher unsaturated acids were synthesized by acylation with acid chlorides under various conditions: in a water–chloroform mixture in the presence of sodium hydroxide and sodium salts of tall oil fatty acids, as well as in a pyridine–1,4-dioxane mixture. The yield of polysaccharide esters was 67–82%, the maximum yield was detected during the acylation of inulin in the pyridine–1,4-dioxane system

Clickable polymers accessible through nucleophilic substitution on polysaccharides: A sophisticated route to functional polymers

This review article is dedicated to special polysaccharide esters – the polysaccharide toluenesulfonic acid esters (tosylates) and polysaccharide carbonate esters. After describing the specifics of the synthesis, particular emphasis is placed on the use of polysaccharide tosylates and polysaccharide phenyl carbonates for subsequent modification by nucleophilic substitution (SN) reactions. For this purpose, the advantages and limitations of the respective derivatives are discussed with regard to their application in chemical modification with nucleophiles containing functional groups. A few functional polysaccharide derivatives and their properties are presented. Finally, reactive derivatives for click chemistry approaches are featured. These can be prepared starting from the reactive intermediate of either polysaccharide tosylate or polysaccharide phenyl carbonate.

Renewable thermoplastics – Starch fatty acid esters as alternatives to synthetics

Thermoplastics are an important class of polymers that find widespread use in a broad variety of applications. Because of environmental concerns regarding the lack of biodegradability of synthetic thermoplastics, green alternatives are increasingly studied that should be both based on renewable resources and biodegradable. In this regard, polysaccharide esters of naturally occurring fatty acids are in the center of interest.

Manufacture of strong melt-spun fibers derived from α-1,3-glucan esters and determination of their crystal structures and crystalline elastic moduli

Melt-spun fibers derived from α-1,3-glucan esters were successfully manufactured without a plasticizer. Fibers derived from α-1,3-glucan butyrate had a tensile strength of over 1000 MPa. The crystalline structures of the α-1,3-glucan esters were determined as monoclinic systems by X-ray diffraction. The linear esters comprised threefold helices and the branched esters comprised five- or eightfold helices. The crystalline elastic moduli (El) parallel to the fiber axes were determined by time-resolved X-ray diffraction with tensile tests. Specifically, α-1,3-glucan propionate, α-1,3-glucan butyrate, and α-1,3-glucan valerate—which had threefold helices—had El values of 24.0, 12.4, and 4.2 GPa, respectively. In contrast, α-1,3-glucan 2-methyl valerate—which had a fivefold helix—had an El of 1.0 GPa. Therefore, the El decreased as the length of the side chain and the helix inclination increased. We concluded that El values of polysaccharide esters are not dependent on the glycosidic linkages, but rather on helix structures.

Cutin:xyloglucan transacylase (CXT) activity covalently links cutin to a plant cell-wall polysaccharide

The shoot epidermal cell wall in land-plants is associated with a polyester, cutin, which controls water loss and possibly organ expansion. Covalent bonds between cutin and its neighbouring cell-wall polysaccharides have long been proposed. However, the lack of biochemical evidence makes cutin–polysaccharide linkages largely conjectural. Here we optimised a portfolio of radiochemical assays to look for cutin–polysaccharide ester bonds in the epidermis of pea epicotyls, ice-plant leaves and tomato fruits, based on the hypothesis that a transacylase remodels cutin in a similar fashion to cutin synthase and cutin:cutin transacylase activities. Through in-situ enzyme assays and chemical degradations coupled with chromatographic analysis of the 3H-labelled products, we observed that among several wall-related oligosaccharides tested, only a xyloglucan oligosaccharide ([3H]XXXGol) could acquire ester-bonds from endogenous cutin, suggesting a cutin:xyloglucan transacylase (CXT). CXT activity was heat-labile, time-dependent, and maximal at near-neutral pH values. In-situ CXT activity peaked in nearly fully expanded tomato fruits and ice-plant leaves. CXT activity positively correlated with organ growth rate, suggesting that it contributes to epidermal integrity during rapid expansion. This study uncovers hitherto unappreciated re-structuring processes in the plant epidermis and provides a step towards the identification of CXT and its engineering for biotechnological applications.

Synthesis and characterization of α-1,3-alt-α-1,4-glucan (nigeran) ester derivatives

Nigeran is a linear α-d-glucan with alternating α-1,3- and α-1,4-glycosidic linkages. Nigeran (α-1,3-alt-α-1,4-glucan) esters with different ester chain lengths were synthesized from high molecular weight nigeran extracted from mycelium of Aspergillus oryzae over-expressing a nigeran synthase gene derived from Aspergillus luchuensis. All prepared nigeran esters were crystalline polymers with high melting point, including those with ester groups longer than octanoate. This unique crystallization behavior is not reported in other polysaccharide esters. Both solvent-cast and melt-quenched films were self-standing and high transparency. Solvent-cast films were stretched up to four times the initial length and showed well-oriented X-ray fiber diagrams. Nigeran propionate had twofold screw symmetry along the molecular axis (same as neat nigeran), suggesting that the molecular conformation remained unchanged despite esterification. This result indicates that the molecular conformation of nigeran with its α-1,3-alt-α-1,4-glycosidic linkage is very stable despite chemical modification and retains high crystallinity.

Patterned dextran ester films as a tailorable cell culture platform

The elucidation of cell-surface interactions and the development of model platforms to help uncover their underlying mechanisms remains vital to the design of effective biomaterials. To this end, dextran palmitates with varying degrees of substitution were synthesised with a multipurpose functionality: an ability to modulate surface energy through surface chemistry, and an ideal thermal behaviour for patterning. Herein, dextran palmitate films are produced by spin coating, and patterned by thermal nanoimprint lithography with nano-to-microscale topographies. These films of moderately hydrophobic polysaccharide esters with low nanoscale roughness performed as well as fibronectin coatings in the culture of bovine aortic endothelial cells. Upon patterning, they display distinct regions of roughness, restricting cell adhesion to the smoothest surfaces, while guiding multicellular arrangements in the patterned topographies. The development of biomaterial interfaces through topochemical fabrication such as this could prove useful in understanding protein and cell-surface interactions.

Recent developments in microbial polyester fiber and polysaccharide ester derivative research

To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation. To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.

Synthesis of α-1,3-Glucan branched ester derivatives with excellent thermal stability and thermoplasticity

α-1,3-Glucan is a linear homopolymer enzymatically polymerized from sucrose using recombinant glucosyl transferase J (GtfJ) enzyme. α-1,3-Glucan branched ester derivatives were synthesized from branched carboxylic acids and trifluoroacetic anhydride in a heterogeneous reaction. These derivatives showed unconventional thermal properties compared with other polysaccharide ester derivatives and oil-based plastics. The melting temperature (Tm) of the α-1,3-Glucan branched ester derivatives increased in proportion to the side chain length, which has not been observed for other polysaccharide ester derivatives. In addition, isobutyrate ester derivatives (iso-branched ester derivatives) and pivalate ester derivatives (tert-branched ester derivatives) showed extremely high glass transition temperatures (Tg) of 206 and 202 °C, respectively, which were much higher than those of commercial plastics, such as polyethylene terephthalate (PET: 69 °C) and polycarbonate (140 °C), and super engineering plastics, such as polyether ether ketone (PEEK: 142 °C). Furthermore, these two types of branched ester derivatives showed excellent thermoplasticity at temperatures below the thermal decomposition temperature. Therefore, α-1,3-Glucan branched ester derivatives demonstrate the possibility of realizing both high thermal stability and thermoplasticity.

Novel amphiphilic dextran esters with antimicrobial activity

New amphiphilic dextran esters were obtained by polysaccharide functionalization with different substituted 1,2,3-triazoles-4-carboxylic acid via in situ activation with N, N′-carbonyldiimidazole. Nitrogen-containing heterocyclic derivatives were achieved by copper(I)-catalyzed cycloaddition reaction between organic azides and ethyl propiolate. Structural characteristics of the compounds were studied by elemental analysis, Fourier transform infrared and nuclear magnetic resonance spectroscopy (1H and 13C‐NMR). Thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction were used for esters characterization. Properties of polymeric self-associates, formed in aqueous solution, were studied by dynamic light scattering and transmission electron microscopy. The critical aggregation concentration values for dextran esters, determined by fluorescence spectroscopy, were in the range of 4.1-9.5 mg/dL. Antimicrobial activity, investigated for some of the polymers by disc-diffusion method, pointed out that polysaccharide esters were active.

Melt spinnabilities of thermoplastic paramylon mixed esters

The low thermoplasticities of polysaccharide esters make them unsuitable for melt spinning. In this study, we aimed to overcome this problem by mixed esterification of paramylon, a euglenoid β-1,3-glucan with short- and medium-chain acyl groups, as melt-spinnable materials. Thermal analyses revealed that all the synthesized paramylon mixed esters exhibited glass transition temperatures greater than 100 °C; some of them showed large differences between the melting and 5%-weight-loss temperatures (Td5s) and are extrudable through a spinneret at a temperature ~100 °C below Td5, rendering them potential candidates for the production of melt-spun filaments. Among the various compounds investigated, paramylon acetate propionates, in which the degrees of acetyl- and propionyl-group substitution were 0.5–0.7 and 2.2–2.5, respectively, could be melt-spun to yield mechanically tough crystalline monofilaments. In contrast, the melt spinning of cellulose acetate propionate, analogous to the paramylon acetate propionates in terms of acyl substituents, their substitution degrees, and molecular weights, but differs from it in terms of the glucose linkage mode (i.e., β-1,3 vs β-1,4), yielded brittle, charred, and short filaments. Curdlan acetate propionate, another analogue with a degree of polymerization five times larger than that of paramylon mixed esters, was not extrudable due to the lack of thermoplasticity. Therefore, we herein confirmed the superiority of paramylon as a primary raw material for melt-spun filaments.

Preparation of pure gum raw materials-low brown algae application

Octenylsuccinate starch ester, also called pure gum, is non-toxic and odourless modified starch which is widely used in many food fields. This study synthesized pure gum in a reaction kettle using the low molecular weight trehalose and octenyl succinic acid. An orthogonal test was carried out to find how the reaction factors affect the synthetization of octenylsuccinic acid polysaccharide ester and to optimize the reaction at single factor level. The optimal products were obtained using 1:2 of octenylsuccinic acid: alginic acid, catalysed by 0.1% p-toluenesulfonic acid catalyst for 1.5 h at 200°C under vacuum conditions. The gained product contains up to 46% of seaweed gel monoesters. The degree of esterification of the polysaccharide is controlled by the use of the small-molecule trehalose. Compared with the traditional methods, our process can reduce raw material cost and improve emulsification stability of pure gum. These all can significantly improve the market competitiveness of pure gum products.

Methane formation and oxidation by prokaryotes

The review deals with systematization and generalization of new information concerning the phylogenetic and functional diversity of prokaryotes involved in the methane cycle. Methane is mostly produced by methanogenic archaea, which are responsible for the terminal stage of organic matter decomposition in a number of anoxic ecotopes. Although phylogeny, physiology, and biochemistry of methanogens have been extensively studied, important discoveries were made recently. Thus, members of deep phylogenetic lineages within the Euryarchaeota phylum (Methanomassiliicoccales, “Candidatus Methanofastidiosa,” “Methanonatronarchaeia”) and even outside it (“Ca. Verstraetearchaeota” and “Ca. Bathyarchaeota”) were reported to carry out methyl-reducing methanogenesis. Moreover, evidence was obtained on aerobic methane production by marine heterotrophic bacteria, which demethylate polysaccharide esters of methylphosphonic acid. Methanotrophic microorganisms oxidize methane both aerobically and anaerobically, decreasing significantly the release of this greenhouse gas into the atmosphere. In the presence of oxygen methane is oxidized by methanotrophic members of Alpha- and Gammaproteobacteria, as well as by Verrucomicrobia. Methanotrophic gammaproteobacteria have been recently revealed in hypoxic and even anoxic environments, where they probably oxidize methane either in a trophic consortium with oxygenic phototrophs and/or methylotrophs or using electron acceptors other than oxygen. Anaerobic methane oxidation has been known for a long time. Sulfat- and nitrate-dependent anaerobic methane oxidation carried out by the ANME archaea via reverse methanogenesis are the best studied processes. While metal-dependent anaerobic methane oxidation is considered possible, the mechanisms and agents responsible for this process have not been reliably identified. Intracellular oxygen production during nitrite-dependent anaerobic methane oxidation was shown for bacteria “Ca. Methylomirabilis oxyfera.” These findings stimulate interest in the processes and microorganisms of the methane cycle.

Amino acids modified konjac glucomannan as green corrosion inhibitors for mild steel in HCl solution

Konjac glucomannan (KGM) was modified with amino acids to synthesize polysaccharide esters (KGMA and KGMH) which were evaluated as corrosion inhibitor for mild steel in 0.5M HCl solution by weight loss tests, Tafel curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The synthetic polymers were found to have the lower water absorbency and the higher water solubility than KGM. Gravimetric measurements showed the maximum efficiencies of KGMA and KGMH for decreasing the corrosion rate of metal at 2000ppm are up to 89.9% and 92.4%, respectively. Polarization curves indicated polysaccharide esters could retard both hydrogen evolution reaction and metal dissolution reaction and that the inhibitory effect was concentration dependent. Besides, EIS studies demonstrated the corrosion resistance of mild steel in hydrochloric acid was enhanced by polymer additives. The observations on mild steel surface by SEM suggested the metallic substrate obtained good protection against corrosion in inhibitor-containing HCl solution. The adsorptive behavior of polymer molecules including physisorption and chemisorption obeyed Langmuir isotherm and UV–vis spectra revealed the formation of inhibitor-ion complex. The better performance of KGMH on corrosion inhibition was attributed to the easier transfer of π-electron or n-electron, which was confirmed by quantum chemical calculations.

Recyclable and scalable organocatalytic transesterification of polysaccharides in a mixed solvent of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide

In this manuscript, the scalability and recyclability of the catalytic transesterifications of polysaccharides with 1-ethyl-3-methylimidazolium acetate (EmimOAc) as both the solvent and the organocatalyst were evaluated. For the organocatalytic transesterifications of cellulose with EmimOAc, EmimOAc was recycled four times without an obvious decrease in its catalytic activity, and the recovery ratio of EmimOAc was sufficiently high (at least 96 wt%). To show the applicability of EmimOAc-catalyzed transesterifications, the EmimOAc-catalyzed cellulose modification was expanded to a gram-scale reaction with various polysaccharide sources, such as pulps, rayon, xylan, pullulan, and dextrin, which provides the corresponding polysaccharide esters with a practically perfect degree of substitution values. The scalability and recyclability in transesterifications of polysaccharides with 1-ethyl-3-methylimidazolium acetate (EmimOAc) as both the solvent and organocatalyst was confirmed. In addition, the EmimOAc-catalyzed transesterification protocol was expanded to a gram-scale reaction with various polysaccharide sources, such as pulps, rayon, xylan, pululan, and dextrin.

Hydroboration–oxidation: A chemoselective route to cellulose ω-hydroxyalkanoate esters

We describe the first synthesis of hydroxy-functionalized polysaccharide esters via chemoselective olefin hydroboration–oxidation in the presence of ester groups. Cellulose esters with terminally olefinic side chains were first synthesized by esterification of commercially available cellulose esters (e.g., cellulose acetate) with undec-10-enoyl chloride or pent-4-enoyl chloride. Subsequent two-step, one-pot hydroboration–oxidation reactions of the cellulose esters were performed, using 9-borabicyclo[3.3.1]nonane as hydroboration agent, followed by oxidizing the intermediate borane to a hydroxyl group using mildly alkaline H2O2. Sodium acetate was used as a weak base to catalyze the oxidation, thereby minimizing undesired ester hydrolysis. Characterization methods including FTIR, 1H, and 13C NMR proved the selectivity of the hydroboration–oxidation pathway, providing a family of novel cellulose ω-hydroxyalkanoyl esters that were previously difficult to access.

Matrix Binding of Ochratoxin A during Roasting

The mycotoxin ochratoxin A is degraded during coffee roasting by up to 90%. During this process, the two known degradation products, 14R-ochratoxin A and 14-decarboxy-ochratoxin A are formed. However, there is still an unexplained loss of more than 50% ochratoxin A. Here, we describe the binding of ochratoxin A to coffee polysaccharides via esterification as a further thermal reaction. This ester formation was studied by heating ochratoxin A with methyl α-d-glucopyranoside, a model compound to mimic polysaccharides. From this experiment, (22 → 6') ochratoxin A-methyl-α-d-glucopyranoside ester was isolated and characterized as a reaction product, showing the general ability of ochratoxin A for esterification with carbohydrates at roasting temperatures. Subsequently, a sample preparation protocol for the detection of ochratoxin A saccharide esters based on an enzymatic cleavage and purification using immunoaffinity chromatography was developed and applied. The detection was carried out by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Using this method, it was possible to detect ochratoxin A polysaccharide esters formed during roasting of artificially contaminated coffee, confirming the results of the previous model experiments. Thus, the formation of ochratoxin A esters is a further explanation for the loss of ochratoxin A during coffee roasting.