Polysaccharide Nanostructures

Polysaccharides are carbohydrate polymers where sugar units are linked together through glycosidic linkages. In living organisms polysaccharides are the structural polymers that provide support (e.g., cellulose in plants or chitin in arthropods) or the sources of energy for plant development (e.g., starch). Polysaccharides are routinely used in the food industry, most frequently as thickeners, stabilizers of dispersions (emulsions, foams) or structuring agents of water and air

Open windrow composting of polymers: An investigation into the rate of degradation of polyethylene

The compostability of degradable polymers under open windrow composting conditions is explored within this paper. Areas for consideration were the use of, and impacts of, degradable polyethylene (PE) sacks on the composting process and the quality of the finished compost product. These factors were investigated through polymer weight loss over the composting process, the amount of polymer residue and chemical contaminants in the finished compost product, the windrow temperature profiles and a bioassay to establish plant growth and germination levels using the final compost product. This trial also included a comparative study of the weight loss under composting conditions of two different types of ‘degradable’ polymer sacks currently on the European market: PE and a starch based product. Statistical analysis of the windrow temperature profiles has led to the development of a model, which can help to predict the expected trends in the temperature profiles of open compost windrows where the organic waste is kerbside collected using a degradable PE sack

Wheat glutenin subunits and dough elasticity: findings of the EUROWHEAT project

Detailed studies of wheat glutenin subunits have provided novel details of their molecular structures and interactions which allow the development of a model to explain their role in determining the visco-elastic properties of gluten and dough. The construction and analysis of near-isogenic and transgenic lines expressing novel subunit combinations or increased amounts of specific subunits allows differences in gluten properties to be related to the structures and properties of individual subunits, with potential benefits for the production of cultivars with improved properties for food processing or novel end user

Analysis of gene mutation in plant cell wall by dielectric relaxation

Arabidopsis Thaliana is a plant composed mainly of cellulose and lignin. Geneticists need techniques able to make differences at the molecular level between modified plants (DML6, CAD C/D) and non-modified ones. Thermo-stimulated current (TSC) analysis is a promising route to identify gene mutations. For the non-modified plant, at low temperatures, TSC thermograms highlight three dielectric relaxation modes. From −150 to −110 ◦C, γCellulose is attributed to CH2OH and –OH groups of cellulose. Between −110 and −80 ◦C, βLignin is detected. From −80 to −40 ◦C, βCellulose is characteristic of the molecular mobility of glycosidic linkages. For the CAD C/D modified plants, only γCellulose and βLignin are observed; due to analogous enthalpy values, those modes have the same molecular origin as in the non-modified plant. So, the βLignin mode is associated with the molecular mobility of the lignin-OH groups. The CAD C/D gene mutation changes the chemical structure of lignin, which promotes hydrogen bonds in the network and inhibits molecular mobility of glucosidic rings. It is also interesting to note that the DML6 gene mutation induces a higher cooperativity of this βCellulose relaxation than in wild vegetal composites. In fact, this mutation promotes molecular mobility of glycosidic rings thanks to β1–4 glycosidic linkages

Novel hydrogels based on polysaccharides for soft tissue regeneration: preparation and characterization

Předložená diplomová práce se zabývá přípravou, síťováním a fyzikálně-chemickou charakterizací hydrogelů na bázi polysacharidů. Cílem práce bylo vyvinout elastické filmy, které by mohly být použity pro vlhké hojení ran. Teoretická část shrnuje současné způsoby regenerace měkkých tkání a jejích náhradách (ať už se jedná o přírodní nebo syntetické materiály). Zároveň jsou zdůrazněny základní informace o přírodních polysacharidech (chemická struktura, rozpustnost, tepelná a pH stabilita atd.), jejich modifikace a chemické síťování. Experimentální část je zaměřena na modifikaci přírodní gumy Karaya tak, aby transparentní hydrogely měly nastavitelnou hydrolytickou stabilitu. Vzorky byly analyzovány pomocí FTIR, TGA následované vyhodnocením bobtnání a hydrolytické degradace. Z výsledků vyplynulo, že chemická modifikace zvýšila stabilizaci elastického filmu z přírodního polysacharidu ve vodě až na 25 dní. Díky řízené degradaci a vysoké absorpci vody (85 - 96%) jsou tyto nové hydrogely využitelné především pro vlhké hojení ran (např. popálenin).Presented diploma thesis deals with preparation, crosslinking and physico-chemical characterization of natural polysaccharide-based hydrogels. The aim of the work was to evolve elastic thin films with potential application for moist wound healing. The theoretical part summarizes the state-of-art about regeneration of soft tissues and their substitutes (synthetic or nature). There are pointed out the basic information about natural polysaccharide gums (chemical structure, solubility, heat and pH stability etc.), its modification and chemical crosslinking. The experimental part is focused on the modification of natural gum Karaya in order to make transparent hydrogels with adjustable hydrolytical stability. Samples were analyzed by FTIR, TGA followed by evaluation of swelling properties and hydrolytical degradation. Based on the results, chemical modification helped to stabilize polysaccharide hydrogels in water up to 25 days which is useful mainly for moist wound healing (e.g. after burns) because of high values of water uptake (from 85 up to 96%).

OLIgo mass profiling (OLIMP) of extracellular polysaccharides.

The direct contact of cells to the environment is mediated in many organisms by an extracellular matrix. One common aspect of extracellular matrices is that they contain complex sugar moieties in form of glycoproteins, proteoglycans, and/or polysaccharides. Examples include the extracellular matrix of humans and animal cells consisting mainly of fibrillar proteins and proteoglycans or the polysaccharide based cell walls of plants and fungi, and the proteoglycan/glycolipid based cell walls of bacteria. All these glycostructures play vital roles in cell-to-cell and cell-to-environment communication and signalling. An extraordinary complex example of an extracellular matrix is present in the walls of higher plant cells. Their wall is made almost entirely of sugars, up to 75% dry weight, and consists of the most abundant biopolymers present on this planet. Therefore, research is conducted how to utilize these materials best as a carbon-neutral renewable resource to replace petrochemicals derived from fossil fuel. The main challenge for fuel conversion remains the recalcitrance of walls to enzymatic or chemical degradation due to the unique glycostructures present in this unique biocomposite. Here, we present a method for the rapid and sensitive analysis of plant cell wall glycostructures. This method OLIgo Mass Profiling (OLIMP) is based the enzymatic release of oligosaccharides from wall materials facilitating specific glycosylhydrolases and subsequent analysis of the solubilized oligosaccharide mixtures using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS)(1) (Figure 1). OLIMP requires walls of only 5000 cells for a complete analysis, can be performed on the tissue itself(2), and is amenable to high-throughput analyses(3). While the absolute amount of the solubilized oligosaccharides cannot be determined by OLIMP the relative abundance of the various oligosaccharide ions can be delineated from the mass spectra giving insights about the substitution-pattern of the native polysaccharide present in the wall. OLIMP can be used to analyze a wide variety of wall polymers, limited only by the availability of specific enzymes(4). For example, for the analysis of polymers present in the plant cell wall enzymes are available to analyse the hemicelluloses xyloglucan using a xyloglucanase(5, 11, 12, 13), xylan using an endo-beta-(1-4)-xylanase (6,7), or for pectic polysaccharides using a combination of a polygalacturonase and a methylesterase (8). Furthermore, using the same principles of OLIMP glycosylhydrolase and even glycosyltransferase activities can be monitored and determined (9)

Nanocellulose as building block for novel materials

This thesis describes the fabrication of novel green materials using nanocellulose as the building block. Bacterial cellulose (BC) was used as the nanocellulose predominantly in this work. BC is highly crystalline pure cellulose with an inherent fibre diameter in the nano-scale. A single BC nanofibre was found to possess a Young’s modulus of 114 GPa. All these properties are highly favourable for using BC as a nanofiller/reinforcement in green nanocomposite materials. In this work, the surface of BC was rendered hydrophobic by grafting organic acids with various aliphatic chain lengths. These surface-modified BC was used as nanofiller for poly(L-lactide) (PLLA). Direct wetting measurements showed that the BC nanofibre-PLLA interface was improved due to the hydrophobisation of BC with organic acids. This led to the production of BC reinforced PLLA nanocomposites with improved tensile properties. Nanocellulose can also be obtained by grinding of wood pulp, producing nanofibrillated cellulose (NFC). The surface and bulk properties of one type of NFC and BC were compared in this work. Furthermore, the reinforcing ability of NFC and BC was also studied and it was observed that there is no significant difference in the mechanical performance of NFC or BC reinforced nanocomposites. A novel method based on slurry dipping to coat sisal fibres with BC was developed to modify the surface of natural fibres. This method can produce either (i) a densely BC coating layer or (ii) “hairy” BC coated sisal fibres. Randomly oriented short BC coated sisal fibre reinforced hierarchical composites were manufactured. It was found that hierarchical (nano)composites containing BC coated sisal fibres and BC dispersed in the matrix were required to produce composites with improved mechanical properties. This slurry dipping method was also extended to produce robust short sisal fibre preforms. By infusing this preform with a bio-based thermosetting resin followed by curing, green composites with significantly improved mechanical properties were produced. BC was also used as stabiliser and nano-filler for the production of macroporous polymers made by frothing of acrylated epoxidised soybean oil followed by microwave curing

Bioplastics made from upcycled food waste. Prospects for their use in the field of design

In recent years, the negative effects on the environment of the intensive use of synthetic, oil-derived plastics to make products, even those with a limited required duration, have given renewed impetus to the search for biodegradable and/or compostable materials obtained from renewable sources, particularly biopolymers derived from vegetable, animal or microbial matter that could prove a valid alternative in a number of applications: not only in the packaging industry, but also for making objects with a longer required duration. Indeed, as well as offering the possibility of being used as they are, immediately after having undergone traditional-type mechanical processing, it is also possible to mix, supplement and modify them both on a macro- and nanometric scale, allowing us to significantly increase their properties and performance and adapt them to a wide variety of needs. However, the real challenge is to create new materials from food waste and not from specially grown crops, whose production has, in any case, an environmental cost. This allows us to reduce the waste produced when processing foods, which is usually a practical problem and involves a considerable investment in economic terms. It also helps us address one of the worst problems of our time: that of the waste that sees a third of the food produced worldwide lost along the various steps of the food production chain. There is an enormous variety of vegetable, animal and microbial waste that can be used to create biopolymers: from the orange peels left over from fruit juice production to the grapes used to produce wine; from chocolate production waste to egg shells and prawns. We can extract the starches, cellulose, pectin, chitin, lactic acid, collagen, blood proteins and gelatin that form the basis of bioplastics from these materials, either extracting them directly or using mechanical or chemical processes. These are true ‘treasure troves’ of substances that can become useful materials thanks to processes of varying complexity. In recent years, the testing of substances made from food waste has increased significantly; the sheer abundance of raw materials that can be used to make them has encouraged institutional research, as well as an approach to project development that has been widely embraced by many young designers who craft these materials. Nevertheless, there is still no systematic record of the results achieved. This has slowed down their adoption, which in contrast offers enormous potential that is still almost entirely unexplored. This paper considers all aspects of these materials, starting with the most interesting experiments underway, and envisages possible future scenarios