A NATURAL FIT FOR SUSTAINABLE DEVELOPMENT
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Polysaccharides are biologically produced (bio-based) materials that have a unique combination of functional properties and environmentally friendly features. Polysaccharides are also polymers and their long chain structures, as in man-made polymers, provide good mechanical properties for applications such as fibers, films, adhesives, melt processable plastics, thickeners, rheology modifiers, hydrogels, drug delivery agents, emulsifiers, etc. They are renewable materials, produced from other biological compounds, and generally are non-toxic and biodegradable. These features make polysaccharide materials a natural fit for sustainable development. Commercially available products include starch, cellulose and its derivatives (such as cellulose acetate, carboxymethyl cellulose, and methyl cellulose), sodium alginate, xanthan gum, dextran, carrageenan, and hyaluronic acid. Research continues to bring us new materials with improved performance and lower costs. This website is dedicated to promoting the commercial development of polysaccharide materials. Explore this website and learn more about the chemical and physical properties of polysaccharides, their applications and markets, and commercial sources. Featured below are highlights of recent articles about exciting developments with polysaccharide materials. “From ophthalmic drug delivery to inexpensive thermoplastics, biomaterials made
from polysaccharide[s] offer sometimes surprising solutions to modern problems.
Visitors will learn a lot from this site.” |
 Polysaccharide sources: wood (cellulose), seaweed (alginate), bacteria (xanthan gum) |
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| NEWS HARVEST |
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June 2009 - The goal: competitively priced microbial polysaccharides
A number of polysaccharides are commercially produced by fermentation of renewable resources – for example, xanthan gum, gellan, dextran, and pullulan. 
They generally find use in higher value applications such as thickeners and rheology modifiers in food and medical applications. Pullulan is a water-soluble, colorless material that makes strong films with high adhesion and oxygen barrier properties. In addition, it is edible and sold in food applications, such as protective coatings and packaging. A large market is also in capsules for pharmaceuticals. Chemically, pullulan is a polymer of glucose repeat units with α-(1,4) linkages, much like starch, but with a portion of 1,6-linkages. This is enough to disrupt the regular structure and render the polymer with properties that produce amorphous, flexible films and greater water solubility. Thus it has very attractive physical and mechanical properties. However the cost to produce it is still significantly greater than similar polymeric materials produced from petrochemical sources. However, with a driving force to production of more sustainable and environmentally friendly materials, efforts continue to improve the production cost of pullulan. These improvements should be applicable to other microbial polysaccharides and help their overall commercial development and broader utility.
In a recent publication, researchers described improvements to the pullulan production process. Key challenges in the production process lie in the product isolation after the fermentation is complete - in particular, separation of proteins, color bodies, and other impurities. Currently proteins are separated by selective precipitation of the polysaccharide from an aqueous solution by dilution with ethanol. Much but not all of the protein contaminant remains in solution. Color is conventionally removed by carbon absorption although separation of the resulting carbon from the viscous solution is difficult and leads to product losses. New improvements which optimized the recovery of pullulan have been demonstrated and involve separating cell mass by centrifugation, heating the broth at 80 C to denature and precipitate protein, decolorization by treatment with hydrogen peroxide, concentration by vacuum distillation of water, and then ethanol precipitation. The final pullulan product was obtained with a high recovery and in higher purities than commercial material (“Downstream processing of pullulan from fermentation broth,” S Wu, Z Jin, JM Kim, Q Tong, and H Chen, Carbohydrate Polymers 2009, 77, 750-753 [abstract).
February 2009 - Biodegradable, polysaccharide based scale inhibitor for industrial water treatment
The average person is largely unaware of the industrial water treatment business. Yet it is very 
important for the efficient workings of industry today. Water is used in many industrial operations, for example in cooling towers or geothermal systems for heat transfer, or in oilfield operations to maximize recovery of oil. The tanks, pipes, heat exchangers, etc. all must be kept clean of fouling by inorganic and organic materials which is a continual challenge. One class of chemicals employed for this purpose are scale inhibitors. They work by inhibiting crystal formation and deposition on equipment surfaces. Commercial products are phosphonates and low molecular weight polyacrylates and polymaleates. Although effective, they are lacking in biodegradability which is desirable considering that the environmental fate of these materials often is discharge into water bodies.
This is where polysaccharides come in ... water soluble, polymeric, biodegradable, economical, and as a bonus, produced from renewable resources. By suitable modification of the polysaccharide structure, the required scale inhibition properties can be achieved. As described in a recent patent application (“Polysaccharide based scale inhibitor,” S Kesavan, G Woodward, F Decampo (Rhodia Inc), US Patent Application 20080277620, 2008 [full text] the galactomannan polysaccharides, such as guar gum, were converted into very effective inhibitors of calcium carbonate and barium sulfate scale formation. A combination of carboxyalkylation and partial depolymerization was employed to generate a structure that effectively inhibited formation of mineral scales and also was stable to oxidizing biocides and heat that are encountered in industrial applications. Optimum (100%) calcium carbonate scale inhibition was observed for carboxymethyl guar with a degree of substitution of 1.6, weight average molecular weight of 20,000 g/mol, and 25 ppm concentration
October 2008 - Using the polysaccharide triple helix to produce functional one-dimensional nanocomposites
We all are aware of the elegant and powerful double-stranded helix structure of DNA which is the basis of the life reproduction process. Another helix structure with amazing properties is found in some polysaccharide materials and it is being exploited to generate new composite materials for nanotechnology. β-1,3-Glucans, as found in biologically produced and commercially available polysaccharides such as curdlan, schizophyllan, and scleroglucan, exist in triple stranded helix structures. The interior of the helix structure is hydrophobic and the exterior is hydrophilic. This structure might be considered to be an extended version of a cyclodextrin. The triple helix structure is favored in aqueous mixtures but it can be denatured to a random coil structure by dissolution in polar aprotic solvents. The helix can be reassembled by exchanging the solvent back to water and it is this reversable process which has been recently employed to wrap the polysaccharide around other materials which are hydrophobic and fibrous (one dimensional) and thus modify their properties. In addition, this “sugar-coating” should improve biocompatibility. 
Also note that the β-1,3-glucan structure is stable in the human system due to a lack of enzymes available to degrade it and offers utility in medical/health applications.
Carbon nanotubes have very impressive mechanical properties and electrical conductivity and are at the forefront of new materials in nanotechnology. Processing and use of carbon nanotubes is limited by their hydrophobicity and agglomeration. A hydrophilic character can be incorporated onto the surfaces of the nanosized fibers by co-assembling, or wrapping, them with a β-1,3-glucan. Although chemical derivatization methods can also render them water soluble, mechanical and physical properties such as conductivity are adversely affected by the covalent structural changes. Modification by noncovalent means has minimal effect on the original nanotube properties. Thus, a polysaccharide-carbon nanotube complex is formed and water solubility is achieved by treating an aqueous suspension of nanotubes with a solution of a β-1,3-glucan such as schizophyllan in DMSO. The schizophyllan backbone was further derivatized to append groups that can interact with a high specificity with other biological molecules. This design is proposed for use as a sensor in a recent patent application (“Polysaccharide-Carbon Nanotube Complex,” M Mizu, S Shinkai, T Hasegawa, M Numata, T Fujisawa, K Sakurai, US Patent Application 20080242854, 2008 [full text]). A similar approach has been used by these authors to wrap polyaniline and polythiophene to produce nanofibers with good conductivity. Most recently, carbon nanotube fibers have been wrapped by β-1,3-glucan which had been derivatized with either cationic or anionic functional groups. Combination of these two complementary materials yielded self-assembled hierarchical architectures of different shapes depending on their ratio (“Creation of Hierarchical Carbon Nanotube Assemblies through Alternative Packing of Complementary Semi-Artificial β-1,3-Glucan/Carbon Nanotube Composites,” M Numata, K Sugikawa, K Kaneko, and S Shinkai, Chemistry - A European Journal 2008, 14, 2398 – 2404 [abstract]).
Although these discoveries are very far from large scale commerciallization, they illustrate a unique property (the reversible helix formation and incorporation of hydrophobic structures into its interior) of readily available β-1,3-glucan polysaccharides that may prove useful in other applications.
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August 2008 - Controlled-release systems based on a hydrophilic matrix
Too much of a good thing can have unintended consequences. This is true in pharmaceutical applications and in applications involving herbicides, biocides, personal care products, fragrances, even toilet cleaning products, where a large dose of the product can be 
harmful, expensive, or produce some other undesirable sensory effects. Thus, controlled, or sustained, release technology has evolved. Polymeric materials play an important part in these products due to their physical and mechanical properties which facilitate the holding and then releasing of active ingredients in a controlled fashion. Biobased, polysaccharide materials, such as cellulose ethers, have proven to be especially useful and a large commercial market continues to grow. Cellulose ethers are produced in many structural variations: different alkyl ether substituents (methyl, hydroxypropyl, hydroxyethyl, ethyl, and carboxymethyl being the most commercially important) in homogeneous or mixed compositions, of varying degrees of substitution and molecular weights. Although the most important materials are semi-synthetic (produced by derivatization of cellulose with alkyl halides or epoxides), a large fraction of the material nevertheless is derived from naturally occurring, renewable cellulose.
Recent progress in the understanding of controlled release processes is seen in a study of the diffusion mechanism of active ingredients in cellulose ether-based tablets. more...
June 2008 - Improving the biocompatibility of synthetic polymers by incorporation of hyaluronic acid
Synthetic polymer chemistry continues to provide us with amazing materials for just about every application imaginable. One of the current frontiers in which synthetic materials are being employed is at the interface with biological systems, that is, to replace damaged or failing tissues in living organisms, especially humans. Often the desired functional properties, such as strength and flexibility have been achieved, however longer term biocompatibility remains to be a challenge. For example, articles made from synthetic polymers which are used in the blood stream, such as vascular grafts, develop thrombosis in which platelets and red blood cells adhere to the unnatural material and form clots. Similarly, contact lenses made from synthetic materials can be fouled by adsorption of proteins that occur in tear fluids and cause discomfort to the wearer. There are many naturally occurring polymers that do not suffer these biocompatibility problems however they are not easily produced, especially in a “tailorable” way with a range of properties or with the facile processability of synthetic materials. Recently, researchers have achieved hybrid materials with the best features of both biological and synthetic polymers. more...
Ultimately, articles used in biological applications may be produced entirely by biological means. But until we are able to meet that awesome challenge, careful engineering of hybrids of biological and synthetic polymers like those described above will provide valuable materials for these needs.
April 2008 - Environmentally friendly aqueous viscosified treatment fluids and breakers for oil drilling
A large market for polysaccharides is in the oil drilling industry.
Seems like an odd combination ... Isn't it ironic that renewable
materials, polysaccharides, are used to facilitate production of a
depleting material, petroleum? What makes polysaccharides so valuable
in this application is the high viscosity of their aqueous 
solutions
and the ability to crosslink them to form shear-thinning gels (high
viscosity when the solution is at rest and low viscosity when being
pumped). Such viscous and visco-elastic treatment fluids are useful in
underground oil well operations for drilling, fracturing, diverting,
and gravel packing. That is, the treatment solutions are effective for
suspension of solids in drilling muds, removal of drill cuttings, and
placement of gravel packs and proppants (particulate materials that
bridge pores in the rock formations to maintain oil flow). The high
viscosity also facilitates transfer of hydraulic pressure throughout
the formation and prevents undesired loss of the fluid into the
formation. Thus, the aqueous polysaccharide solutions provide a
spectrum of engineered well treatment fluids. In addition to these
valuable functional properties, other benefits are derived from the
green features of polysaccharides, such as their renewability, very low
toxicity, and biodegradability. Examples of polysaccharides that are
used in oil drilling are guar gum (and its derivatives, hydroxypropyl
guar and carboxymethyl guar), xanthan gum, scleroglucan,
carboxymethylcellulose, and other galactomannans, such as locust bean
gum. Whereas, the much higher purity grades of these polysaccharides
are used for more high valued products, such as food and personal care,
the lower purity grades are well suited for the oil industry and thus
allow full usage of all materials from polysaccharide production.
In many of the applications of well treatment fluids described above, it is also necessary to reduce the viscosity of the fluid when that property is no longer needed prior to oil production. Various methods have been developed to depolymerize the polysaccharide and thus reduce the viscosity by incorporation of “breakers”, such as acids, oxidants, and enzymes. more...
February 2008 - Surface modification of cellulose mediated by xyloglucan
Like teammates, xyloglucan and cellulose have complementary abilities and work together to achieve something that neither could do alone. In naturally occurring wood, xyloglucan binds tightly and specifically to cellulose fibers. Cellulose fibers by themselves have very impressive strength, but an even greater composite strength is achieved when the fibers are “glued” together with xyloglucan. Xyloglucan's interaction with cellulose has also been employed in industrial applications to improve the performance of textiles and paper. Recently xyloglucan has been exploited as a vector or anchor to introduce new functional groups to cellulose surfaces and alter its properties under mild and environmentally friendly conditions.
Xyloglucan (XG) is widespread in nature in plants but is most commonly
isolated from tamarind kernel powder (~60% XG) which is produced
commercially on a large scale. XG actually is a group of
polysaccharides defined generally as neutral, unbranched polymers of
glucose with xylose pendent groups. This chemical structure (see
Figure) is very similar to that of cellulose in that they both have the
same poly(b-1,4-glucopyranose) backbone. The xylose substitution
pattern along the backbone varys depending on the
natural source. Certain other monosaccharides are also
typically found attached to the xylose units. Whereas cellulose is
highly crystalline and water-insoluble, XG is readily water soluble.
However when XG is associated with cellulose as in wood, a strong
complex results as evidenced by the fact that XG cannot be extracted
from it with water. The complex can be broken however by extraction
with strong aqueous base. Details of the XG-cellulose relationship are
reviewed in a recent article along with creative new methods which
make use of XG as an anchor to introduce new chemical functional groups
to cellulose surfaces and modify its properties. more...
December 2007 - Cellulose acetate - an important biobased material in liquid crystal displays
It's very apparent that liquid crystal display (LCD) devices are
popular and
finding their way into more products everyday. Examples are displays
for computers, televisions, appliances, portable devices like
phones, GPS devices, and the original application .... watches. The
advantages of LCDs are light weight, 
compact size and low power
consumption - vast improvements over the previous cathode ray tube
(CRT) displays. LCDs have a complex construction and are a truly
amazing triumph of science and engineering [read more].
Within an LCD, light is transmitted through a liquid crystal cell
which is sandwiched between two polarizing plates. The polarizing
plates are protected by a transparent film which is composed of
cellulose acetate (more specifically cellulose triacetate or
triacetyl cellulose in which all three of the hydroxyl groups on each
glucose repeat unit is fully acetylated). It's ironic that
cellulose acetate, one of the oldest commercial polymers, plays a
crucial part in this high-tech electronics appication.
Cellulose acetate (CA) is produced by the synthetic derivatization of biologically produced cellulose. As such, it is one of the first synthetically modified, biobased polymers and has found wide utility. Acetylation of cellulose causes a dramatic change in properties. Cellulose is hydrophilic, highly crystalline, can't be melt processed due decomposition before its high melting point, and is poorly soluble in common solvents. CA is a hydrophobic, amorphous material that can be dissolved in common solvents or melted, especially after mixing with plasticizers, and can be readily processed into different forms for many applications. Its functional properties include: moisture resistance, optical clarity, high heat resistance (softening temperature), melt processability, high mechanical strength and toughness. These properties have made CA valuable in the following commercial applications: plastic articles (tool handles, eyeglass frames), cigarette filter material, water purification membranes, textile fibers (known as “acetate”), optical films. The latter application, specifically its use in LCDs, is becoming an especially important market for CA and driving increased production of this biobased material. Its combination of high clarity, isotropic transmittance (passes light equally in each direction), good moisture and temperature resistance, low cost, adhesion to high surface-energy polarizing films, and also its renewable raw material source make CA the material of choice. more...
November 2007 - If you could dissolve wood in a solvent what could you do with that solution?
Maybe ...
... Regenerate the
wood in a different form that isn't possible by
conventional methods, such as fibers, films, composites, or less
ordered material that could be more easily converted to
glucose for ethanol production.
... Modify
its chemical structure and properties, homogeneously, with
chemical reactions.
... Analyze it to study the
wood's composition without having to
first separate the components.
These are just some of the ideas that are being explored now that wood and other lignocellulosic materials have been found to be soluble in ionic liquids (ILs).
Wood is primarily composed of lignin and the polysaccharides, cellulose and hemicellulose. Hemicellulose is a class of relatively complex polysaccharides, i.e., containing multiple monosaccharide repeat unit structures and with side chains/branching, and whose structure varies with plant species. Lignin is a network (crosslinked) polymer with oxygenated phenylpropane repeat units. Wood, and other lignocellulosic biomass, are renewable and CO2-neutral resources, however processing of wood into other products is inefficient and often involves hazardous and environmentally unfriendly processes (e.g., production of paper, or purified cellulose and its derivatives). Recently, many biopolymers in their purified forms have been found to be soluble in highly polar ionic liquids. These include polysaccharides such as cellulose and chitin which otherwise are only soluble in certain relatively hazardous solvents. Wood itself has just recently been found to be soluble in certain ionic liquids. more...
October 2007 - "Molecular engineering" of alginate's structure leads to improved properties
Alginate is a versatile polysaccharide produced commercially from seaweed (20,000 tons/yr). It is primarily used as a thickener or gelling agent for aqueous mixtures (other applications). It thus affects the flow properties of a solution – its rheology. These properties are valuable in food preparations, pharmaceutical formulations, and specialized medical applications such as cell encapsulation. Alginate forms strong gels in the presence of divalent cations, particularly calcium, by way of ionic crosslinks between the polyanionic alginate chains. Thus, when an aqueous solution containing sodium alginate is mixed with a water-soluble calcium salt, the mixture forms a gel with elastic properties. Alginate's unique gelling properties result from its primary chemical structure. The polymer backbone is composed of two monosaccharide repeating units, mannuronate (M) and guluronate (G), which are isomers differing in configuration at the C-5 position (see figure). They can be present in different ratios and in different sized blocks of M or G units. The G-blocks form especially strong interchain crosslinks with calcium ions and are a large factor in the gel properties. Alginate from different seaweed sources has different M/G ratios and different M and G block lengths and, as commonly occurs with natural products, has additional heterogeneity due to varying growth conditions. Recently, researchers have developed a method to synthesize alginate compositions in a controlled fashion with relatively long G-blocks at varying M/G ratios and an absence of M-blocks. These materials formed gels which showed markedly improved performance over native alginates.
Figure. (Top) Mannuronate (M) and guluronate (G) structures. Note different configurations at C-5. (Bottom) Synthetic conversion of all-M backbone structure to alternating M-G and then G-blocks.
The structure of alginate was optimized to produce gel beads, or capsules, specifically for medical applications (cell encapsulation, tissue engineering) where strength, stability, and controlled, uniform porosity are important. It is very likely that lessons learned in this study will be valuable in alginate's industrial applications as well. more...
September 2007 - Orally-dissolving strips for delivery of drugs and flavors
Maybe you've seen them in your drug store – small packages
containing thin
strips of material that dissolve quickly in your mouth and deliver a
dose of drug, breath
freshener,
or vitamin. The base material is a water
soluble polymer that can be formed into a film of sufficient strength
and
flexibility, and most importantly, is safe to ingest. What
type of materials can do all this? You guessed it ...
polysaccharides. Some examples of film-forming, water-soluble,
ingestible polysaccharides are hydroxypropyl methylcellulose (HPMC),
carboxymethylcellulose (CMC), and pullulan.
Active ingredients, flavors, and colors can be absorbed into the polysaccharide film which provides a convenient means for packaging, dispensing, and ingestion. When contacted with saliva in the mouth, the film dissolves rapidly, releasing the ingredients. This form of delivery offers many advantages, especially for children and elderly people who have difficulty swallowing conventional pills. more...