Biopolymers starch

Polymers are macromolecules built of smaller units called monomers. The process by which they are formed is called polymerization. They may be synthetic (nylon, Teflon, and Plexiglas) or natural (such as the biopolymers starch, cellulose, proteins, DNA, and RNA). Homopolymers are made from a single monomer. Copolymers are made from two or more monomers. Polymers may be linear, branched, or cross-linked, depending on how the monomer units are arranged. These details of structure affect polymers properties. 

The major classes of biopolymer, starch and starch blends, polylactic acid (PLA) and aliphatic-aromatic co-polyesters, are now being used in a wide variety of niche applications, particularly for manufacture of rigid and flexible packaging, bags and sacks and foodservice products. However, market volumes for biopolymers remain extremely low compared with standard petrochemical-based plastics. For example, biopolymer consumption accounted for just 0.14% of total thermoplastics consumption in Western Europe for 2005. 

There is only one example which makes use of a biopolymer, starch, imprinted with a dye [60]. Methylene Blue could be adsorbed on starch which was crosslinked with cyanuric chloride to almost 100% with respect to the concentration of theoretically available binding sites. The blank adsorbed a mere 17% under identical conditions. It is estimated that 7-8 glucose units form a single cavity for the template, somewhat reminiscent of a- or P-cyclodextrins, but shape selectivity has not been investigated. It seems remarkable but these investigations seem to have been initiated without any awareness of the earlier work on imprinting. 

Nantes was chosen as the location because of its INRA Research Centre, which is renowned for its basic and applied research on plant biopolymers, starch, proteins and cell wall polysaccharides. The main objectives of the Nantes Centre in Plant Science first of all concerns the biosynthesis of macromolecules and assemblies in planta, secondly their structural characteristics and related physico-chemical and functional properties, and thirdly with their behaviour in multiphasic systems in relation to end-uses in food and non-food applications. In addition, human nutrition is also considered. 

One of the novel applications of biopolymers, which do not fit into any of the previous categories, is its use in modifying the food textures, e.g., gelatin-based biopolymer starch fat replacers possess fat-like characteristics with smoothness and short plastic textures that remain highly viscous after melting. Research is... 

Aggarval P, Dollimore D., Heon K. Comparative thermal analysis study of two biopolymers, starch and cellulose, J Thermal Ana. 50 (1997) 7. 

Starch cross-linked with epichlorohydrin reacted with AW-diethyl-2,3-epoxy-propylamine to form an ion-exchange material that is suitable for the fractionation of polysaccharides and other biopolymers. Starches cross-linked with either epichlorohydrin or phosphorus oxychloride adsorb ot-amylase. ... 

Starch-based foams can be prepared from different starch sources, with 70% of the polystyrene being replaceable with biopolymer starch. Functional starch-based plastic foams can be prepared from different starch sources, depending on their availability. 

Glucose A 6-carbon sugar molecule, which is the building block of natural substances like cellulose, starch, dextrans, xanthan, and some other biopolymers and used as a basic energy source by the cells of most organisms. 

Dextran gels have been utilized since the late 1950s (1) for the separation of biopolymers. First attempts on Sephadex (2-5) and Sephadex/Sepharose (6-8) systems are documented for hydrolyzed and native starch glucans. Up until now, particularly for the preparative and semipreparative separation of polysaccharides, a range of efficient and mechanically stable Sephacryl gels (9-14) have been developped. 

The performance of several Sephacryl gel combinations is illustrated by results achieved for glucans from different types of starch granules. The applied Sephacryl gels of Pharmacia Biotech (15) are cross-linked copolymers of allyl dextran and N,N -methylene bisacrylamide. The hydrophilic matrix minimizes nonspecific adsorption and thus guarantees maximum recovery. Depending on the pore size of the beads, ranging between 25 and 75 im in diameter, aqueous dissolved biopolymers up to particle diameters of 400 nm can be handled. 

Biopolymers derived from biomass such as from agro-resources (e.g., starch, lingo-ceUulosic materials, protein and lipids)... 

Biopolymers have diverse roles to play in the advancement of green nanotechnology. Nanosized derivatives of polysaccharides like starch and cellulose can be synthesized in bulk and can be used for the development of bionanocomposites. They can be promising substitutes of environment pollutant carbon black for reinforcement of rubbers even at higher loadings (upto SOphr) via commercially viable process. The combined effect of size reduction and organic modification improves filler-matrix adhesion and in turn the performance of polysaccharides. The study opens up a new and green alternative for reinforcement of rubbers. 

As discussed in previous sections, sugars, starch and (ligno)cellulose can be converted into ethanol by fermentation, the latter via preliminary chemical and physical pretreatment followed by enzymatic breakdown of the biopolymers. Pure ethanol can be added to gasoline or diesel. However, this requires an energy-intensive distillation step. This and the energy used in fertilizers, transportation... 

Different routes for converting biomass into chemicals are possible. Fermentation of starches or sugars yields ethanol, which can be converted into ethylene. Other chemicals that can be produced from ethanol are acetaldehyde and butadiene. Other fermentation routes yield acetone/butanol (e.g., in South Africa). Submerged aerobic fermentation leads to citric acid, gluconic acid and special polysaccharides, giving access to new biopolymers such as polyester from poly-lactic acid, or polyester with a bio-based polyol and fossil acid, e.g., biopolymers . 

FIGURE 5.9 DSC profiles of potato starch at different water contents (volume fraction of water indicated next to each profile). Heating rate=10 °C/min. Donovan (1979), Phase transitions of starch-water system. Biopolymers, 18, 263-275. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission. 

Donovan, J. W. (1979). Phase transitions of the starch-water system. Biopolymers 18,263-275. 

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