Common biopolymers

The life cycle assessment (LCA) results of PLA, PHA, and thermoplastic starch (TPS) were the most prevalent biopolymers currently represented in the life cycle literature while there were other biopolymers marketed and in development, such as biobased 

Two other important plant-based materials in the polymer industry are biobased 

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The most commonly biopolymers separated by Fl-FFF are proteins [49]. Fl-FFF is capable of separating proteins differing by just 15% in size within 3 to 10 min. S-Fl-FFF has been applied to a variety of proteins, including albumin, ovalbumin, y-globulin, hemoglobin, ferritin, lysozyme, [1-casein, apoferritin, human and rat blood plasmas and elastin [41,240,247]. Fl-FFF was also used to investigate the structural transformations of proteins [240]. 

Table 8.5. 1 Elemental compositions of common biopolymers and plant materials ...

The genealogy of microorganisms is most clearly recorded in their common biopolymers, the amino acid sequence of homologous proteins and the nucleotide sequence of homologous nucleic acids. 

The most common biopolymers derived from animals are chitin and chito-san. Chitin is a macromolecule found in the shells of crabs, lobsters, shrimps, and insects. The primary unit in the chitin polymer is 2-deoxy-2-(acetylamino) glucose. Chitin can be degraded by chitinase. Chitosan is a modified natural carbohydrate polymer derived from deactylation of chitin, which occurs principally in animals of the phylum Arthropoda. Chitosan is also prepared from squid pens. Chitin is insoluble in its native form but chitosan, the partly deacetylated form, is water soluble. The materials are biocompatible and have antimicrobial activities as well as the ability to absorb heavy metal ions [16]. 

Polylactic acid (PLA) is the second common biopolymer that is produced by microbial fermentation. It is thermoplastic aliphatic polyester that can be synthesized from biologically produced lactic acid polymerized by ring opening polymerization. Lactic acid is a chiral molecule existing as two stereoisomers, L- and D-lactic acid, which can be produced by different ways, i.e., biologically or chemically synthesized [Averous, 2008). 

Unlike xenobiotic substrates, biopolymers such as cellulose have been in the eco-system for a very long time, allowing the evolution of efficient enzymatic pathways specific for the breakdown of these substrates. Common biopolymers therefore readily undergo biodegradation in a wide variety of environmental conditions ranging from aerobic compost heaps to anoxic deep-sea marine sediments. 

A biopolymer or bioplastic is a polymer produced by a living organism. Cellulose is the most common biopolymer constituting about a third of all plant biomass. All living things produce other biopolymers such as polynucleotides and proteins. An example of a class of useful biopolymers are the so-called bacterial polyesters that are harvested from bacteria grown under specific conditions. 

These materials are from renewable sources and are often made from plant materials that can be grown year after year and should come from agricultural nonfood crops. Biodegradable polymers are broken down into CO 2 and water by microorganisms. Although biopolymers may be able to help solve the disposal problems of current plastic packaging, it is not clear if they can really deliver on this promise and whether there is possible competition with the food chain. Cellulose is the most common biopolymer and organic compound on Earth. Other examples are starch, PHB (polyhydroxybutyrate), natural fibers, silk, and wood plastic composites (WPC). 

The PHA is produced by bacterial fermentation of sugar or lipids. Polymers in PHA family can be produced by 150 different monomers, due which a large variety of PH As can be synthesized with a wide range of properties. Polyhydroxybutyrate (PHB) is the most common biopolymer in PHA family. PHB is water insolirble and has good resistance to hydrolytic degradation. The and of PHB are approximately 175°C and 15°C respectively (Kumar et al., 2011). PHB exhibits low water permeabihty which is comparable to that of LDPE, and has similar thermal and mechanical properties as isotactic PP (Savenkova et al., 2000). 

A common feature of biopolymer adsorjition is that its rate is usually one to tliree orders of magnitude smaller than the diffusion-limited rate to a perfect sink ... 

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

At first glance, the contents of Chap. 9 read like a catchall for unrelated topics. In it we examine the intrinsic viscosity of polymer solutions, the diffusion coefficient, the sedimentation coefficient, sedimentation equilibrium, and gel permeation chromatography. While all of these techniques can be related in one way or another to the molecular weight of the polymer, the more fundamental unifying principle which connects these topics is their common dependence on the spatial extension of the molecules. The radius of gyration is the parameter of interest in this context, and the intrinsic viscosity in particular can be interpreted to give a value for this important quantity. The experimental techniques discussed in Chap. 9 have been used extensively in the study of biopolymers. 

There are approximately 20 common naturally occurring amino acids, hence 20 different R groups that appear as pendents on the polyamide chain. Many other amino acids have been isolated or prepared, each representing a variation in R. The number of isomeric stmctures is myriad. Protein biosynthesis is mediated by other biopolymers, the nucleic acids. 

Immobilized Enzymes. The immobilized enzyme electrode is the most common immobilized biopolymer sensor, consisting of a thin layer of enzyme immobilized on the surface of an electrochemical sensor as shown in Figure 6. The enzyme catalyzes a reaction that converts the target substrate into a product that is detected electrochemicaHy. The advantages of immobilized enzyme electrodes include minimal pretreatment of the sample matrix, small sample volume, and the recovery of the enzyme for repeated use (49). Several reviews and books have been pubHshed on immobilized enzyme electrodes (50—52). 

TSK-GEL PW type columns are commonly used for the separation of synthetic water-soluble polymers because they exhibit a much larger separation range, better linearity of calibration curves, and much lower adsorption effects than TSK-GEL SW columns (10). While TSK-GEL SW columns are suitable for separating monodisperse biopolymers, such as proteins, TSK-GEL PW columns are recommended for separating polydisperse compounds, such as polysaccharides and synthetic polymers. 

Interestingly, it was in a different context that both Seebach and Gellman approached the field of yS-peptides. Seebach s initial interest in yS-peptides stemmed from their resemblance to poly(yS-hydroxy alkanoates) (PHA), an ubiquitous class of biopolymers of which poly[(P)-3-hydroxybutanoic acid] (8, PHB) is the most common (for reviews see [37, 38]). 

Saudek V, Pivcova H, Drobnik J (1981) NMR-study of poly(aspartic acid). 2. Alpha-peptide and beta-peptide bonds in poly(aspartic acid) prepared by common methods. Biopolymers 20 1615-1623... 

Polymers are substances whose molecules are very large, formed by the combination of many small and simpler molecules usually referred to as monomers. The chemical reaction by which single and relatively small monomers react with each other to form polymers is known as polymerization (Young and Lovell 1991). Polymers may be of natural origin or, since the twentieth century, synthesized by humans. Natural polymers, usually referred to as biopolymers, are made by living organisms. Common examples of biopolymers are cellulose, a carbohydrate made only by plants (see Textbox 53) collagen, a protein made solely by animals (see Textbox 61), and the nucleic acid DNA, which is made by both plants and animals (see Textbox 64). 

MnP is the most commonly widespread of the class II peroxidases [72, 73], It catalyzes a PLC -dependent oxidation of Mn2+ to Mn3+. The catalytic cycle is initiated by binding of H2O2 or an organic peroxide to the native ferric enzyme and formation of an iron-peroxide complex the Mn3+ ions finally produced after subsequent electron transfers are stabilized via chelation with organic acids like oxalate, malonate, malate, tartrate or lactate [74], The chelates of Mn3+ with carboxylic acids cause one-electron oxidation of various substrates thus, chelates and carboxylic acids can react with each other to form alkyl radicals, which after several reactions result in the production of other radicals. These final radicals are the source of autocataly tic ally produced peroxides and are used by MnP in the absence of H2O2. The versatile oxidative capacity of MnP is apparently due to the chelated Mn3+ ions, which act as diffusible redox-mediator and attacking, non-specifically, phenolic compounds such as biopolymers, milled wood, humic substances and several xenobiotics [72, 75, 76]. 

Now, most metal ion/organic molecule chemical reactions inside cells also come to equilibrium rapidly. The organic products, made irreversibly available by synthesis under feedback control, contain a broad set of possible binding sites for selected metal ions mainly in soluble proteins (enzymes) and in the pumps for uptake or rejection managed at the cell membrane, as well as in the factors, transcription factors, necessary for controlled production of those organic products under the direction of the coded system. These ion-selective binding sites are common to all cells so that while all cells are based on similar major organic reactions and similar but specific biopolymer products, they also have in common a set of... 

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