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2 Natural Polymer Types and Applications
Amro Abd Al Fattah Amara1,2
1Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications, Alexandria, Egypt
2Head of Scientific Publishing office, City of Scientific Research and Technological Applications, Alexandria, Egypt *Corresponding author: [email protected]
2.1 Introduction
The first to use biopolymers (non-fibrous biopolymers) in a technical application were the ancient Egyptians (The Pharaohs), who used gum (later named gum Arabic or Acacia gum) (Figure 2.1) before the second millennium BC [1–3]. The Pharaohs were known to use the Arabian Gum and other plant glue in preparing inks used in writing, to install and fix colors and to prepare papyrus (the material upon which the ancient Egyptians wrote) (Figure 2.2). Papyrus was formed by cutting the stem a tall rushlike plant (Cyperus Papyrus) of the Sedge family, growing in Egypt, Abyssinia, Syria, Sicily, etc.), into thin longitudinal slices, which were gummed together and pressed. Gum Arabic was also used to prepare different treatments used in many therapeutic and protective combinations. The resin was used in the mummification process, which included soft tissue removal, dehydration of the body, embalming, sealing inside and outside with resin, covering with bandages and preserving in an evacuated sealed chamber and in a dry place [4]. Apparently, they recognized that gums and resins protect plants from spoilage and so they invented a gum/resin sealing strategy. They used it in most of the applications where an adhesive was required. Gum Acacia or gum Arabic was also used by the ancient Egyptians as a food. The ancient Indian, Chinese, Greeks, Romans, and many other ancient civilizations have also used the gum and resin in different applications. Biopolymers have unique properties, which made them the best choice in various applications. They are in most cases, biodegradable, bioavailable, biocompatible, non-toxic, environmentally friendly, applicable, diverse, and have many other useful properties [5–14]. They also degrade to safe structures. Most of the biopolymers are produced by plants but some are produced by animals, algae and microbes.
Figure 2.1 Gum Arabic; the first known biopolymer, its name comes from the Arabic merchants who sold it in Europe. It is still sold nowadays in local markets as big colored transparent granules.
Figure 2.2 Acacia tree as drawn and memorized by ancient Egyptian civilization.
2.1.1 The Monomer, Polymer and Biopolymer
Polymer is the generic name for a species of macromolecules which have the unique properties of repeated monomers, a linear or branched backbone or a naturally occurring or synthetic compound consisting of large molecules made up of a linked series of repeated simple monomers. In contrast, a monomer is a simple compound whose molecules are joined to form polymers. The monomeric constituents of the polymer are responsible for their properties. They either have the same chemical structures, in such cases the polymer is named a homopolymer, or they are different in their chemical structures and the polymer is named heteropolymer. The more monomers with different properties the polymer has the the wider its range of physicochemical and biological activity might be. For example, different proteins consist of different amounts and sequences of 20 amino acids. Repetition of different constituents of amino acids gives each protein its unique specificity.
2.1.2 The Monomeric Structure
Why are some polymers nearly inert while other are so dynamic? [15, 16] Why are they different? Why are some of them grouped in a certain ways? It is, of course, because of their structure which depends on their monomeric subunits [17–21]. As an example, protein varies in their monomeric types (amino acids), numbers and location. So, each protein is unique in its structure/function/specificity [22–24].
2.1.3 Enzymes (Protein Polymers) Building Polymers
The sequence of polymer building in the cells starts from the DNA and the protein. Life must be started by the existence of many biological and chemical forms including both DNA and protein which are highly complicated polymers, not only in their components, but also in their design and the large amount of information installed which gives one the code and the other the dynamicability. Proteins alone are inactive structures, but if other elements exist (e.g., ions, water, pH, etc.) the requrement that enable them to react as biologically active and dynamic macromolecules with high specific reaction are satisfied.
Accumulation of mutants causes change in the protein function. Mutants in the cell cycle, repairing or apoptosis genes might turn normal cells to cancer cells. One important example is DNA and the RNA polymerases. DNA is a long linear polymer; found in the nucleus of a eukaryotic cell or in the cytoplasm of the prokaryotic cells and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information. RNA is a single strand long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of the eukaryotic cell. The polymerases which work on them are different. The polymers represent essential and vital parts of the cells such as the DNA, RNA and protein. Additionally, they can be used as storage components such as starch, polyhydroxyalkanoates, etc. They can also be used by the cell for different purposes, for example as a protective agent (e.g., alginate, gums, and resin).
Biopolymers are different from the synthetic polymers in two main ways in that they are produced by living cells (produced naturally) and that they can be used by their main producer or by related or different kinds of the living cells (naturally biodegradable: capable of being decomposed). Generally, they belong to the biological system and their polymeric structure, the polymerization steps, and their degradation is done through various enzymatic activities. In other words they are a globally essential part of the biological system, produced by it and also degraded through it. For that it is normal to find a polymer produced by a microbe and degraded by the same microbe. More simply, it is a polymer for us, but it is a food or a part of the cell’s different structures for their producer. Their presence is governed by the biological aspects [25, 26]. As they from the biological system, their elements in most cases (except structures like native foreign protein and the LPS) are compatible with the human immune system [25, 27–31]. In some instances they are named white or green to demonstrate their compatibility with the biological system or their safety to nature [8, 28, 32, 33].
2.1.4