href="#ulink_70eea717-1e7b-57d6-a703-71f9623aa278">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 The Synthetic Polymers are Non-homogenized with Nature
The synthetic polymer produced chemically through specific chemical reactions or from petroleum oil and their monomers are linked together to form large molecules. They are macromolecules made of linked series of repeated monomers joined by chemical bonds through chemical reactions, mainly polymerization, polycondensation and polyaddition. The polymerization process, in most cases, contains compounds toxic to the live cells. While the biopolymer is compatible with nature, the synthetic polymer is incompatible. This incompatibility was first considered a revolution. The synthetic polymer, in most cases, is undegradable. For example, the invention of durable plastic was considered a revolution at the time of its discovery; however, this image has changed over time. Plastic (and its products) is either a synthetic or semisynthetic material that can be molded or extruded into objects, films, filaments or be used to make structures such as coatings and adhesives. Their accumulation as waste is causing great concern. Millions of tons each year are discarded and accumulated in the earth, which causes affects from the ground through to the ozone layer (the plastic byproducts and the gases produced either through production processes or after its burning). Today nobody could guarantee that 100% of polymerization step(s) are free from toxic chemical compounds and stable against the natural, physical or chemical degradation.
2.1.5 The Competition between Biopolymers and Chemically Synthetic Polymers
The plastic revolution brings wealth and happiness for many and allows nearly all industrial sectors to flourish, but nowadays it is a subject for continuous evaluation and validation. However, the image is not entirely black, in fact there are many positive things that compete strongly and direct us toward better management of our resources: are we are able to reduce the amount of synthetic polymers? Are we are able to fill the market demand? In fact, biopolymers are not able to do that today. Some points could be summarized:
1 The synthetic polymers are mostly hydrocarbons. Some powerful microbes are able to degrade them successfully such as Pseudomonas aeruginosa and the different Gordonia spp [34].
2 There are a huge number of biopolymer products and types that could be used as alternatives to synthetic polymers. An example of biopolymers that could be polymerized, which have similar or better properties to the natural products are the polyhydroxyalkanoates. They is considered to be alternatives to plastic. Another example is natural rubber which is an alternative to synthetic rubbers.
3 The recycling of synthetic polymers is under continuous quality control and validation and has reduced the global demand for the amount produced annually.
4 There is an increasing worldwide awareness concerning the plastic accumulation problem and global pollution.
5 Investment in natural materials is profitable.
6 There is a rising political awareness in the problems caused by synthetic materials after the many side effects.
7 Not all synthetic materials have the same issues at the same level. Some forms are beneficial and their side effect could be avoided.
2.1.6 The Plastic Success
The most well know polymers are plastic(s); this is a generic name for synthetic, semisynthetic or natural materials that can be molded or extruded into objects, films, filaments or be used to make, for example, coatings and adhesives. Synthetic plastic is mainly derived from petroleum oil or through chemical reactions. But there are a considerable number of plastics that have a biological origin. Because of their perfect mechanical properties, different types of plastic were formulated to match
