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 different applications. Plastics were first used in packaging and housing materials. Later plastics find their way into medicinal, pharmaceutical and industrial applications. Today, plastics applications have either totally or partly substituted the other materials used previously in industrial applications (on all or some of their parts) such as wood, mud, metals, glass and other materials [35, 36]. Plastic is the best choice in many applications because of its low cost, stability, durability, good mechanical and thermal properties. Those who are interested in the materials produced by biopolymers and are investing funds and arranging resources aimed at commercializing species of biopolymers should identify the areas which lead to the success of the plastic applications. That will enable a successful start for any of the biopolymer application species still out of the market because of the value of the synthetic polymer. Some of the important biopolymer species, such as the bioplastc polyhydroxyalkanoates, gum Arabic, agar, alginate and so on, already exist in the market [28, 35, 37].
2.1.7 Biopolymer Commercialization
As well as plastics and bioplastics, the other types of biopolymer were given more opportunities and many of them were commercialized. Biopolymers have unique properties (there are some exceptions); they are produced and degraded through the biological system, therefore they are non-toxic (mostly); they are bioavailable (mostly); They are diverse, applicable, and renewable. There are many types of classifications which are based on their chemical, biological and physical properties; their source (plant, animal and microbes); their applications (medicinal, pharmaceutical, agriculture, industrial); their economic value; their biodegradability (biodegradable, non-degradable); their bioavailability; their cost and their mechanical properties. In this chapter, the classification which is based on the polymer chemical structure will be used. The main limiting factor in commercializing biopolymers is their production cost. For that this chapter will use the classification which is based on the polymer chemical structure [35].
2.1.8 The Eight Different Biopolymers
The eight types of biopolymers are: (1) nucleic acids (DNA and RNA); (2) polyamides which are polymers containing repeated amide groups (protein poly-(amino acids) such as, gelatine, casein, wheat gluten, silk and wool); (3) polysaccharides, any of a class of carbohydrates whose molecules contain chains of monosaccharide molecules (such as, starch, cellulose, lignin, chitin); (4) organic polyoxoesters (such as poly(hydroxyalkanoic acids), poly(malic acid) and cutin); (5) polyisoprenoides (such as natural rubber or gutta-percha [a whitish rubber derived from the coagulated milky latex of gutta-percha trees; used for insulation of electrical cables]); (6) inorganic polymers such as inorganic polyesters with polyphosphate, (7) polyphenols (such as lignin or humic acids), and (8) polythioesters, for example, poly(3-mercaptopropionate). Polymers from bioderived monomers could be polymerized and might be added as group nine. Additionally, some inorganic elements might show accumulation in the microbial cells in repeated forms but due to their nature they form crystals which are usually different to those made in labs. For example, magnetotactic bacteria show Fe3O4 chains of similar crystals which are unique in their structures. The helical twist of the Fe3O4 series of crystals are not cubes. It might be interesting to report that similar structures are found in goethite in the strengthening of limpet teeth. Other examples are iron, sulphides, pyrite crystals found in some anaerobic bacteria. In fact, more research should be conducted on the nature of the inorganic structures which might be finally classified as biopolymer because they are not crystalline spontaneously but due to the effect of proteins and enzymes. The amazing structure of different diatoms might be a good example [35, 38, 39].
2.2 Biopolymer Type Number 1: Nucleic Acids
Nucleic acids are the genetic code in living cells. DNA and RNA are the most important biopolymers that are located in the nucleotides of the eukaryotic cells and in the cytoplasm of the prokaryotic cells [40, 41]. DNA and RNA are polymers in their nature. They are usually used in various genetic manipulation tools, as well as in some fine technical applications and nanoapplications. DNA is used to generate new protein through mutagenesis, which gives new protein and thus new function or products (protein engineering). RNA is made from polymers of ribose sugar, phosphate and nitrogenous base. DNA is made from polymer of deoxyribose sugar, phosphate and nitrogenous base. DNA was used as a platform based on self-assembled DNA biopolymer for high-performance cancer therapy [42]. DNA novel nanomaterial is designed for applications in photonics and in electronic [43, 44].