Microbial production of biodegradable polymers and their role in cardiac stent development

Biodegradable polymers have attracted a lot of attention in the recent years. These biopolymers are large macromolecules composed of single, repeating monomer units. They are of very high molecular weight and their material characteristics vary according to the nature of their monomer composition. Over the last decade, depletion in the petroleum reserves has resulted in the emergence of biodegradable polymers as a potential alternative to the traditional plastics [1]. Also, increased production of these plastics has proven to be a serious threat to the environment. Being non biodegradable in nature, their disposal has raised major concern. Hence, biodegradable polymers are considered to be a potential solution. Apart from being biodegradable, some of these biopolymers are also biocompatible in nature and can be easily processed to be used for various applications. Hence, their applications range from being used in the packaging industry, chemical industry, agriculture and medicine. Considering these facts, large scale production of these biodegradable polymers and their extensive use is critical both to ensure alternative sources of plastic and also for the environment [2]. These biodegradable polymers can be grouped into two different classes i.e. natural and synthetic polymers. The former are obtained from natural sources and the latter require chemical synthesis. Natural polymers can be further classified into four different classes depending on their sources including agricultural, animal, marine and microbial sources. Those that are derived from the agricultural sources include polysaccharides, proteins and lipids which in turn include starches, lignocellulosic products such as pulp, and pectin. Biopolymers derived from animal sources are gelatin and collagen while marine sources are able to produce chitin which is processed into chitosan. Polymers derived from the microbial sources include polyhydroxyalkanoates (PHA) and polylactic acid (PLA). Polyhydroxyalkanoates are produced completely by microbial fermentation whereas polylactic acid is partially synthesised. The monomer, lactic acid, is produced by microbial fermentation and then polymerised using chemical catalysis. Natural polymers can be completely degraded by the microorganisms and degradation involves enzymatic scission of the polymer chain. The truncated polymer chain is later metabolized. Synthetic polymers on the other hand can be synthesised using bio derived monomers or synthetic monomers (precursors) derived from petroleum products [1]. In this chapter, microbial biopolymers, their production and their role in cardiac stent development will be discussed in detail.