Biological Sources, Chemistry, and Extraction of Biopolymers

To foster a green environment, considerable efforts have been made to replace synthetic polymers with biodegradable materials, such as biopolymers, particularly for the development of green drug delivery systems. Biopolymers are a prominent class of functional materials with high-value applications, generated either by biological systems or derived from biological sources. Natural sources of biopolymers include plants, animals, microorganisms, and agricultural wastes. Biopolymers exhibit excellent properties, including flexibility, tensile strength, stability, reusability, and many more. Biopolymers are composed of repetitive monomers bound covalently via polymerization reaction or enzyme-catalyzed assemblies of monomeric units that occur in the biosynthetic pathway within biological systems. Biopolymers can be classified based on their source, chemical composition, functional properties, degradability, type of charges, and other factors. The extraction of biopolymers involves a range of chemical and enzymatic processes that vary specifically for each biopolymer. Some of the extraction methods include the use of coagulating agents, hydrolysis, alkali and acid treatments, bleaching, deproteination, and demineralization, among others. Following extraction, purification, and often modification, biopolymers are prepared for potential applications. Due to their renewability, abundance, biodegradability, and unique properties, such as higher absorption capabilities and ease of functionalization, biopolymers have been explored for various industrial applications. This chapter examines the sources, chemistry, and extraction procedures for several important biopolymers, including polyhydroxyalkanoates, polylactic acid, chitosan, alginate, polyesteramide, starch, gelatin, polyglycolic acid, and pectin, as well as their biomedical applications.