9.1 Introduction

Traditional applications of synthetic polymers are mostly based on their inertness to environmental degradations (hydrolysis, oxidation, biodegradation, and so on). The rapid increase in the volume of use of synthetic polymers has contributed to the solid waste management problems in recent years. Total management of polymer wastes requires complementary combinations of recycling, incineration for energy, and biodegradation [1]. Polymers prepared from renewable and sustainable resources can be easily designed, synthesised, and engineered by environmentally compatible routes and can be disposed after use by biodegradation (composting, etc.) [2-6]. Biodegradable polymers are necessary in the design, synthesis and applications of biomedical implants and drug release systems. Among those received increasing attention since 1970s are aliphatic polyesters such as microbial polyhydroxybutyrate (PHB), and its copolymers [7, 8] and polylactic acid (PLA), and its copolymers [9-12].

PHB is the energy storage material for certain bacteria and efforts to commercialise it and its copolymers as structural and package materials have not been successful due to their high costs and the difficulty in thermal processing. PLA from the polymerisation of lactic acid, a fermentation product of low cost polysaccharides, is a product which is produced from a combination of biotechnology and chemical technology. PLA and its copolymers are the subjects of this review. There have been many reviews published recently, especially related to the biomedical application areas, and thus only major current work is covered here.

9.2 Synthesis