Since 1940, the most widely used plastics have been polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), and poly(vinyl chloride) (PVC). Despite advances, plastics processing and manufacturing generate two major problems: the use of nonrenewable resources to obtain their raw materials and large quantities of waste generated for disposal.

Biodegradable plastics degrade completely within three to six months when attacked by microorganisms, depending on the environmental conditions. The polyhydroxyalkanoates (PHAs) are natural polyesters consisting of units of hydroxyalkanoic acids with similar prop­erties to petrochemical plastics (Jau et al., 2005).

The polyhydroxyalkanoates are produced as a reserve of carbon and energy accumulated within the cells of various microorganisms such as microalgae. Among the PHAs, polyhydroxybutyrate (PHB) and its copolymer polyhydroxybutyrate-co-valerate (PHB — HV) are synthesized by cyanobacteria when exposed to specific conditions of cultivation (Sharma et al., 2007).

The degradation rate of PHB and PHB-HV depends on many factors, some related to the environment, such as temperature, moisture, pH, and nutrient supply, and others related to the biopolymer itself, such as composition, crystallinity, additives, and surface area. Due to its physical and chemical properties, PHB is easily processed in equipment commonly used for polyolefins and synthetic plastics (Khanna and Srivastava, 2005).