ABSTRACT
Plastic industry has been one of the fastest growing sectors of the world economy. This is because plastics are utilized in almost every manufacturing industry from automobiles to medicines. A majority of synthetic plastic polymers are extremely resistant to microbial attack due to their high molecular weight, high number of aromatic rings, unusual bonds or halogen substitutions (Alexander, 1981). For this reason, a large accumulation of plastic waste in the biosphere has given rise to the problem of severe environmental pollution. Over past three decades, a great deal of intensive efforts has been made upon the preparation of environmental friendly polymers, which can be easily degraded by microorganisms. As a result, many types of aliphatic polyesters including polyhydroxyalkanoates (PHAs), poly (ε-caprolactone) (PCL), and poly (Llactides) (PLA) have been developed as biologically recyclable green polymers (Scott, 2000; Muller et al., 2001; Shimao, 2001). The biodegradable plastics, as novel materials make claims to be environmentally friendly. In order to find an alternative material, researchers have developed fully biodegradable plastics, such as polyhydroxyalkanoates (PHAs) (Verlinden et al., 2007). Until today, more than 300 microorganisms are known to synthesize and intracellularly accumulate PHA (Lee et al., 1999). The production of PHA (SCL) has been studied extensively using many microorganisms viz. Cupriavidus necator, Bacillus cereus, Alcaligenes lactus, Azotobacter vinelandii, Methylobacterium sp., recombinant Escherichia coli (Lee, 1996) and in few halophilic microorganisms including Halomonas sp. while the production of medium chain length PHAs have been mainly focused on Pseudomonas sp.
