Abstract
Bacterial biodegradable plastic, polyhydroxyalkanoates (PHAs) composed of hydroxy fatty acids, are carbon storage intracellular polymers synthesized by various bacteria and archaea. These carbon storage polymers are accumulated as water insoluble cytoplasmic nano-sized inclusions in response to nutrient limitation and degraded when limiting nutrient is supplied again. The PHA particles are spherical and composed of a polyester core surrounded by phospholipids and proteins. The key enzymes of PHA biosynthesis and particle formation are the PHA synthases, which catalyze the formation of PHA. Various metabolic routes have been identified and established in bacteria to provide substrate for PHA synthases. Based on their functions, the genes which encode these PHA synthases are grouped into pha biosynthetic, regulatory, and granule associated proteins and depolymerizing genes. In most of PHA producing bacteria, pha genes especially biosynthetic genes are colocalized in operons but not under transcriptional control of a single promoter and diversity is there in this respect. Bacterial PHAs are currently considered as biocompatible and biodegradable biomaterials with numerous potential applications particularly in medicine, medical and packaging. Thus offering a solution for the existing ecological and environmental problems caused by conventional plastic and petroleum-based products.
