**2. Polyhydroxyalkanoates**

Bio-polymers such as polyhydroxyalkanoates (PHAs) are produced by microorganisms as lipid inclusions for granular types of energy storage inside the cellular structure [17]. PHAs are natural polyesters made from thermoplastic 3-, 4-, 5-, and 6 hydroxy alkanoic acids. More than 90 genera of bacteria, both Gram-positive and Gram-negative, have been found to produce PHAs in both aerobic and anaerobic conditions thus far. Some native bacterial strains, recombinant bacterial strains, and recombinant eukaryotes can all manufacture polyhydroxyalkanoates (PHAs). These bio polyesters are created by metabolically converting different carbon sources.

Numerous PHA polymers also offer intriguing characteristics, such as the ability to biodegrade, and they can be used for a variety of purposes, from single-use bulk plastics to specialized medicinal applications [18].

### **2.1 Structure of PHA**

A total of 150 distinct PHA congeners have been identified. The resulting polymer is known as polyhydroxybutyrate or polyhydroxybutyric acid if the group is R = CH3, polyhydroxyoctanoate (PHO) if R = C3H7, and so on.
