*2.1.2 Polyhydroxyalkanoate (PHA)*

PHA is a microbial polymer which retains close properties to non-biodegradable thermoplastics such as LDPE, as shown in **Table 2** [27]. Its discovery and synthesis began during the early twentieth century [22]. It possesses desirable physical and mechanical characteristics such as high melting temperature; the tensile strength is slightly higher than that of LDPE with an average of 21 MPa. Unlike the aforementioned PLAs, PHAs exhibit good impermeability to water as well as rapid biodegradation properties, as shown in **Table 3**. They are a class of biopolymers which biodegrade by microorganisms. Additionally, they are considered thermoplastic and could be easily processed using existing molding and extrusion technologies known for petrochemical-based polymers [20]. Their rapid degradation under various environments is considered its main attribute in contrast with other alternatives, not to mention that they are considered as a sustainable substitute for being biocompatible and biorenewable as it originates from plant oils and sugars [27]. However, methods of synthesis are highly costly, and until a cost-effective method is derived, PHA commercialization would be limited and economically unjustified.
