**2.2 Classification of PHA**

PHAs are classified into three classes short, medium, or long chain length (scl, mcl, and lcl), respectively. It is based on the number of carbon atoms as short-chain-length PHA (scl-PHA), medium-chain-length PHA (mcl-PHA), and long-chain length PHA (lcl-PHA). Scl-PHA refers to PHA comprised of monomers having 5 or fewer carbon atoms [19]. These include 3-hydroxybutyrate and 3-hydroxyvalerate. The mcl-PHA is comprised of monomers having 6 to 14 carbon atoms. These include 3 hydroxyhexanoate, 3-octanoate, and 3-hydroxydecanoate. The lcl-PHA, which is uncommon and least studied, consists of monomers with more than 14 carbon atoms [20] (**Figure 1**).

**Figure 1.** *General structures of polyhydroxyalkanoates.*
