These monomers can then be converted by genetically modified bacteria to produce PHAs . Depending on the substrate structure and the enzymes involved, a wide range of bacterial polymers can be obtained, differentiated by their number of carbons per repeat unit . Among them, medium side-chain length (mcl) PHAs have repeat units of 6 to 12 carbons, such as poly(3-hydroxy-octanoate) (PHO). The chemical structure of PHO is shown in Figure .