An enzymatic process and system are disclosed for producing homogeneous chain length poly hydroxyalkanoate monomers and/or polymers having a chain length of at least eight carbons from a long-chain fatty acid or precursor thereof. The process also results in specific homogenous chain length polyhydroxyalkanoate monomers and/or polymers. The long-chain fatty acid or precursor thereof can be contacted in vitro with an enzyme or a mixture of enzymes to produce the homogeneous chain length polyhydroxyalkanoate.