Effect of glycerol and its analogs on polyhydroxyalkanoate biosynthesis by recombinant Ralstonia eutropha: A quantitative structure-activity relationship study of chain transfer agents

Triglycerides such as plant and vegetable oils are desirable feedstock for the fermentative production of polyhydroxyalkanoate (PHA) because the weight yield of PHA from triglycerides is higher than that obtained from sugars. However, glycerol, a multi-hydroxy component of triglyceride, is known to function as a chain transfer (CT) agent in PHA polymerization, resulting in the formation of low-molecular-weight PHA. In this study, we evaluated how glycerol alters the molecular weight of PHA using recombinant Ralstonia eutropha as a practical host for PHA production. We demonstrated that glycerol has the ability to reduce molecular weight of PHA, even as a component of triglyceride. Furthermore, various alcohols that are structurally related to glycerol were examined for their reducing abilities to perform a quantitative structure-activity relationship (QSAR) study. It was found that alcohols with higher hydrophobicity (log P) exhibited higher reducing ability for PHA molecular weight. Glycerol, a less hydrophobic alcohol, was able to reduce PHA molecular weight; however, the efficacy was relatively weak among the examined alcohols.