Evaluation of Blended Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Properties Containing Various 3HHx Monomers

Polyhydroxyalkanoate (PHA), specifically poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyhexanoate) (P(3HB-<i>co</i>-3HHx), PHBHHx) with physical properties governed by the 3-hydroxyhexanoate (3HHx) mole fraction, is a promising bioplastic. Although engineered strains used to produce P(3HB-<i>co</i>-3HHx) with various 3HHx mole contents and fermentation techniques have been studied, mass production with specific 3HHx fractions and monomers depends on the batch, supply of substrates, and strains, resulting in the time-consuming development of strains and complex culture conditions for P(3HB-<i>co</i>-3HHx). To overcome these limitations, we blended poly(3-hydroxybutyrate) [(P(3HB), produced from <i>C. necator</i> H16] and P(3HB-<i>co</i>-20 mol%3HHx) [from <i>C. necator</i> 2668/pCB81] to prepare films with various 3HHx contents. We evaluated the molecular weight and physical, thermal, and mechanical properties of these films and confirmed the influence of the 3HHx monomer content on the mechanical and thermal properties as well as degradability of the blended P(3HB-<i>co</i>-3HHx) films containing various 3HHx mole fractions, similar to that of original microbial-based P(3HB-<i>co</i>-3HHx). Moreover, the degradation rate analyzed via <i>Microbulbifer</i> sp. was >76% at all blending ratios within 2 days, whereas a weaker effect of the 3HHx mole fraction of the blended polymer on degradation was observed. P(3HB-<i>co</i>-3HHx) could be produced via simple blending using abundantly produced P(3HB) and P(3HB-<i>co</i>-20 mol%HHx), and the resulting copolymer is applicable as a biodegradable plastic.