Effect of monomer composition and composition distribution on enzymatic degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The enzymatic degradation of solution-cast films of bacterial poly(3-hydroxybutyrate) [PHB] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB-co-HV)] with various comonomer compositions and with various composition distributions was investigated by using PHB depolymerase purified from Alcaligenes faecalis T1. We prepared P(HB-co-HV) samples with different composition distribution by fractional precipitation of P(HB-co-HV). The rate of enzymatic degradation of the P(HB-co-HV) samples showed a linear increase with the HV content up to about 30 mol-%. Although the crystalline phase structure of the P(HB-co-HV)s changes depending on the composition distribution, their enzymatic degradability is independent of the composition distribution. The comonomer composition distribution and the crystalline phase structure have little effect on the rate of enzymatic degradation. The rate of enzymatic degradation of P(HB-co-HV) can be predicted on the basis of its average monomer composition.