Abstract
Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a biodegradable plastic that is extensively utilized in many fields. In this work, P(3HB-co-4HB) powder was degraded by Pseudomonas mendocina for the preparation of low-molecular-mass (LMW) P(3HB-co-4HB). After degradation, the remaining P(3HB-co-4HB) powder was analyzed via gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance ((1)H NMR) spectroscopy. The degradation of P(3HB-co-4HB) by P. mendocina occurred in two stages: the fast degradation stage (0-8 h) and the slow degradation stage (8-24 h). GPC analysis showed that the molecular weight of P(3HB-co-4HB) gradually decreased with degradation time. After 24 h of degradation, the weight-average molecular weight of P(3HB-co-4HB) was reduced to 4-5 kDa. DSC and XRD analyses both verified that the degree of crystallinity decreased with prolonged degradation time. The melting temperature of the degraded powder, however, remained unchanged. FTIR and (1)H NMR analyses of the degraded powder showed that no new material was produced during degradation. Thus, the degradation of P(3HB-co-4HB) by P. mendocina could be used to produce LMW P(3HB-co-4HB) for use in various applications, such as the synthesis of amphiphilic block copolymers.