Biodegradation of P(3HB- co-4HB) powder by Pseudomonas mendocina for preparation low-molecular-mass P(3HB- co-4HB)

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 (¹H 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 ¹H 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.