Fermentation, biodegradation and tensile strength of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) synthesized by Delftia acidovorans

This study discusses poly(3-hydroxybutyrate-co-4-hydroxybutyrate) that is produced by Delftia acidovorans bacteria in fed-batch cultures from various carbon sources. The experimentally determined optimal fed-batch culture conditions are as follows: pH: 7.0, incubation temperature: 26 °C, incubation time: 72 h, and concentration of carbon source: 10 g/L. The maximum 4HB unit composition of P(3HB-co-4HB) obtained using the fed-batch culture with a cell concentration of about 2.5 g/L was 94 mol% although the P(3HB-co-4HB) content remained low, at around 13 wt%. The extent of the enzymatic degradation of P(3HB-co-4HB) was determined by involved PHB depolymerase and lipase. The tensile strength of P(3HB-co-4HB) markedly decreased during 2 h of degradation by PHB depolymerase, whereas that of P(3HB-co-4HB) degraded by lipase for 50 h was at least 3 MPa.