Identification of a poly(3-hydroxybutyrate)-degrading bacterium isolated from coastal seawater in Japan as Shewanella sp.

A poly[(R)-3-hydroxybutyrate] [P(3HB)]-degrading bacterium (strain JKCM-AJ-6,1α) was isolated from coastal seawater near the port of Yaizu, Suruga Bay, Japan. The strain grew well in a marine mineral medium supplemented with P(3HB) powder as the sole carbon source. Phylogenetic analysis revealed that the strain JKCM-AJ-6,1α belonged to the genus Shewanella. The isolate was unable to grow at temperatures above 50 °C, and the optimum range of growth temperatures was 30 °C-37 °C; however, the optimum temperature for degradation of P(3HB) was 15 °C. The maximum specific growth rate (μ = 1.0 h−1) was attained at a NaCl concentration of 0.2 M, but the strain was able to grow even in the presence of 0.8 M NaCl. This suggests that the strain is a typical marine bacterium. This is the first report showing P(3HB) depolymerase activity in a member of the genus Shewanella. It is concluded that the genus Shewanella may be one of the key bacterial groups involved in the P(3HB) cycle in marine environments.