Abstract We demonstrate a novel strategy to produce ( R )-3-hydroxybutyric acid [( R )-3-HB] using Pseudomonas sp. DS1001a or its extracellular poly (3-hydroxybutyrate) (PHB) depolymerase. While approximately 77.8% PHB was degraded by Pseudomonas sp. DS1001a after 12 h of cultivation, only 1.555 g/l of 3-HB monomer was produced because of assimilation by the strain. About 8.58 g/l ( R )-3-HB was obtained after 8 h of incubation using extracellular PHB depolymerase from Pseudomonas sp. DS1001a. The optimal temperature and pH of PHB depolymerase were 50 °C and 8, respectively. CaCO 3 increased ( R )-3-HB yields to 23.97 g/l by stabilizing the pH of the reaction system. High yields of the ( R )-3-HB product and the low cost of the medium and CaCO 3 indicate the feasibility of bioconversion of low-value PHB waste or industrial leftovers into high-value ( R )-3-HB using extracellular PHB depolymerase.