Participates in the degradation of poly-3-hydroxybutyrate (PHB). It works downstream of poly(3-hydroxybutyrate) depolymerase, hydrolyzing D(-)-3-hydroxybutyrate oligomers of various length (3HB-oligomers) into 3HB-monomers. (3R)-hydroxybutanoate dimer + H2O = 2 (R)-3-hydroxybutanoate + H(+) Inhibited by diisopropylfluorophosphate (DFP). Optimum pH is 7-8.5. Lipid metabolism; butanoate metabolism. Belongs to the D-(-)-3-hydroxybutyrate oligomer hydrolase family.