This protein degrades water-insoluble and water-soluble PHB to monomeric D(-)-3-hydroxybutyrate. [(3R)-hydroxybutanoate](n) + H2O = (3R)-hydroxybutanoate dimer + [(3R)-hydroxybutanoate](n-2) + H(+) [(3R)-hydroxybutanoate](n) + H2O = (3R)-hydroxybutanoate trimer + [(3R)-hydroxybutanoate](n-3) + H(+) [(3R)-hydroxybutanoate](n) + H2O = (R)-3-hydroxybutanoate + [(3R)-hydroxybutanoate](n-1) + H(+) [(3R)-hydroxybutanoate](n) + H2O = (3R)-hydroxybutanoate pentamer + [(3R)-hydroxybutanoate](n-5) + H(+) [(3R)-hydroxybutanoate](n) + H2O = (3R)-hydroxybutanoate tetramer + [(3R)-hydroxybutanoate](n-4) + H(+) Belongs to the AB hydrolase superfamily. Lipase family.