Stimulated by the commercial availability of bacteriologically produce
d polyesters such as poly[(R)-3-hydroxybutyric acid], and encouraged b
y the discovery of new constituents of polyhydroxyalkanoic acids (PHA)
, a considerable body of knowledge on the metabolism of PHA in microor
ganisms has accumulated. The objective of this essay is to give an ove
rview on the biodegradation of PHA. The following topics are discussed
: (i) general considerations of PHA degradation, (ii) methods for iden
tification and isolation of PHA-degrading microorganisms, (iii) charac
terization of PHA-degrading microorganisms, (iv) biochemical propertie
s of PHA depolymerases, (v) mechanisms of PHA hydrolysis, (vi) regulat
ion of PHA depolymerase synthesis, (vii) molecular biology of PHA depo
lymerases, (viii) influence of the physicochemical properties of PHA o
n its biodegradability, (ix) degradation of polyesters related to PHA,
(x) biotechnological aspects of PHA and PHA depolymerases.