Determination of polyhydroxyalkanoates in activated sludge by ion chromatographic and enzymatic methods

Two new detection methods for the determination of poly-beta-hydroxybutyrat e (PHB) and -valerate (PHV) are described. Both methods are based on depoly merization of PHB/PHV to 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV ). Depolymerization was achieved by either propanolic or hydrolytic digesti on. Propanolic digestion transformed commercial PHB/PHV stoichiometrically into 3HB/3HV and yielded apparently complete recoveries of bacterial PHB/PH V from activated sludge. Hydrolytic digestion was suitable only for PHB det ermination. For quantification of 3HB and 3HV directly from digested sludge , a method based on ion-exchange chromatography and conductivity detection was developed (IC-method). Alternatively, the total of 3HB and 3HV was quan tified using a commercial enzymatic test kit and colorimetric detection (en zyme method). Both detection methods are easier to perform than previous me thods and are suitable for complex matrices such as activated sludge. The I C-method is recommended for high sample throughputs or if distinction betwe en PHB and PHV is essential. Enzymatic detection is recommended if a few sa mples per day have to be measured immediately or if an ion chromatograph is unavailable. (C) 1999 Elsevier Science B.V. All rights reserved.