| The biodegradation of poly(3-hydroxyalkanoates) (PHAs) under different anaerobic conditions was examined using the techniques of anaerobic microbiology and analytical chemistry. Methanogenic environments sampled included sewage sludge, pond sediment and rumen fluid. Nitrate-reducing consortia were established using activated sludge. Attempts were made to establish ferric iron- and sulfate-reducing consortia from sewage sludge and spring water, yet it could not be demonstrated that the mixed cultures were capable of degrading PHAs.; PHAs were shown to be biodegradable in activated sludge under nitrate-reducing conditions. A positive correlation between carbon dioxide production and nitrate reduction was demonstrated. Nitrous oxide accumulated as the main N-containing end product of nitrate reduction. The amount of PHAs in activated sludge cultures decreased approximately 20% within 40 days of incubation.; PHAs were fermented to methane and carbon dioxide within 16 days by an anaerobic sewage sludge consortium. The cultures adapted quickly to metabolize the PHAs, and between 83 and 96% of the substrate carbon was transformed to methane and carbon dioxide. PHAs were fermented to methane and carbon dioxide after 10 weeks by a sediment consortium as well, however, only 43 and 57% of the substrate carbon was transformed to methane.; Although it could not be demonstrated that PHAs were biodegraded by a rumen fluid consortium, a facultative anaerobic bacterium, identified as a Staphylococcus sp., that could grow on PHAs was isolated from rumen fluid. A depolymerase was secreted into the culture fluid during both the exponential and stationary growth phase when PHA granules served as carbon substrate. The majority of the depolymerase activity was not detected in the culture supernatant but was found to be associated with the granules. |
