Degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by aerobic sewage sludge.

The degradation of sheets of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (BIOPOL) by aerobic sewage sludge was analyzed. Degradation of the polymer was highly dependent on the pH of the culture medium and was maximal between pH 7 and pH 8.5. Below pH 6 and above pH 9 the degradation rate was very low. Agitation of the culture fluid had relatively little influence on the rates of degradation. 1.2 x 10(5) aerobic polymer-degrading bacteria per ml sewage sludge were identified by halo formation on solid poly(3-hydroxybutyrate) (PHB)-containing media. The number of PHB-degrading bacteria in other ecosystems amounted to 3.8 x 10(3) per ml sludge of a fresh-water lake, 9.2 x 10(5) per g garden-soil, 1.3 x 10(6) per g field-soil and 4.3 x 10(6) per g compost.