| Abstrakt: |
The degradation of samples of poly (3-hydroxybutyrate) [P(3HB)], copolymers of 3-hydroxybutyrate and 10 and 20% 3-hydroxyvalerate [P(3HB-co-3HV)], and poly (3-hydroxyoctanoate-co-3-hydroxydecanoate) [P(3H0-co-3HD)] in anaerobic sludge was investigated by gravimetry, changes in molecular weight and mechanical properties. After 123 days, the mass of P(3HB) decreased by 15%. P(3HB-co-3HV) showed 7 and 11% mass loss, while P(3H0-co-3HD) showed no change in mass. The average molecular weight of all samples decreased with incubation time but this decrease was not correlated to the loss of mass, and is to be attributed to abiotic hydrolysis. The tensile strength of the P(3HB) and P(3HB-co-3HV) samples decreased with incubation time, but elongation remained practically unchanged. By enumeration, it was shown that anaerobic P(3HB) degrading bacteria were enriched during the incubation period. An anaerobic bacterium LMG 16094, able to degrade P(3HB) and P(3HB-co-19% 3HV) in pure culture, but not P(3HB-co-97%3HV), P(3H0-co-3HD) or poly (ε-caprolactone), was isolated and characterized by fatty acid analysis. Its cells contained mainly straight chain, saturated and unsaturated fatty acids, with a high portion of fatty acids with 16 carbons, and did not contain hydroxylated or branched fatty acids. Its 16S rDNA gene sequence was found to be related to those of members of Clostridiumgroup I (Collinset al., 1994). In a simple in vitro test using strain LMG 16094 in pure culture, an extruded P(3HB-co-12% 3HV) film lost 10% of its initial mass within 21 days of anaerobic incubation. |
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