Biodegradation of poly(3-hydroxyalkanoic acids) fibers and isolation of poly(3-hydroxybutyric acid)-degrading microorganisms under aquatic environments

Biodegradabilities of poly[(R)-3-hydroxybutyric acid-co-14mol%(R)-3-hydroxy valeric acid] (P(3HB-co-14%3HV)) monofilament fibers were evaluated at 25 d egrees C for 28 days by monitoring the time-dependent changes in the bioche mical oxygen demand (BOD) and weight-loss (erosion) of fibers under aerobic conditions in a temperature-controlled reactor containing natural waters f rom various aquatic environments (seawater, lake freshwater and river fresh water in Japan). Two types of fibers with different diameters (213 and 493 mu m) were used in this test. The biodegradabilities of fibers decreased in the following order: river freshwater > lake freshwater > seawater. By ana lyses of scanning electron microscopy and X-ray diffraction of eroded fiber s, it has been concluded that the biodegradation proceeded from amorphous r egions on the surface of fibers by the function of microorganisms in freshw ater or seawater. In addition, 13 strains of P(3HB)-degrading bacteria were isolated from different sources of seawater and identified. Majority of is olates grew well on P(3HB) or P(3HB-co-14%3HV) as sole carbon source and ex creted extracellular polyhydroxybutyrate (PHB) depolymerases. (C) 1998 Else vier Science Ltd. All rights reserved.