Degradation of Biodegradable Plastics in Seawater

Abstract

The performance of biodegradable plastics in seawater at various locations was examined. The seawater was sampled in the pier of Tokyo University of Fisheries, the mouth of Tama river, the mouth of Edo river, the mouth of Kyuedo river, Sagami bay and the offing in Boso peninsula. In this study, we used two samples of biodegradable plastics, polycaprolactone (PCL), and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) [p (3HB/V)]. The biodegradability of their films in seawater was assessed by monitoring the time-dependent changes in the biochemical oxygen demand (BOD). The films were rapidly degraded in seawater sampled in Tokyo bay and BOD-biodegradability of their films was 42 and 92% for 7 and 23days respectively. BOD-biodegradability of films in seawater sampled in other area was Iower than that sampled in Tokyo bay. The study using the scaming electron microscope showed the films decomposed by the microorganism. The PCL-degrading microorganisms were isolated from the seawater and designated R-1, R-2 and R-3. Physiological and phylogenetic characters of these microorganisms were examined. These results show that strain R-1 was identified as Pseudomonas studomons, and strains R-2 and R-3 belong to the genus Pseudomonas. Biodegradation of PCL monofilament fiber by isolated bacteria, strain R-1 was investigated. Tensile strength of PCL monofilament was rapidly reduced to 50% for 2 days.