Ishigaki, T, Sugano, W, Ike, M, Kawagoshi, Y, Fukunaga, I, Fujita, M
Department of Environmental Engineering, Osaka University, Japan.
tomonori.ishigaki@env.eng.osaka-u.ac.jp
Abstract:
In order to assess the degradability of plastics in solid waste disposal
landfill sites, microbial populations capable of degrading five kinds of
plastic-constituting polymers, poly epsilon-caprolactone (PCL), polylactic acid
(PLA), polyethylene glycol (PEG), poly-beta-hydroxybutyrate (PHB) and cellulose
acetate (CA), in a sea-based solid waste disposal site were investigated.
Enumeration of aerobic and anaerobic polymers-degrading microorganisms (PDMs)
was performed against to total 8 leachate samples, which were seasonally
collected from the facultative pretreatment pond and the aerated lagoon. Both
aerobic and anaerobic PDMs for natural polymers, PHB and CA, were found in all
of the samples, while those for chemically-synthesized polymers, PCL, PLA and
PEG, could not be always detected. In most cases, the ratios of the PHB- and
CA-degraders to the heterotrophic bacterial population were more than 0.1%. On
the other hand, the ratios of PCL-, PLA- and PEG-degraders were often much
lower. These data indicate that the plastics degradation potential is commonly
present in the studied disposal site, and that the degradation potential for
plastics composed of chemically-synthesized polymers is inferior to that of
natural polymers. Population sizes of the PDMs correlated to those of
heterotrophic bacteria, and the counts of aerobic heterotrophic bacteria and
PDMs in the aerated lagoon tended to be higher than those of anaerobic ones,
indicating that the aeration of the leachate resulted in the activation of
growth of whole aerobic microbial community including the PDMs.
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