Isolation and molecular identification of landfill bacteria capable of growing on di-(2-ethylhexyl) phthalate and deteriorating PVC materials.

Waste materials containing Di-(2-ethylhexyl) phthalate (DEHP), a suspected endocrine disruptor and reasonably anticipated human carcinogen, are typically disposed of in landfills. Despite this, very few studies had been conducted to isolate and identify DEHP-degrading bacteria in landfill leachate. Therefore, this study was conducted to isolate and characterize bacteria in landfill leachate growing on DEHP as the sole carbon source and deteriorating PVC materials. Four strains LHM1, LHM2, LHM3 and LHM4, not previously reported as DEHP-degraders, were identified via 16S rRNA gene sequence. Gram-positive strains LHM1 and LHM2 had a greater than 97% similarity with Chryseomicrobium imtechense MW 10(T) and Lysinibacillus fusiformis NBRC 15717(T), respectively. Gram-negative strains LHM3 and LHM4 were related to Acinetobacter calcoaceticus DSM 30006(T) (90.7% similarity) and Stenotrophomonas pavanii ICB 89(T) (96.0% similarity), respectively. Phylogenetic analysis also corroborated these similarities of strains LHM1 and LHM2 to the corresponding bacteria species. Strains LHM2 and LHM4 grew faster than strains LHM1 and LHM3 in the enrichment where DEHP was the sole carbon source. When augmented to the reactors with PVC shower curtains containing DEHP, strains LHM1 and LHM2 developed greater optical densities in the solution phase and thicker biofilm on the surfaces of the shower curtains.

PVC biodeterioration and DEHP leaching by DEHP-degrading bacteria.

Newly isolated, not previously reported, di-(2-ethylhexyl) phthalate (DEHP)-degraders were augmented to assess their role in polyvinyl chloride (PVC) shower curtain deterioration and DEHP leaching. The biofilms that developed on the surfaces of the bioaugmented shower curtains with Gram-positive strains LHM1 and LHM2 were thicker than those of the biostimulated and Gram-negative strain LHM3-augmented shower curtains. The first derivative thermogravimetric (DTG) peaks of the bioaugmented shower curtains with the Gram-positive bacteria were observed at ~287°C, whereas the control and Gram-negative strain LHM3-augmented shower curtains were detected at ~283°C. This slight delay in the first DTG peak temperature is indicative of lower plasticizer concentrations in the shower curtains that were bioaugmented with Gram positive bacteria. Despite bioaugmentation with DEHP-degraders, aqueous solutions of the bioaugmentation reactors were not DEHP-free due probably to the presence of co-solutes that must have supported microbial growth. Generally, the bioaugmented reactors with the Gram-positive strains LHM1 and LHM2 had greater aqueous DEHP concentrations in the first-half (<3 wk) of the biodeterioration experiment than the biostimulated and strain LHM3-augmented reactors. Therefore, strains LHM1 and LHM2 may play an important role in DEHP leaching to the environment and PVC biodeterioration.