Phthalate esters detected in various water samples and biodegradation of the phthalates by microbes isolated from river water

Phthalate esters (PEs), especially di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were detected in various water samples such as river water, well water and tap water. On degradation tests of PEs, Tempaku River water degraded almost 100% of diethyl phthalate (DEP), di-isobutyl phthalate and DBP, and approximately 70% of DEHP. All eight isolates from Tempaku River water (R1-R7, D1) did not degrade dimethyl phthalate (DMP), but showed biodegrading ability for the other PEs. The DBP-degrading ability was particularly high for the isolates R1-R3 and D1 of Acinetobacter iwoffii. Crude enzyme solutions prepared from bacterial cells of these isolates showed a higher degrading activity for DEHP compared with that for microbially-degradable DBP. Particularly high DEHP-degrading activity was found for crude enzyme solutions of the isolate D1. As metabolites from the river water and bacterial isolates, DMP and an unknown diester were produced from DEP. DMP, DEP, monomethyl phthalate, monobutyl phthalate (MBP) and an unknown diester were produced from DBP. DBP, DEP, DMP and an unknown diester were produced from DEHP. As metabolites by the crude enzyme solutions, DMP, MBP and an unknown diester derivative were produced from DBP. DBP, mono-(2-ethylhexyl) phthalate and an unknown diester derivative were produced from DEHP. Diesters with shortened alkyl carbon chains were also found as metabolites by the isolates and their crude enzyme solutions. The results suggest that the alkyl chains in the diesters are also decomposed in addition to monoester formation from DBP or DEHP at the first step reported for animals and some types of bacteria.