Degradation of phthalic acid and ortho-dimethyl phthalate ester by bacteria isolated from sewage sludge and its biochemical pathway

Abstract

Microbial degradation of phthalic acid (PA) and ortho-dimethyl phthalate ester (DMPE) under aerobic conditions was investigated using enrichment consortia of bacteria isolated from sewage sludge. Five morphologically distinctive microorganisms were isolated, purified and identified, and tested for the ability in degrading PA and DMPE. Comamonas acidovorans strain Fy-1 showed ability in degrading high concentration of PA (2 600 mg/L) within 48 h. Two reconstituted consortia of microorganisms, one composing of Pseudomonas fluorescens, P. aureofacien and Sphingomonas paucimobilis, and the other of S. paucimobilis and Xanthomonas maltophilia, showed ability in completely degradation of DMPE in 48～120 h. The degradation of DMPE by both consortia proceeded through formation of mono-methyl phthalate (MMP) and then PA before mineralization. This study suggests that high concentration of endocrine-disrupting chemicals PA and DMPE can be mineralized by consortia of indigenous microorganisms.