[Acclimating, screening of dominant bacteria for degrading phthalic acid esters and study on its degradation]

To define the method of acclimating isolating and screening of dominant bacteria for phthalic acid esters biodegradation and study their plasmids.

Active sludge aeration and method of density gradient were used to acclimate the sludge. The concentration of the carbon source including DMP, DEP and DBP was increased step by step in continuous eight weeks. The biodegradation test on PAEs was conducted after bacteria isolation. The dominant bacterium was identified and its degradation plasmid was extracted.

Five strains of dominant bacteria were screened. Two strains' degradation rates to DMP, DEP, DBP in 7 days could reach to 99.9%, 98.6%, 99.2% (No.4 bacterium) and 87.5%, 99.1%, 98.3% (No. 1 bacterium), respectively. However, their plasmids could not be found. The bacterium which could have better degradation efficiency was identified as Pasteurella multocida.

The dominant bacteria could be got through density gradient acclimatization in the active sludge aeration basin. The biodegradation gene fragment of the two strains could exist in its genome but not in plasmid.