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A gram negative isolate designated JDC-41 was obtained from river sludge using mixtures of phthalate esters as the sole source and energy. The isolate was identified as Ochrobactrum sp. based on its 16S rRNA gene sequence. Over 87% of supplied di-n-butyl phthalate (DBP) was degraded by JDC-41 in a pH neutral mineral salts medium at 30 degrees C within 48 h. Increased DBP (50-500 mg/L) in the culture correspondingly increased degradation half-life from 3.83 to 18.12 h. DBP induced cells more rapidly degraded DBP.

Four aerobic bacterial strains capable of utilizing di-n-butyl phthalate (DBP) as the sole source of carbon and energy were isolated from river sediments. Based on the morphology, biochemical characterization, and 16S rRNA gene sequence analysis, they were identified as Gordonia sp. The optimal conditions for DBP degradation by these strains were found to be pH 7.0, 30°C, and stirring at 175 rpm. These four strains could degrade, respectively, 96, 98, 98, and 78% of DBP (400 mg l -1 ) as well as dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-octyl phthalate (DOP), di-isooctyl phthalate (DIOP), and di-isononyl phthalate (DINP). Furthermore, partial sequences of the gene for 3,4-phthalate dioxygenase were obtained from all four strains. To our knowledge, this is the first time that the 3,4-phthalate dioxygenase gene has been successfully cloned from Gordonia sp.

A gram negative bacterium, named JDC-16, which can grow well on the substrate of phthalic acid esters (PAEs) as the sole source of carbon and energy, was isolated from river sludge. Based on the morphology, physiological and biochemical properties and analysis of 16S rRNA gene sequence, it was preliminarily identified belonging to the genus Acinetobacter. The result of substrates utilization range indicates that strain JDC-16 can utilize a variety of phthalates except for diisononyl phthalate (DINP). The degradation tests using diethyl phthalate (DEP) as the model compound show that the optimal pH and temperature for DEP degradation by Acinetobacter sp. JDC-16 is 8.0 and 35 ℃, respectively. Meanwhile, degradation kinetics under various initial concentrations of DEP reveals that substrate depletion curves fit well with the modified Gompertz model with high correlation coefficient (R 2 ＞0.99). Furthermore, the substrate induction test indicates that DEP-induction can apparently shorten the lag phase and enhance the degradation rate. This work highlights the potential of this isolate for bioremediation of phthalates-contaminated environments.