Phthalic acid esters (PAEs) are mainly used as plasticizers and result in serious environmental contamination worldwide. Microbial biodegradation becomes an efficient strategy for PAE elimination. In the current study, the PAE-degrading strainGordoniasp. LUNF6 was isolated from contaminated soil. Strain LUNF6 can efficiently degrade DBP in a wide range of temperatures, pH values, and salinity levels. This strain is also capable of degrading 11 types of PAEs and displays remediation potential in wastewater. The complete genome of strain LUNF6 was sequenced to determine its efficient degradation performance. Its genome comprises a chromosome (3,971,257 bp) and a plasmid (78,813 bp). After gene function annotation, the complete PAE degradation pathway was proposed. The gene of monoalkyl PAE hydrolase MphGd2 was cloned and heterologously expressed. The protein of MphGd2 was purified by infinity chromatography, and we hydrolyzed MBP to produce PA. These results reveal the molecular mechanism of PAE degradation by strain LUNF6, which will contribute to the application of strain LUNF6 and hydrolase MphGd2 in bioremediation.
Di-(2-ethylhexyl) phthalate (DEHP), the most extensively used phthalate acid esters (PAEs), poses a potential risk to human and environment. A novel bacterial strain , Rhodococcus sp. LW-XY12, with efficient PAE-degrading capability, was isolated from activated sludge. Strain LW-XY12 could degrade 96.91 ± 0.68% of DEHP (500 mg L −1 ) within 32 h. The degradation curves of DEHP (50–1500 mg L −1 ) and PAE mixture (500 mg L −1 each) fitted well with the modified Gomperz kinetics model. DEHP metabolic pathway was reconstructed by using genome annotation and metabolic intermediate analyses. The DEHP metabolic pathway might comprise de-esterification and β-oxidation. Homologous modeling and molecular docking analysis revealed that DEHP and MEHP (mono-(2-ethylhexyl) phthalate) could be bound to putative carboxylesterase (KXC42_04905) via hydrogen bonding and hydrophobic interaction. A conserved catalytic triad (Ser195-Glu319-His412) might act as an active protein pocket and catalyze the hydrolysis of DEHP. Carboxylesterase (KXC42_04905) could hydrolyze ester bond and a possible mechanism underlying ester bond hydrolysis catalyzed by the carboxylesterase was proposed. Protocatechuate 3,4-dioxygenase, 3-oxoadipate CoA-transferase, benzoate 1,2-dioxygenase, catechol 1,2-dioxygenase, and catechol 2,3-dioxygenase transcripts were detected and significantly up-regulated under DEHP induction. This study sheds light on the functional genes associated with DEHP degradation and metabolic mechanism in this versatile bacterium for degradation of PAEs.
危险品化学品经营许可证（带存储）