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Strain YZ-1 was isolated from activated sludge and identified as Ochrobactrum anthropi. This strain was capable of degrading pyrethroids pesticides, suggesting the presence of degrading enzymes. In the present study, a novel esterase gene pytZ was cloned from the genomic library of YZ-1 successfully. The pytZ contained an open reading frame of 606bp encoding a pyrethroid-hydrolyzing carboxylesterase. Deduced amino acid sequence showed moderate identities (39-59%) with most homologous carboxylesterase, except a putative carboxylesterase from O. anthropi ATCC 49188 with the highest identity of 85%. Phylogenetic analysis revealed that PytZ belonged to esterase VI family. The gene pytZ showed no any sequence similarity with reported pyrethroid-hydrolyzing genes and was a new pyrethroid-degrading gene. PytZ was expressed in Escherichia coli BL21 (DE3) and purified using Ni-NTA Fast Start. PytZ was able to degrade various pyrethroids. The optimal temperature and pH were 35°C and 7.5. This enzyme was very stable over a wide range of temperature and pH. No cofactors were required for enzyme activity. Broad substrate specificity, high enzyme activity, and the favorable stability make the PytZ a potential candidate for the detoxification of pyrethroid residues in biotechnological application.

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One bacterial strain, YC-RL2, isolated from petroleum-contaminated soil, could utilize environmental hormone Di(2-Ethylhexyl) phthalate (DEHP) as a sole carbon source for growth. Strain YC-RL2 was identified as Gordonia alkanivorans by 16S rRNA gene analysis and Biolog tests. The effects of environmental factors which might affect the degrading process were optimized at 30 °C and pH 8.0. Strain YC-RL2 showed superior halotolerance and could tolerate up to 0-5% NaCl in trace element medium supplemented with DEHP, although the DEHP degradation rates slowed as NaCl concentration increased. It also showed an outstanding performance in a wide range of pH (6.0-11.0). Meanwhile, strain YC-RL2 was able to withstand high concentrations of DEHP (from 100 to 800 mg/L), and the degradation rates were all above 94%. The DEHP intermediates were detected by HPLC-MS, and the degradation pathway was deduced tentatively. DEHP was transformed into phthalic acid (PA) via mono (2-ethylhexyl) phthalate (MEHP), and PA was further utilized for growth via benzoic acid (BA). The enzyme expected to catalyze the hydrolysis of MEHP to PA was identified from strain YC-RL2. Further investigation found that the enzyme could catalyze the transformation of a wide range of monoalkyl phthalates to PA. This study is the first report about species G. alkanivorans which could degrade several kinds of phthalic acid esters (PAEs), and indicates its application potential for bioremediation of PAE-polluted sites.