Characterisation of a thermostable catechol-2,3-dioxygenase from phenanthrene-degradingPseudomonas sp. strain ZJF08

Abstract

Four strains with high phenanthrene-degrading ability were isolated from petroleum badly polluted soil. The strainPseudomonas sp. ZJF08 demonstrated the highest rate of degradation (138. 1 mg·L−1·day−1) among them and degraded 97.1% of the phenanthrene in one week. The activities of two key enzymes of ZJF08, polycyclic aromatic hydrocarbon dioxygenase and catechol-2,3-oxygenase (C23O), were also assayed during the degradation of phenanthrene. Both of them reached their maximums on the 2nd day of degradation. The C23O gene (C7) ofPseudomonas sp. ZJF08 was cloned and expressed inEscherichia coli, and its gene product was purified by a Ni-NTA-agarose column. The optimum temperature for the purified C23O was 40°C at pH 7.5 and the C23O activity could be still detected when the temperature reached 70°C. The results showed that the C23O fromPseudomonas sp. strain ZJF08 exhibited better thermostability than its homologs reported.